Nolte’s The Human Brain in Photographs and Diagrams [5th Edition] 0323598161, 9780323598170, 9780323598163

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5

TH

EDITION

Nolte’s THE

HUMAN BRAIN IN PHOTOGRAPHS AND DIAGRAMS Todd W. Vanderah, PhD Professor and Chair of Pharmacology Department of Pharmacology, Anesthesiology, and Neurology University of Arizona, College of Medicine Tucson, Arizona

1600 John F. Kennedy Blvd. Ste 1800 Philadelphia, PA 19103-2899

NOLTE’S THE HUMAN BRAIN IN PHOTOGRAPHS AND DIAGRAMS, FIFTH EDITION

ISBN: 978-0-323-59816-3

Copyright © 2020 by Elsevier, Inc. All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Details on how to seek permission, further information about the Publisher’s permissions policies and our arrangements with organizations such as the Copyright Clearance Center and the Copyright Licensing Agency, can be found at our website: www.elsevier.com/permissions. This book and the individual contributions contained in it are protected under copyright by the Publisher (other than as may be noted herein).

Notice Practitioners and researchers must always rely on their own experience and knowledge in evaluating and using any information, methods, compounds or experiments described herein. Because of rapid advances in the medical sciences, in particular, independent verification of diagnoses and drug dosages should be made. To the fullest extent of the law, no responsibility is assumed by Elsevier, authors, editors or contributors for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions, or ideas contained in the material herein. Previous editions copyrighted 2013, 2007, 2000, 1995. Library of Congress Control Number: 2018954443

Content Strategist: Marybeth Thiel Publishing Services Manager: Catherine Jackson Senior Project Manager: Amanda Mincher Design Direction: Amy Buxton

Printed in China Last digit is the print number: 9 8 7 6 5 4 3 2 1

To Our Students Whose enthusiasm excites me to be a better teacher Whose inquisitiveness drives me to dig deeper for answers Whose joy to learn thrusts my dedication towards the educational mission Whose rich personalities demonstrate how the human brain has incredible capability and compassion -John Nolte, PhD, Todd W. Vanderah, PhD, and Jay B. Angevine Jr., PhD

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IN MEMORIAM

When it comes to learning the anatomy and basic functions of the human nervous system, John “Jack” Nolte has played a role as an author and/or a professor for hundreds of thousands of students, residents, and physicians. Jack viewed the human brain as an endlessly fascinating playground that is forever changing. His

lifetime goal was not only to educate students but to educate future teachers as well. He continually scoured the primary literature and behaved with childhood excitement when discovering new explanations for human brain function. His own love and excitement for the nervous system would naturally bleed over to his students and colleagues, encouraging them to explore and question the human nervous system. In working with Jack for over 15 years, my career and take on life changed from teaching as a “job” to teaching as an enjoyable hobby with benefits. His ability to make teaching fun, telling jokes and giving examples, led to an enriched student environment that resulted in students wanting more. Our meetings most often included discussions of how we could better educate students. Jack was on the cutting edge of designing “case-based” instruction, showing videos of patients for teaching purposes, having patients present in the classroom, and pushing ideas of working and taking exams as groups, using innovative technology, including the virtual brain and interconnected vocabulary terms across multiple fields of science. Jack’s desire to create a textbook that was cutting edge yet to the point for learning purposes was his continual love. He shared with me chapters, images, and novel ideas while writing the next edition to continually produce a product that students would enjoy. Our time together was not all work. Although most know him as a professor of the nervous system, Jack also enjoyed playing handball, woodworking, traveling, cooking, wonderful deep red wines, a martini with blue cheese olives, and the joy of eating oysters (things that often appeared in his textbook as examples of nervous system function). In closing, I dedicate this new edition to my teacher, colleague, and friend. I dearly miss Jack’s enthusiasm for teaching, his humor, his friendship, and of course his infamous Birkenstocks.

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P R E FA C E Learning about the functional anatomy of the human central nervous system (CNS) is usually a daunting task. Structures that interdigitate and overlap in three dimensions contribute to the difficulty, as does a long list of intimidating names, many with origins in descriptive terminology derived from Latin and Greek. Here we have attempted to make the task a little easier by presenting a systematic series of whole-brain sections in three different sets of planes (coronal, sagittal, and axial—similar to what is seen in medical imaging), by relating these sections to three-dimensional reconstructions, and by trying to restrain ourselves when indicating structures. Unlabeled photographs are presented throughout the book, juxtaposed with faded-out versions of the same photographs with important structures outlined and labeled. This circumvents the common need to mentally superimpose a labeled drawing on a photograph or to inspect a photograph through a thicket of lead lines. Photos of the CNS are comprehensive sets in each plane; sections illustrating major structures or major transitions are shown in greater detail and at a higher magnification. Every labeled structure is discussed briefly in an illustrated glossary at the end of the book. For this edition, minor adjustments were made to sections and photographs throughout the book; the functional pathways in chapter 8 were redone in color; an important new imaging modality (diffusion tensor imaging) was added to Chapter 9; and a number of new illustrations were added to the glossary. Chapter 10 is brand new in this edition as an introduction to neuropathology. Common types of CNS derived tumors and

neuro-diseases/disorders are displayed as representative images of what might be detected upon diagnosis. The methods used in this book inevitably involve compromises. We labeled only structures that we believe are important for the knowledge base of undergraduate and professional students, and we omitted others dear to our hearts but perhaps not critical for these students. Hence the fasciola cinerea so prominent in Figure 7.8 is not labeled, and the indusium griseum is mentioned only briefly in a footnote. In addition, explicitly outlining structures required some simplifications, and complex entities are sometimes indicated more simply as single structures. We think the resulting pedagogical utility for students justifies these anatomical liberties. Current technological methods allowed us to approach the construction of this atlas differently than we could have when it was first discussed. All the photographs of brains and sections used in the book were retouched digitally. Mounting medium, staining artifacts, and small cracks, folds, and scratches were removed from the digitized versions of the sections. The profiles of many small blood vessels were removed as well. The color balance was changed as appropriate to make the sections as uniform as possible. These procedures improved the illustrations aesthetically while leaving their essential content unchanged. In addition, computer-based surface-reconstruction techniques made possible the beautiful three-dimensional images that appear in Chapter 4 and elsewhere in the book. John Nolte and Todd W. Vanderah

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AC K N OW L E D G M E N T S This book could never have happened without the hard work and endless efforts of Jack Nolte. He loved to teach and mentor colleagues of which I am forever indebted. Many colleagues and friends have helped with previous versions of the book, and that work is presented in this edition, including the photographic expertise of Nathan Nitzky and Jeb Zirato in the UofA Biocommunications. Grant Dahmer and Dr. Norman Koelling of the UofA prepared the prosections shown in Chapter 1. The sections shown in Chapter 2 were cut by Shelley Rowley, and those in Chapter 3 by Pam Eller. John Sundsten produced the three-dimensional images shown in Chapter 4. Paul Yakovlev, as detailed shortly, was the central figure in the production of the sections shown in Chapters 5 through 7. Cody Thorstenson played a major role in retouching the images of these sections. Cheryl Cotman produced the threedimensional reconstructions of the limbic system shown in Chapter 8. Drs. Ray Carmody, Robert Handy, Elena Plante, and Joe Seeger provided the images shown in Chapters 9 and 10. Drs. Agamanolis and Carmody supplied many of the pathology images in chapter 10 and helped with the description of the neuropathology. I thank the co-author on the first three editions of this atlas, Jay B. Angevine Jr., who passed away in October 2011. Dr. Angevine was responsible for producing the whole-brain sections in Chapters 5 through 7. Drs. Nolte and Angevine both had an infectious love for the central nervous system and its incredible capability. Their personalities and enthusiasm made learning about the nervous system fun

and exciting. I hope this enjoyment for the nervous system feeds forward to future students of the human nervous system. Todd W. Vanderah

Jay B. Angevine Jr. June 29, 1928–October 18, 2011.

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A NOTE ON THE WHOLE-BRAIN SERIAL SECTIONS AND THEIR ORIGIN As crucial as computer technology is to our book, the whole-brain serial sections are its foundation. They were prepared during 1966–1967 in the Warren Anatomical Museum at Harvard Medical School. The work, in which I took part, was performed under the direction of Dr. Paul I. Yakovlev (1894–1983), who was curator of the museum from 1955 to 1961 and then Emeritus Clinical Professor of Neuropathology until 1969. Each brain, embedded whole in celloidin, was sectioned in coronal, horizontal, or sagittal planes on a giant microtome with a standing oblique 36-inch blade and a sliding brain holder. The sections, each 35 µm thick, were rolled and stored in test tubes in a console of 100 numbered receptacles. After processing pilot sections for suitability and quality, we stained every twentieth section with Weigert’s hematoxylin (Loyez method) for myelin and mounted it between sheets of window glass. Each preparation is thus about 4 mm thick, yet great depth and detail of cells and fibers are visible. Such preparations illustrate the white matter and tracts of the brain by staining the myelin sheaths of axons black; gray matter and nuclei appear as more or less pale areas, depending on the number and caliber of myelinated fibers present. These sections, all from essentially normal brains, were added to an already huge collection representing more than 900 cerebra that Dr. Yakovlev had been building since 1930. Now a national resource known and available to neurological scholars worldwide, this priceless compilation known as the Yakovlev-Haleem Collection is graciously housed in the National Museum of Health and Medicine by the Armed Forces Institute of Pathology in Washington, DC. Today it comprises about 1600 specimens, normal and pathological, processed in a rigorously consistent manner from the start. In mid-1967, with Dr. Yakovlev’s blessing, I took with me to The University of Arizona some 1000 of the 8741 sections cut from the three normal brains used in Chapters 5 through 7 of this book. I had left Boston to join the faculty of the University’s new College of Medicine in Tucson. Paul, my mentor from the time I came to Harvard in 1956, wanted to support me as I began teaching in a far-off land that he believed (perhaps correctly) to be a frontier: the “Wild West.” As with everything else he did, it was thoughtful, kind, and generous. How he would have loved to see students studying the sections illustrated on these pages! Unlike the fairly simple task of sectioning the brainstem, cutting perfect gapless whole-brain serial sections is difficult. The procedure was never more carefully undertaken or widely employed than by Paul, who used it at or in association with Harvard Medical School for 40 years. A central theme for him was this holistic method (“every part of the brain is there, nothing is left out…”), but no aspect of neuroanatomy or neuropathology failed to intrigue him. Although such sections had been made since the late 19th century (they are found in small numbers at many medical schools and

in profusion at a few research institutes), Paul’s are unique—in uniformity of preparation at every step from fixation to mounting, and in unity of general neurological interest and comparability. Of this legacy (he called it “over 40 tons of glass”), Derek Denny-Brown, Emeritus Professor of Neurology at Harvard, wrote in 1972: “The perspective given by serial whole brain sections provides at once an arresting view of anatomical relationships in patterns of striking beauty. After working in the collection for years, one still finds every occasion to view it illuminating and rewarding.” In 2000, artist-scientist Cheryl Cotman, computer programmer Kevin Head, and I, an anatomist, traced and digitized structures from the serial sagittal sections shown in this atlas. We made a computer reconstruction and large hologram (three by five feet) of the human limbic system. We are indebted to Cheryl for her help in selecting images from her large collection of color-coded overall and regional views of the system. We are enlightened by her discovery that several limbic structures are quite differently shaped than traditionally believed. Although Paul and I would find this hard to accept, we would accept her fantastic findings with glee and laughter. -Jay B. Angevine Jr.

Paul I. Yakovlev, MD 1894–1983. An autographed copy of an oil portrait of Paul Yakovlev by Bettina Steinke. The original portrait was presented to the Warren Anatomical Museum at Harvard Medical School in 1978. (Courtesy the Warren Museum in the Francis A. Countway Library of Medicine, Boston, Massachusetts.)

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CONTENTS In Memoriam, v Preface, vii Acknowledgments, ix A Note on the Whole-Brain Serial Sections and Their Origin, xi 1 External Anatomy of the Brain, 1 2 Transverse Sections of the Spinal Cord, 23 3 Transverse Sections of the Brainstem, 31 4 Building a Brain: Three-Dimensional Reconstructions, 49 5 Coronal Sections, 53 6 Axial Sections, 79 7 Sagittal Sections, 103 8 Functional Systems, 125

Long Tracts of the Spinal Cord and Brainstem, 125 Sensory Systems of the Brainstem and Cerebrum, 125 Cranial Nerve Motor Nuclei, 125 Visceral Afferents and Efferents, 125

Basal Ganglia, 125 Cerebellum, 125 Thalamus and Cerebral Cortex, 125 Hypothalamus and Limbic System, 125 Chemically Coded Neuronal Systems, 125

9 Clinical Imaging, 187 10 An Introduction to Neuropathology, 215 Primary Brain Tumors, 215 Astrocytomas, 215 Infiltrating Astrocytomas, 217 Oligodendrogliomas, 220 Ependymomas, 221 Medulloblastomas, 222 Meningioma, 224 Detection of an Abscess, 226 Demyelinating Syndromes, 227 Neurodegenerative Diseases, 230

Glossary, 235 Index, 273

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1  External Anatomy of the Brain and hippocampus). They are apparent in the brain sections shown in Chapters 5 through 7. The cerebral hemispheres of humans are so massive that they overshadow or almost conceal the remaining major subdivisions of the brain—the diencephalon (made up of the thalamus, hypothalamus, epithalamus), brainstem, and cerebellum. Hemisecting a brain in the midsagittal plane, as in Fig. 1.1B, reveals these components. The diencephalon (literally the “in-between brain”) is interposed between each cerebral hemisphere and the brainstem. The diencephalon contains the left and right thalamus, major waystations for information seeking access to the cerebral cortex; the hypothalamus, a major control center for visceral and drive-related functions; and the epithalamus, which includes the pineal gland and a set of nuclei called the habenula. The brainstem, continuous caudally with the spinal cord, serves as a conduit for pathways traveling between the cerebellum or spinal cord and more rostral levels of the CNS. It also contains the neurons that receive or give rise to most of the cranial nerves. The cerebellum (literally the “little brain”) is even more intricately convoluted than the cerebral hemispheres, to make room for an extensive covering of its own cortex. It plays a major role in the planning and coordination of movement. A deep transverse fissure (normally occupied over most of its extent by the tentorium cerebelli) separates the cerebellum from the overlying occipital and parietal lobes and then continues deeper into the brain, partially separating the diencephalon from the cerebral hemispheres.

This atlas emphasizes views of the interior of the human central nervous system (CNS), sectioned in various planes. Here in the first chapter we lay some of the groundwork for understanding the arrangements of these interior structures by presenting the surface features with which they are continuous, and by giving a broad overview of the components of the CNS. The CNS is composed of the spinal cord and the brain, the major components of which are indicated in Fig. 1.1. The human brain is dominated by two very large cerebral hemispheres, separated from each other by a deep longitudinal fissure. Each hemisphere is convoluted externally in a fairly consistent pattern into a series of gyri, separated from each other by a series of sulci (an adaptation that makes more area available for the cortex that covers each cerebral hemisphere). Several prominent sulci are used as major landmarks to divide each hemisphere into five lobesa— frontal, parietal, occipital, temporal, and limbic—each of which contains a characteristic set of gyri (Figs. 1.3 to 1.8). The two hemispheres are interconnected by a massive bundle of nerve fibers, the corpus callosum, and two smaller bundles of fibers called the anterior and posterior commissures. Finally, certain areas of gray matter are embedded in the interior of each cerebral hemisphere. These include major components of the basal ganglia (or, more properly, basal nuclei) and limbic system (primarily the amygdala

a

In addition, the insula, an area of cerebral cortex buried deep in the lateral sulcus (see Fig. 5.7A), is usually considered as a separate lobe.

A

B

Central sulcus

Central sulcus

Corpus callosum

Frontal lobe Parietal lobe

Frontal lobe

Limbic lobe

Occipital lobe

Temporal lobe

Parietooccipital sulcus Parietal lobe

Ce

reb

Limbic lobe

Lateral sulcus

Cerebellum Brainstem

Occipital lobe

Temporal lobe

ell

um

Cerebellum Transverse fissure

Diencephalon Brainstem

Figure 1.1  Lateral and medial surfaces of the brain. (A) The left lateral surface of the brain; anterior is to the left. (B) The medial surface of the right half of the sagittally hemisected brain; anterior is to the left. (Dissections by Grant Dahmer, Department of Cell Biology and Anatomy, The University of Arizona College of Medicine.)

1

2

Nolte’s The Human Brain in Photographs and Diagrams

A

Longitudinal fissure

Basilar artery

Olfactory bulb & tract

Anterior spinal artery Accessory nerve (CN XI) Vertebral artery C1 ventral (anterior) root C2 ventral (anterior) root dorsal (posterior) root

Frontal lobe

Optic nerve (CN II) Hypoglossal nerve (CN XII) Internal carotid artery Temporal lobe

C1

Trigeminal nerve (CN V)

C2

Basilar artery

Cut edge of arachnoid

C3

Vertebral artery

Cut edge of dura

C4 C5 C6

C3 dorsal (posterior) root ventral (anterior) root

C7 C8

Ventral (anterior) roots:

T1

C2

T2 T3

Anterior spinal artery

T4

C3

T5 T6

Denticulate ligament

T7

C4

T8

Anterior spinal artery

T9

C5

T10 T11

C6

Anterior spinal artery

T12

L1

C8: ventral (anterior) root dorsal (posterior) root

L2

T1: ventral (anterior) root dorsal (posterior) root

L3 L4 L5

T2: ventral (anterior) root dorsal (posterior) root

S1 S2 S3 S4

Denticulate ligament T3

Sacrum

T4 Figure 1.2  A masterful dissection of the entire CNS, with the spinal cord still encased in dura mater and arachnoid. (A) The anterior/inferior surface. Regions enlarged in the insets, after the dura mater and arachnoid were spread apart.

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CHAPTER 1  External Anatomy of the Brain

B

Longitudinal fissure Parietal lobe Occipital lobe

T11

Temporal lobe Cerebellum: vermis hemisphere

T12

C1

Posterior inferior cerebellar branches

C2 C3

Vertebral artery

Conus medullaris

C4

Cut edge of dura & arachnoid

C5 C6

Cut edge of arachnoid

C7

Cut edge of dura

C8 T1

Filum terminale

T2

(pial part)

T3

Cauda equina

T4 T5

Cauda equina

T6 T7

L5

T8 T9

L5

Filum terminale (pial part)

T10 T11

S1 T12

S1 L1

L2 L3

S3 Filum terminale (dural part)

L4

S2

S2

L5

S3 S4

S1

S4 Coccygeal

S2

S5

S3 S4 S5

Filum terminale (dural part)

Sacrum S5 Coccygeal

Coccygeal

Figure 1.2 (Continued) (B) The posterior surface of the entire CNS. The cauda equina and the caudal end of the spinal cord, enlarged in the insets after the dura mater and arachnoid were spread apart. (Dissection by Dr. Norman Koelling, Department of Cell Biology and Anatomy, The University of Arizona College of Medicine.)

4

Nolte’s The Human Brain in Photographs and Diagrams

A

B

C

D

F

E

G

Figure 1.3  Multiple views of a brain. Only major structures are labeled here. (A) The right lateral surface (anterior toward the right). (B) The left lateral surface (anterior toward the left). (C) The anterior surface. (D) The superior surface (anterior toward the top of the page). (E) The posterior surface. (F) The inferior surface (anterior toward the top of the page). (G) The same inferior surface after removal of the cerebellum and most of the brainstem; the latter are shown in more detail in Fig. 1.9.

5

CHAPTER 1  External Anatomy of the Brain Superior parietal lobule

Central sulcus

Superior parietal lobule

Central sulcus

Intraparietal sulcus

IPL

Po Pr

Pr

MFG

MFG

IFG Occ

Intraparietal sulcus Po

IPL

IFG Temp

Temp

Occ

Lateral sulcus Cerebellum:

Brainstem

Cerebellum:

hemisphere

hemisphere

Inferior frontal gyrus

Longitudinal fissure

Longitudinal fissure

SPL

Central sulcus

MFG SFG

MFG SFG

Intraparietal sulcus

IPL

IFG

Occ

Po

Temp

Pr

Temp Lateral sulcus Cerebellum: hemisphere

SPL Brainstem

Orbital gyri Brainstem

Occ Intraparietal sulcus

Inferior parietal lobule

Cerebellum: vermis hemisphere

Longitudinal fissure Orbital gyri

Optic chiasm

Olfactory bulb & tract

Rhinal sulcus

Infundibulum

Uncus

Midbrain

Parahippocampal gyrus

Temp

Collateral sulcus

Pons

Occipitotemporal gyrus

Cerebellum: flocculus hemisphere vermis

Thalamus Occ

Occ

Medulla Corpus callosum

Longitudinal fissure

Figure 1.3 (Continued) (The rhinal sulcus is drawn as a dashed line to indicate that it is separate from the collateral sulcus, even though in this particular brain the two are continuous.) IFG, Inferior frontal gyrus; IPL, inferior parietal lobule; MFG, middle frontal gyrus; Occ, occipital lobe; Po, postcentral gyrus; Pr, precentral gyrus; SFG, superior frontal gyrus; SPL, superior parietal lobule; Temp, temporal lobe. (Dissection by Grant Dahmer, Department of Cell Biology and Anatomy, The University of Arizona College of Medicine.)

6

Nolte’s The Human Brain in Photographs and Diagrams Figure 1.4  Lateral and superior surfaces of the cerebral hemispheres. The arachnoid was not removed from this specimen, but major gyri and sulci are still apparent. (A) Lateral view of the left hemisphere. Numerous branches of the left middle cerebral artery can be seen emerging from the lateral sulcus and spreading over the lateral surface of the hemisphere beneath the arachnoid. (B) The same hemisphere as in (A), seen from a more anterior and superior vantage point. Anterior and posterior cerebral branches can be seen emerging from the longitudinal fissure and extending for a short distance over the superior surface of the hemisphere beneath the arachnoid. (Middle cerebral branches, although visible in this view, are not indicated.)

A

B

Precentral gyrus

Frontal gyri: superior middle inferior

Central sulcus

Postcentral gyrus

Supramarginal gyrus Superior parietal lobule Intraparietal sulcus

2

Angular gyrus

3

Occipital lobe

1 Transverse fissure Orbital gyri

Cerebellum (hemisphere)

Lateral sulcus Temporal gyri: superior middle inferior

Inferior frontal gyrus: 1. orbital part 2. triangular part 3. opercular part

Preoccipital notch

Supramarginal gyrus Postcentral gyrus

Cerebellum (flocculus)

Central sulcus

Superior parietal lobule

Arachnoid granulations Intraparietal sulcus Posterior cerebral branches

Longitudinal fissure Anterior cerebral branches

Precentral gyrus Frontal gyri: superior middle inferior

Angular gyrus Temporal gyri: superior middle

7

CHAPTER 1  External Anatomy of the Brain

Figure 1.4 (Continued) (C) Lateral view of the right hemisphere of the same brain shown in (A) and (B). Numerous branches of the right middle cerebral artery can be seen emerging from the lateral sulcus and spreading over the lateral surface of the hemisphere beneath the arachnoid, and a few posterior cerebral branches emerge from the longitudinal fissure. Although the two cerebral hemispheres of human brains are approximately mirror images of each other, some slight asymmetries are common, particularly in certain language-related areas. Note in this specimen how much farther posteriorly the lateral sulcus extends in the left hemisphere (A), and how much larger the triangular part of the inferior frontal gyrus is on the left (see also Fig. 1.5). (D) The same hemisphere as in (C) seen from a more anterior and superior vantage point. Anterior and middle cerebral branches can be seen emerging from the longitudinal fissure and extending for a short distance over the superior surface of the hemisphere beneath the arachnoid. (Middle cerebral branches, although visible in this view, are not indicated.) (Dissection by Grant Dahmer, Department of Cell Biology and Anatomy, The University of Arizona College of Medicine.)

C D

Postcentral Superior Intraparietal parietal Supramarginal gyrus sulcus lobule gyrus Central Angular sulcus Precentral gyrus gyrus Longitudinal fissure Frontal gyri: 3 Occipital lobe Posterior cerebral branches

2 1

Orbital gyri Lateral sulcus

Cerebellum (hemisphere)

Supramarginal gyrus

Temporal gyri: Cerebellum

Transverse fissure

superior middle inferior

(flocculus)

Preoccipital notch

Intraparietal sulcus

superior middle inferior

Posterior cerebral branch

Inferior frontal gyrus: 1. orbital part 2. triangular part 3. opercular part

Arachnoid granulations Superior parietal lobule Angular gyrus Temporal gyri: superior middle inferior

Postcentral gyrus

Precentral gyrus Central Longitudinal sulcus fissure Frontal gyri: superior middle inferior

Anterior cerebral branch

8

Nolte’s The Human Brain in Photographs and Diagrams Figure 1.5  (A and B) The left and right cerebral hemispheres of the brain. Note in this specimen how much farther posteriorly the lateral sulcus extends in the left hemisphere (A), and how much larger the triangular and opercular parts of the inferior frontal gyrus are on the left. (A) Lateral view of the left hemisphere. (B) Lateral view of the right hemisphere.

A

B

Frontal gyri:

Precentral gyrus

Central sulcus

superior middle inferior

Postcentral gyrus Supramarginal gyrus Superior parietal lobule Intraparietal sulcus

3 Angular gyrus

2 1

2 Occipital gyri

Orbital gyri Olfactory bulb

Lateral sulcus Temporal gyri:

Inferior frontal gyrus: 1. orbital part 2. triangular part 3. opercular part

superior middle inferior

Postcentral gyrus Central

Preoccipital notch

Supramarginal gyrus

sulcus

Precentral gyrus

Frontal gyri: superior middle inferior

Superior parietal lobule

Lateral sulcus

Intraparietal sulcus 3

Angular gyrus

2 1

Occipital gyri

Preoccipital notch

Orbital gyri Temporal gyri: superior middle inferior

Inferior frontal gyrus: 1. orbital part 2. triangular part 3. opercular part

9

CHAPTER 1  External Anatomy of the Brain

Figure 1.5 (Continued) (C and D) Lateral and superior surfaces of the left cerebral hemisphere shown in (A). (C) The same hemisphere as in (A), seen from a more anterior and superior vantage point. (D) The same hemisphere as in (A), seen from a more posterior and superior vantage point. (Dissection by Grant Dahmer, Department of Cell Biology and Anatomy, The University of Arizona College of Medicine.)

C

D

Central sulcus

Precentral gyrus

Postcentral Supramarginal gyrus gyrus Superior parietal lobule

Frontal gyri:

Intraparietal sulcus

superior middle inferior

Angular gyrus Occipital lobe

3 2

Preoccipital notch

2 1 Inferior frontal gyrus: 1. orbital part 2. triangular part 3. opercular part

Temporal gyri:

Precentral gyrus Central sulcus

Lateral sulcus

superior middle inferior

Postcentral gyrus Supramarginal gyrus Superior parietal lobule

Frontal gyri: superior middle inferior

1

2

Intraparietal sulcus

3

Angular gyrus

Inferior frontal gyrus: 1. orbital part 2. triangular part 3. opercular part

Occipital gyri

Lateral sulcus Temporal gyri: superior middle inferior

Preoccipital notch

10

Nolte’s The Human Brain in Photographs and Diagrams

Figure 1.6  (A) Inferior surface of the human brain.

A Longitudinal fissure Olfactory: sulcus bulb tract

Gyrus rectus Orbital gyri Uncus

Rhinal sulcus

Temporal gyri: superior middle inferior

Parahippocampal gyrus

Occipitotemporal (fusiform)

gyrus Transverse fissure Medulla Pons Cerebellum (hemisphere)

11

CHAPTER 1  External Anatomy of the Brain

Figure 1.6 (Continued) (B) The brainstem and the base of the forebrain at a closer view. (The large left posterior communicating artery is a common variant of the circle of Willis.) (Dissection by Grant Dahmer, Department of Cell Biology and Anatomy, The University of Arizona College of Medicine.)

B Anterior cerebral artery Medial striate artery Optic: nerve (CN II) chiasm tract

Anterior choroidal artery

Olfactory branch (medial striate artery)

Internal carotid artery Infundibulum Median eminence Tuber cinereum

Oculomotor nerve (CN III) Posterior cerebral artery Basilar artery Trigeminal nerve (CN V): motor root sensory root

Facial nerve (CN VII) Vestibulocochlear nerve (CN VIII) Cerebellum (flocculus)

Choroid plexus (in lateral aperture)

Posterior inferior cerebellar artery

Middle cerebral artery Posterior communicating artery Superior cerebellar artery Trochlear nerve (CN IV) Abducens nerve (CN VI) Anterior inferior cerebellar artery Glossopharyngeal nerve (CN IX) Vagus nerve (CN X) Hypoglossal nerve (CN XII)

Anterior spinal artery Vertebral artery

Cervical ventral root (C1)

12

Nolte’s The Human Brain in Photographs and Diagrams

A

Superior frontal gyrus Cingulate Anterior commissure gyrus Cingulate sulcus Corpus callosum:

Corpus callosum (body) Septum pellucidum

Central sulcus

Cingulate sulcus

Pineal gland

(marginal branch)

Subparietal sulcus Corpus callosum

rostrum genu

(splenium)

Parietooccipital sulcus Calcarine sulcus Thalamus Midbrain

Anterior cerebral artery

Pons

Subcallosal gyrus Hypothalamic sulcus Hypothalamus Uncus

Medulla

Rhinal sulcus Occipitotemporal gyrus

Inferior temporal gyrus

Cerebellum: primary fissure vermis hemisphere

Figure 1.7  (A) Medial surface of the right half of a sagittally hemisected brain. The dashed line interconnecting the cingulate and subparietal sulci is meant to indicate that in some brains these two sulci are continuous.

13

CHAPTER 1  External Anatomy of the Brain

B Septum pellucidum

Choroid plexus

Fornix (body)

Interthalamic Roof of the adhesion third ventricle

Internal cerebral vein

Third ventricle Habenula (suprapineal recess) Great vein

Septal vein

(of Galen)

Interventricular foramen

Pineal gland

Anterior commissure

Posterior commissure

Paraterminal gyrus Superior colliculus

Lamina terminalis Fornix (column)

Inferior colliculus

Anterior communicating artery

Aqueduct Superior cerebellar peduncles (decussation)

Third ventricle (optic recess)

Optic nerve (CN II)

Fourth ventricle

Optic chiasm

Choroid plexus

Third ventricle (infundibular recess)

Infundibulum Mammillary body

Oculomotor nerve (CN III)

Cerebral peduncle

Basal pons

Pons (tegmentum)

Figure 1.7 (Continued) (B) The diencephalon and part of the brainstem. (Dissection by Grant Dahmer, Department of Cell Biology and Anatomy, The University of Arizona College of Medicine.)

14

Nolte’s The Human Brain in Photographs and Diagrams Figure 1.8  Additional views of the cerebral hemispheres of the brain. (A) Medial view of the left hemisphere. In this brain, unlike the one in Fig. 1.7, the cingulate and subparietal sulci are continuous with one another. (B) The same left hemisphere as in (A), seen from a more inferior vantage point.

A

Paracentral lobule Central sulcus

B Stria medullaris of the thalamus

Cingulate sulcus

Corpus callosum

(marginal branch)

Cingulate gyrus

Subparietal sulcus

Superior frontal gyrus

Precuneus

Cingulate sulcus

Cingulate gyrus (isthmus)

Fornix Anterior commissure

Parietooccipital sulcus

Gyrus rectus

Cuneus Calcarine sulcus

Uncus

Occipitotemporal Lingual Collateral (fusiform) sulcus Parahippocampal gyrus Inferior gyrus gyrus temporal gyrus

Olfactory bulb

Paracentral lobule Corpus callosum

Stria medullaris of the thalamus Cingulate gyrus Fornix

Central sulcus

Choroid plexus

Cingulate sulcus

Superior frontal gyrus

(marginal branch)

Precuneus

Cingulate sulcus

Subparietal sulcus Parietooccipital sulcus

Anterior commissure

Cuneus

Gyrus rectus

Calcarine sulcus

Olfactory bulb

Lingual gyrus

Olfactory tract

Cingulate gyrus (isthmus)

Orbital gyri

Collateral sulcus Inferior temporal gyrus Occipitotemporal (fusiform) gyrus

Substantia nigra Uncus Parahippocampal gyrus

15

CHAPTER 1  External Anatomy of the Brain

Figure 1.8 (Continued) (C) Prying open the lateral sulcus of the right hemisphere shown in Fig. 1.5B reveals the insula. (D) Cutting away the frontal, parietal, and temporal opercula also reveals the insula. (Dissection by Grant Dahmer, Department of Cell Biology and Anatomy, The University of Arizona College of Medicine.)

C

D

Central sulcus Postcentral gyrus

Frontal gyri: Precentral gyrus

superior middle inferior

Supramarginal gyrus Angular gyrus

2 3

1 Orbital gyri

Occipital gyri

Transverse temporal gyri (of Heschl)

Insula (long gyri)

Insula (short gyri)

Inferior frontal gyrus: 1. orbital part 2. triangular part 3. opercular part

Postcentral gyrus Central Precentral sulcus gyrus

Frontal gyri: superior middle inferior

Supramarginal gyrus Angular gyrus

Occipital gyri Limen insulae

Temporal gyri: superior middle inferior

Insula (long gyri)

Insula (short gyri)

Orbital gyri

16

Nolte’s The Human Brain in Photographs and Diagrams

2b

2a

A

Aqueduct

Inferior & Superior colliculi

Red nucleus Substantia nigra Cerebral peduncle

Superior colliculus

CN III

CN IV

CN VIII & VII 3a

Basal pons 5a 1

Pyramid 3b

5b

4b

4a

Basal pons CN III Figure 1.9  (A) The cerebellum from the same brain as in Fig. 1.3. Views of the superior (2), posterior (3), inferior (4), and anterior (5) surfaces are shown, both before and after the brainstem was removed.

CHAPTER 1  External Anatomy of the Brain

17

Posterior lobe (vermis)

Horizontal fissure 2

B

Posterior lobe (hemisphere)

Anterior lobe

Anterior lobe

(vermis)

(hemisphere)

Anterior lobe

Primary fissure

(hemisphere)

5

(vermis)

S

S M Posterior lobe (hemisphere)

Anterior lobe

M

Anterior lobe

I

(vermis)

I

Primary fissure 1

Flocculus

Posterior lobe (vermis)

Anterior lobe Tonsil

(hemisphere)

M

S

Horizontal fissure

e lob ir or ere)

I

Posterior lobe

ste ph Po emis

(vermis)

(h

4 Posterior lobe (hemisphere)

Tonsil

Posterior lobe (vermis)

Anterior lobe (vermis)

Anterior lobe (hemisphere)

Tonsil Flocculus

Primary fissure Posterior lobe (vermis)

Posterior lobe (hemisphere)

Posterior lobe

3

(hemisphere)

Horizontal fissure

Tonsil

Figure 1.9 (Continued) (B) Major structures of the same cerebellum. I, M, and S indicate the inferior, middle, and superior cerebellar peduncles, respectively. (Dissection by Grant Dahmer, Department of Cell Biology and Anatomy, The University of Arizona College of Medicine.)

18

A

Nolte’s The Human Brain in Photographs and Diagrams Longitudinal fissure Olfactory:

Gyrus rectus

sulcus bulb tract

Orbital gyri

Uncus Temporal gyri: superior middle inferior

Transverse fissure

Cerebellum (hemisphere)

Pons

B

Vestibulocochlear nerve (CN VIII)

Medulla

Choroid plexus (in lateral aperture)

Abducens nerves (CN VI)

Cerebellum (flocculus)

Facial nerve (CN VII): sensory root (intermediate nerve) motor root

Glossopharyngeal nerve (CN IX)

Olive

Vagus nerve (CN X) Accessory nerve (CN XI) Pyramid Denticulate ligament Hypoglossal nerve (CN XII)

Cervical dorsal root (C2)

Pyramidal decussation Cervical ventral roots: C1 C2

Figure 1.10  Inferior and lateral views of the cerebrum and brainstem, demonstrating the cranial nerves. (A) Inferior view. (B) Lateral and inferior view.

CHAPTER 1  External Anatomy of the Brain

C Optic: chiasm nerve tract

Median eminence

Mammillary body

Tuber cinereum

Cerebral peduncle

Oculomotor nerve (CN III)

Trigeminal nerve (CN V):

Trochlear nerve (CN IV)

motor root sensory root

Abducens nerve (CN VI)

Facial nerve (CN VII): sensory root (intermediate nerve) motor root

Vestibulocochlear nerve (CN VIII) Glossopharyngeal nerve (CN IX)

* *

Cerebellum (flocculus)

*

*Olive

Choroid plexus (in lateral aperture)

Hypoglossal nerve (CN XII)

Vagus nerve (CN X)

Pyramid

Accessory nerve (CN XI) Denticulate ligament

Infundibulum

Pyramidal decussation Cervical ventral roots:

Cervical dorsal root (C2)

C1 C2

Figure 1.10 (Continued) (C) Inferior view. (Dissection by Dr. Norman Koelling, Department of Cell Biology and Anatomy, The University of Arizona College of Medicine.)

19

20

Nolte’s The Human Brain in Photographs and Diagrams

Habenula

A

Third ventricle

Pulvinar

Pineal gland

Medial geniculate nucleus Brachium of the inferior colliculus

Brachium of the superior colliculus Superior colliculus

Inferior colliculus

Trochlear nerve (CN IV)

Cerebellum (lingula)

Facial colliculus

Cerebellar peduncles:

Sulcus limitans

superior middle inferior

Hypoglossal trigone Vagal trigone Area postrema

Vagus nerve (CN X)

Obex

Accessory nerve (CN XI)

Fasciculus cuneatus

Cuneate tubercle

Fasciculus gracilis

Gracile tubercle Cervical dorsal root (C2)

Optic tract

Infundibulum

Mammillary body

B Oculomotor nerve (CN III)

Cerebral peduncle Trochlear nerve (CN IV)

Trigeminal nerve (CN V): motor root sensory root

Pons

Abducens nerve (CN VI)

Cerebellum

Facial nerve (CN VII)

(flocculus)

Vestibulocochlear nerve (CN VIII)

Glossopharyngeal nerve (CN IX)

* *

Vagus nerve (CN X) Accessory nerve (CN XI)

*Olive Hypoglossal nerve (CN XII) Pyramid

Cervical ventral roots: C1 C2

Pyramidal decussation

Figure 1.11  Four views of a brainstem. (A) The dorsal surface, looking down on the floor of the fourth ventricle. (B) The ventral surface.

CHAPTER 1  External Anatomy of the Brain

C

Superior colliculus Lateral lemniscus Cerebellar peduncles: Accessory nerve (CN XI)

Cerebellum

Medial geniculate nucleus

Pineal gland

Inferior colliculus & its brachium

superior middle inferior

Pulvinar

(flocculus)

Cervical dorsal root (C2) Cervical ventral roots: C2 C1

*

Vagus nerve (CN X) Hypoglossal nerve (CN XII)

*

Pons

Pons

*Olive

Vestibulocochlear nerve (CN VIII) Facial nerve (CN VII)

Cerebral peduncle

Mammillary bodies

Trigeminal nerve (CN V)

Oculomotor Trochlear nerve (CN III) nerve (CN IV)

Abducens nerve (CN VI)

D

Cervical dorsal root (C2) Cerebellar peduncles:

Inferior colliculus Pulvinar

Lateral lemniscus

Pineal gland

superior middle inferior

Accessory nerve (CN XI)

Superior colliculus Brachium of the superior colliculus Brachium of the inferior colliculus Pons

Cerebral peduncle

Olive

Trochlear nerve (CN IV)

Cervical ventral root (C1)

Vagus nerve (CN X) Oculomotor nerve (CN III) Trigeminal nerve (CN V)

Facial nerve (CN VII)

Vestibulocochlear nerve (CN VIII)

Figure 1.11 (Continued) (C) Right side. (D) Left side. (Dissection by Grant Dahmer, Department of Cell Biology and Anatomy, The University of Arizona College of Medicine.)

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2  Transverse Sections of the Spinal Cord The spinal cord is perhaps the most simply arranged part of the central nervous system (CNS). Its basic structure, indicated in a schematic drawing of the eighth cervical segment (Fig. 2.1), is the same at every level—a butterfly-shaped core of gray matter surrounded by white matter. An often indistinct central canal in the middle of the butterfly is the remnant of the lumen of the embryonic neural tube. The extensions of the gray matter posteriorly and anteriorly are termed the posterior and anterior (dorsal and ventral) horns, respectively. The zone where the two horns meet is the intermediate gray. At every level, the posterior horn is capped by a zone of closely packed small neurons, the substantia gelatinosa. Beyond this, there are level-to-level variations in the configuration of the spinal gray (Fig. 2.2). For example, the motor neurons that innervate skeletal muscle are located in the anterior horns, so these horns expand laterally in lumbar and lower cervical segments to accommodate the many motor neurons required for the muscles of the lower and upper extremities. Other examples are pointed out in Fig. 2.2. When studied in microscopic detail, the spinal gray matter can be partitioned into a series of 10 layers (Rexed laminae), as indicated on the right side of Fig. 2.1. Some of these laminae have clear functional significance. For example, lamina II corresponds to the substantia gelatinosa, which plays an important role in regulating sensations of pain and temperature. Spinal white matter contains pathways ascending to or descending from higher levels of the nervous system, as well as nerve fibers interconnecting different levels of the spinal cord. The horns of the gray matter serve to divide the white matter into posterior, lateral, and anterior funiculi. In contrast to the level-to-level

variations in the gray matter, the total amount of white matter increases steadily at progressively higher spinal levels (i.e., more white matter in the cervical area vs the sacral area). Moving rostrally, the ascending pathways enlarge as progressively more fibers are added to the funiculi; as fibers descend, they begin to stop at their corresponding levels of the spinal cord hence resulting in fewer fibers as they move caudally. Information travels to and from the spinal gray matter in the dorsal and ventral roots. The dorsal roots convey the central processes of afferents with cell bodies in dorsal root ganglia. As the roots approach the spinal cord, they break up into rootlets, each of which sorts itself into a medial division, containing the large-diameter afferents, and a lateral division, containing the small-diameter afferents. This is the beginning of two great streams of somatosensory information that travel rostrally in the CNS. The large fibers, primarily carrying information about touch and position, send branches into multiple levels of the gray matter and may send a branch rostrally in the ipsilateral posterior funiculus (or posterior column). The small fibers, primarily carrying information about pain and temperature, traverse a distinctive area of the white matter (Lissauer’s tract) and end more superficially in the gray matter of the posterior horn. Subsequent connections of both classes of afferents are reviewed in Chapter 8. In the pages that follow (as in all chapters in this atlas), only the largest and best-known spinal structures and pathways are indicated. Many others are either known to exist in humans or inferred from animal studies. In many cases, however, their functional significance is not well understood.

Large fibers Posterior (dorsal)

Small fibers

Dorsal rootlet

Posterior funiculus

Lissauer’s tract

III IV V VI

Substantia gelatinosa Interneurons X

VII

II

I Lateral funiculus

IX

IX VIII Motor neurons Ventral root

Anterior funiculus Actual size

Figure 2.1  Schematic drawing of the spinal cord at the level of the eighth cervical segment. (Modified from Nolte J: The Human Brain, ed 6, Philadelphia, 2009, Elsevier.)

23

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Nolte’s The Human Brain in Photographs and Diagrams

Figure 2.2  (A–H) Cross sections of a spinal cord at eight different levels, all shown at about the same magnification.

1

2 3 4

(A) The fourth sacral segment (S4). Several features common to all spinal levels can be seen. The substantia gelatinosa (4) caps the posterior horn (5). Also, afferent fibers entering through dorsal rootlets (2) sort themselves into smalldiameter fibers that move laterally and enter Lissauer’s tract (3) and large-diameter fibers that enter more medially (1) at the edge of the posterior funiculus. (This sorting occurs at all spinal levels and can be seen in all of the sections in this series.) Little white matter is present in any of the funiculi because most fibers either have already left descending pathways or have not yet entered ascending pathways. The anterior spinal artery (6) is cut in cross section as it runs longitudinally near the anterior median fissure of the cord. Shown enlarged in Fig. 2.3.

5

6

(B) The fifth lumbar segment (L5). This segment is in the lumbar enlargement (which extends from about L2 to S3) and has anterior horns that are enlarged, primarily in their lateral portions (1), to accommodate motor neurons for leg and foot muscles. Motor neurons located more medially (2) in the anterior horn innervate more proximal muscles, in this case hip muscles.

1

2 D

1

A (C) The second lumbar segment (L2). The posterior funiculus (1) is larger because ascending fibers carrying touch and position information from the lower limb have been added. The lateral funiculus is also larger, reflecting increased numbers of descending fibers in the lateral corticospinal tract (2) and ascending fibers in the spinothalamic tract (4). This section is at the rostral end of the lumbar enlargement, so the anterior horn (5) no longer is enlarged laterally. Clarke’s nucleus (3), which extends from about T1 to L3 and contains the cells of origin of the posterior spinocerebellar tract, makes its appearance. The anterior white commissure (6), the principal route through which axons can cross the midline in the spinal cord, is present at this and all other spinal levels. Shown enlarged in Fig. 2.4.

2

3

4 6

5

1 (D) The tenth thoracic segment (T10). The posterior (1) and anterior (4) horns are slender, corresponding to the relative dearth of sensory information arriving at this level and the relatively small number of motor neurons needed. Sympathetic preganglionic neurons form a lateral horn (3) containing the intermediolateral cell column, a characteristic feature of thoracic segments. Clarke’s nucleus (2) is still apparent. Shown enlarged in Fig. 2.5.

2

3

4

CHAPTER 2  Transverse Sections of the Spinal Cord

25

Figure 2.2 (Continued) Cross sections of a spinal cord.

1 2 (E) The fifth thoracic segment (T5). The posterior (1) and anterior (4) horns are even more slender, reflecting the relative paucity of sensory information arriving from the trunk and the relatively small number of motor neurons required by trunk muscles. Clarke’s nucleus (2), though smaller, is still present, as is the lateral horn (3).

3

4

1

2

3

(F) The eighth cervical segment (C8), near the caudal end of the cervical enlargement (C5 to T1). The posterior funiculus is subdivided by a partial glial partition into fasciculus gracilis (1), conveying touch and position information from the lower limb, and fasciculus cuneatus (2), conveying touch and position information from the upper limb. The anterior horn is enlarged, primarily laterally (3), to accommodate motor neurons for hand and forearm muscles. Motor neurons in more medial parts of the anterior horn (4) innervate more proximal muscles, such as the triceps. Shown enlarged in Fig. 2.6.

H 4 E 2

3 4

1

(G) The fifth cervical segment (C5), still in the cervical enlargement. As in the previous section, the posterior funiculus is subdivided into fasciculus gracilis (1) and fasciculus cuneatus (2), and the anterior horn includes an expanded lateral region (3, here containing motor neurons for forearm muscles) and the more medial area (4) that is present at all spinal levels (and at this level innervates shoulder muscles).

1 (H) The third cervical segment (C3), rostral to the cervical enlargement. The posterior horn (1) is more slender, reflecting the smaller amount of afferent input arriving from the neck. The anterior horn (2) is no longer enlarged laterally. The area of white matter, however, is larger than in any other section in this series, reflecting the near-maximal size of both ascending and descending pathways. Shown enlarged in Fig. 2.7.

2

26

Nolte’s The Human Brain in Photographs and Diagrams

Actual size

Posterior column (fasciculus gracilis at this level)

Dorsal rootlet

Large fiber entry zone

Lissauer’s tract & small fiber entry zone

Central canal

Substantia gelatinosa

Large fiber entry zone Lateral corticospinal tract

Lissauer’s tract

Anterior horn motor neurons (for distal muscles)

Spinothalamic tract Substantia gelatinosa

Anterior horn motor neurons (for proximal muscles)

Anterior spinal artery

Ventral root fibers

Large fibers entering posterior horn

Motor neurons

Posterior spinal artery Ventral root fibers

Anterior spinal artery

Figure 2.3  Fourth sacral segment (S4). In this and the remaining figures in this chapter, the lower right inset indicates the areas supplied by the anterior and posterior spinal arteries.

CHAPTER 2  Transverse Sections of the Spinal Cord

Actual size

Posterior column (fasciculus gracilis at this level)

Lissauer’s tract & small fiber entry zone

Large fiber entry zone

Substantia gelatinosa

Posterior spinocerebellar tract

Lateral corticospinal tract Clarke’s nucleus

Anterior spinocerebellar tract Spinothalamic tract Large fiber entry zone Anterior horn motor neurons (for distal muscles)

Ventral root fibers

Central canal

Anterior horn motor neurons (for proximal muscles)

Lissauer’s tract Substantia gelatinosa Large fibers entering posterior horn Clarke’s nucleus Anterior white commissure Motor neurons

Posterior spinal artery Anterior spinal artery

Ventral root fibers Figure 2.4  Second lumbar segment (L2).

27

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Nolte’s The Human Brain in Photographs and Diagrams

Actual size

Posterior column (fasciculus (f i l gracilis at this level)

Large fiber entry zone

Dorsal rootlet

Lissauer’s tract & small fiber entry zone Substantia gelatinosa

Posterior spinocerebellar tract

Lateral corticospinal tract

Lateral horn Anterior spinocerebellar tract

Clarke’s nucleus

Spinothalamic tract Large fiber entry zone

Ventral root fibers

Central canal Anterior horn motor neurons Lissauer’s tract

Substantia gelatinosa Large fibers entering posterior horn Clarke’s nucleus Lateral horn (preganglionic sympathetic neurons)

Motor neurons

Posterior spinal artery Anterior spinal artery

Ventral root fibers Figure 2.5  Tenth thoracic segment (T10).

CHAPTER 2  Transverse Sections of the Spinal Cord

Actual size

Dorsal rootlet

Posterior column:

Large fiber entry zone

fasciculus gracilis

fasciculus cuneatus

Lissauer’s tract & small fiber entry zone

Substantia gelatinosa

Posterior spinocerebellar tract Lateral corticospinal tract Large fiber entry zone

Dorsal rootlet

Anterior spinocerebellar tract Spinothalamic tract Lissauer’s tract Substantia gelatinosa

Anterior corticospinal tract

Anterior horn motor neurons (for distal muscles)

Anterior horn motor neurons

Central canal

(for proximal muscles)

Ventral root fibers

Large fibers entering posterior horn

Motor neurons

Ventral root fibers

Figure 2.6  Eighth cervical segment (C8).

Posterior spinal artery Anterior spinal artery

29

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Nolte’s The Human Brain in Photographs and Diagrams

Actual size

Dorsal rootlet

Large fiber entry zone

Posterior column: fasciculus gracilis

fasciculus cuneatus

Substantia gelatinosa

Lissauer’s tract & small fiber entry zone

Accessory nerve fibers

Posterior spinocerebellar tract Lateral corticospinal tract Anterior spinocerebellar tract Large fiber entry zone Spinothalamic tract

Anterior horn motor neurons (accessory nucleus)

Central canal Anterior corticospinal tract Lissauer’s tract

Anterior horn motor neurons Anterior horn motor neurons (for proximal muscles)

(for distal muscles)

Ventral root fibers

Substantia gelatinosa Large fibers entering posterior horn

Accessory nerve fibers

Motor neurons

Posterior spinal artery Anterior spinal artery

Ventral root fibers

Figure 2.7  Third cervical segment (C3).

3  Transverse Sections of the Brainstem The brainstem contains the continuations of the long tracts seen in the spinal cord together with nuclei and tracts associated with cranial nerves and the cerebellum. These various tracts and nuclei surround, traverse, or are embedded in the reticular formation (named for its anatomical appearance—the Latin word reticulum means “network”), which forms a central core at all brainstem levels. This chapter considers the level-to-level arrangements of structures as seen in transverse sections of the brainstem; many of the same structures are revisited in Chapter 8 as parts of functional systems. The sections were made by Pam Eller and stained, as were the spinal cord sections in the previous chapter, by the Klüver-Barrera method, using luxol fast blue for myelin and a neutral red counterstain (which, despite its name, is a basic stain with an affinity for nucleic acids). The result is blue-violet staining of white matter and red staining of large neurons with prominent Nissl substance (e.g., hypoglossal motor neurons in Fig. 3.10) and of areas tightly packed with small neurons (e.g., the granular layer of cerebellar cortex in Fig. 3.10). A parasagittal section of the brainstem (Fig. 3.1) is used as a reference view throughout the chapter. It includes some of the features characteristic of each

brainstem level (Fig. 3.2), such as the superior and inferior colliculi of the midbrain, the basal pons, and a medullary pyramid. The three major longitudinal pathways (lateral corticospinal tract, posterior columns, and spinothalamic tract) that were followed through the spinal cord in Chapter 2 extend into the brainstem in consistent ways, as indicated in Fig. 3.3. Corticospinal fibers travel in the most ventral part of the brainstem, traversing the cerebral peduncle, basal pons, and medullary pyramid. At the spinomedullary junction, most of the fibers in each pyramid cross the midline (in the pyramidal decussation) and form the lateral corticospinal tract. Each posterior column terminates in the posterior column nuclei (nucleus gracilis and nucleus cuneatus) of the medulla. Afferent fibers from these nuclei decussate in the medulla to form the medial lemniscus, which travels rostrally and ends in the thalamus. The medial lemniscus starts out near the midline and then moves progressively more laterally as it proceeds rostrally through the brainstem (Fig. 3.4), rotating nearly 180 degrees in the process. The spinothalamic tract at all levels of the brainstem is at or near the lateral edge of the reticular formation. Cranial nerve nuclei are also arranged in reasonably consistent ways, as indicated schematically in Fig. 3.3 and in more detail in subsequent figures.

Superior colliculus

Thalamus

Inferior colliculus

Junction between diencephalon & brainstem Hypothalamus Basal pons Pyramid

Midbrain Pons

Fourth ventricle

Vi

Medulla

“Special” sensory (CN VIII)

STT

Reticular formation

B

ML

CST

a ud

l tra

l

ca

a ud

l

Figure 3.2  Levels of the brainstem.

A Sm

Ss

ca

s ro

Fasciculus gracilis

Figure 3.1  Parasagittal section of the brainstem and diencephalon.

Sp

al str ro al ud ca al s tr ro

Somatic sensory (mainly CN V)

Visceral sensory (CNs VII, IX, X) Autonomic (CNs III, VII, IX, X) Branchial motor (CNs V, VII, IX, X, XI)

Somatic motor (CNs III, IV, VI, XII)

Figure 3.3  Arrangement of cranial nerve nuclei in the rostral medulla. The left side of the figure indicates how visceral sensory (Vi), somatic sensory (Ss), and “special” sensory (Sp) (e.g., vestibular) nuclei are located lateral to the nuclei containing preganglionic autonomic neurons (A), somatic motor neurons (Sm), and motor neurons for muscles of branchial arch origin (B) (e.g., muscles of the larynx and pharynx). The cranial nerves containing each of these components are indicated on the right. (Not all of the nerves indicated actually emerge from the rostral medulla; they are included here for summary purposes.) CST, Corticospinal tract; ML, medial lemniscus; STT, spinothalamic tract.

31

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Nolte’s The Human Brain in Photographs and Diagrams

Corticospinal tract

Posterior column nuclei

Hy

Medial lemniscus

Reticular formation

C

Spinothalamic tract

Ves dV

Hy

Sol

Sol

spT Am spT dV

Am

(A) Caudal medulla (see Fig. 3.9).

(B) Rostral medulla (see Fig. 3.10).

Superior cerebellar peduncle

Ves Ab

Ves sT spT mT

Fa

Basal pons

(C) Caudal pons (see Fig. 3.12).

(D) Midpons (see Fig. 3.13).

Lateral lemniscus

EW Oc

Tr Decussation of the superior cerebellar peduncles DSCP

Cerebral peduncle (E) Caudal midbrain (see Fig. 3.15).

(F) Rostral midbrain (see Fig. 3.16).

Figure 3.4  Schematic views of six transverse sections of the brainstem, each enlarged about 3×, indicating major long tracts and cranial nerve nuclei. These are the same sections shown photographically in Figs. 3.9, 3.10, 3.12, 3.13, 3.15, and 3.16, and they correspond to planes of section indicated in Fig. 3.6. Abbreviations as in Fig. 3.6.

CHAPTER 3  Transverse Sections of the Brainstem

33

PCoA PCA SCA BA AICA (A) Caudal medulla (see Fig. 3.9).

(B) Rostral medulla (see Fig. 3.10).

PICA VA ASpA

Anterior spinal artery (ASpA)

Posterior spinal artery

Vertebral artery (VA)

Posterior inferior cerebellar artery (PICA)

Basilar artery (BA)

(C) Caudal pons (see Fig. 3.12).

(D) Rostral pons (see Fig. 3.14).

Anterior inferior cerebellar artery (AICA)

Superior cerebellar artery (SCA)

Posterior cerebral artery (PCA) Posterior communicating artery (PCoA)

(E) Caudal midbrain (see Fig. 3.15).

(F) Rostral midbrain (see Fig. 3.16).

Figure 3.5  Schematic views of six transverse sections of the brainstem, each enlarged about 3×, indicating areas of arterial supply. These are the same sections shown photographically in Figs. 3.9, 3.10, 3.12, and 3.14 through 3.16, and they correspond to planes of section indicated in Fig. 3.6. At each level, the brainstem supply is a series of wedge-shaped territories with anterolateral areas fed by midline arteries (e.g., vertebral, basilar) and posterolateral areas fed by circumferential branches (e.g., PICA, posterior cerebral).

34

Nolte’s The Human Brain in Photographs and Diagrams

SENSORY

MOTOR

Somatic Visceral “Special”

Branchial Visceral (autonomic) Somatic Fig. 3-7L, 3-17

III

III

Oc

EW

Figs. 3-4F, 3-5F, 3-7K, 3-16

MIDBRAIN

Fig. 3-7J IV

V

Figs. 3-4E, 3-5E, 3-7I, 3-15

Tr mes

V

VI

VII VIII

Ab

Figs. 3-4C, 3-5C, 3-7F, 3-12

Fa

VII

Ves

Ss

VII V

C

Is

IX IX

IX

MEDULLA

X

X

XII

Hy

Am

dV

Fig. 3-7E, 3-11 Fig. 3-4B, 3-5B, 3-7D, 3-10

Sol X

Figs. 3-4D, 3-5D, 3-7G, 3-13

sT

mT

V

PONS

Figs. 3-7H, 3-14

Fig. 3-7C spT Figs. 3-4A, 3-5A, 3-7B, 3-9 Fig. 3-7A, 3-8 Fig. 3-7A

CERVICAL SPINAL CORD

XI

Ac

Midline Figure 3.6  The longitudinal arrangement of functional types of cranial nerve nuclei in the brainstem. The cranial nerves involved with each type of function are indicated on the left side of the diagram, and the actual nuclei are indicated on the right side. The dark blue line on each side represents the sulcus limitans, which (ideally, at least) separates motor nuclei medial to it from sensory nuclei lateral to it. Abbreviations for nuclei on the right side: Ab, Abducens nucleus; Ac, accessory nucleus; Am, nucleus ambiguus; C, cochlear nuclei; dV, dorsal motor nucleus of the vagus; EW, Edinger-Westphal nucleus (a subdivision of the oculomotor nucleus); Fa, facial nucleus; Hy, hypoglossal nucleus; Is, inferior salivary nucleus; mes, mesencephalic nucleus of the trigeminal; mT, motor nucleus of the trigeminal; Oc, oculomotor nucleus; Sol, nucleus of the solitary tract; spT, spinal nucleus of the trigeminal; Ss, superior salivary nucleus; sT, main sensory nucleus of the trigeminal; Tr, trochlear nucleus; Ves, vestibular nuclei. All of these nuclei (except the salivary nuclei) are indicated in one or more of the cross sections along the right side of the figure. (Modified from Nieuwenhuys R, Voogd J, van Huijzen C: The human central nervous system: a synopsis and atlas, ed 3, New York, 1988, Springer-Verlag.)

CHAPTER 3  Transverse Sections of the Brainstem

35

Figure 3.7  (A–L) Cross sections of a brainstem at 13 different levels, all shown at about the same magnification.

1

2

2 3

3

8 4 5

4 5

6 9 10

6 7

7

1

2 3 4 5 6

9

(B) Caudal medulla. Fasciculus gracilis has ended in nucleus gracilis (1), and fasciculus cuneatus (2) ends in nucleus cuneatus (3). Efferents from these posterior column nuclei cross the midline as internal arcuate fibers (9) and form the medial lemniscus (8). The spinothalamic tract (6) is in its typical location in the lateral part of the reticular formation, and the corticospinal tract traverses the pyramids (7). Trigeminal primary afferent fibers descend through the spinal trigeminal tract (4) to termination sites in the spinal trigeminal nucleus (5). Shown enlarged in Fig. 3.9.

7

8

1

(A) Spinomedullary junction. Fasciculus cuneatus (3) proceeds rostrally toward nucleus cuneatus (8, not yet present in the section on the left), and fasciculus gracilis (1) begins to terminate in nucleus gracilis (2). In the more rostral section on the right, internal arcuate fibers (9) leave the posterior column nuclei to cross the midline and form the medial lemniscus. The spinal trigeminal tract (4), at this level containing trigeminal pain and temperature afferents, and the spinal trigeminal nucleus (5), where these afferents terminate, replace Lissauer’s tract and the posterior horn of the spinal cord. The spinothalamic tract (6) is located anterolaterally, much as it was in the spinal cord. Corticospinal fibers that descended through the internal capsule, cerebral peduncle, basal pons, and medullary pyramid (10) now cross the midline in the pyramidal decussation (7). The section on the right is shown enlarged in Fig. 3.8.

2

3 4 5 6

9

10

11

7

8

12

1 2 3

4

5

6 9

8

(C) Rostral medulla. The central canal of the spinal cord and caudal medulla has given way to the fourth ventricle; part of its roof can be seen (2). Structures associated with cranial nerves appear in the floor of the fourth ventricle, including the hypoglossal nucleus (1), vestibular nuclei (3), and the solitary tract (5) surrounded by its nucleus. Efferents from the inferior olivary nucleus (9) cross the midline (again, as internal arcuate fibers) and join the contralateral inferior cerebellar peduncle (4). The locations of the spinothalamic tract (6), medial lemniscus (8), and corticospinal tract (7) are unchanged.

7

(D) Rostral medulla. A plane (dashed line) descending from the sulcus limitans (12) separates cranial nerve nuclei into a more medial group of motor nuclei and a more lateral group of sensory nuclei. Motor nuclei at this level include the hypoglossal nucleus (3) and the dorsal motor nucleus of the vagus (1, adjacent to the sulcus limitans). More laterally are vestibular nuclei (4), the spinal trigeminal nucleus (10), and the solitary tract and its nucleus (11, adjacent to the sulcus limitans). The locations of the medial lemniscus (8), spinothalamic tract (6), and corticospinal tract (7, in the pyramid) are unchanged. The inferior cerebellar peduncle (5) is substantially larger because efferents from the contralateral inferior olivary nucleus (9) have accumulated in it. Choroid plexus (2) can be seen in the roof of the fourth ventricle. Shown enlarged in Fig. 3.10. Illustration continued on following page

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Figure 3.7 (Continued) Cross sections of a brainstem at 13 different levels, all shown at about the same magnification.

4

3

1

2

5

(E) Pontomedullary junction. The fourth ventricle extends laterally, leading off into the lateral recess (5); choroid plexus (4) is visible in the roof of the ventricle. Vestibular (3) and cochlear (1) nuclei occupy the ventricular floor. The inferior cerebellar peduncle (2) has reached maximum size and is about to enter the cerebellum. The positions of the spinothalamic tract (6), inferior olivary nucleus (7), medial lemniscus (9), and corticospinal tract (8) are unchanged. Shown enlarged in Fig. 3.11.

6 9

7 8 (F) Caudal pons. Now the floor of the fourth ventricle (12) is occupied by the abducens nucleus (11), together with facial nerve fibers that emerge from the facial nucleus (4), hook around the abducens nucleus as the genu of the facial nerve, and leave the brainstem as the root of the facial nerve (3). The spinothalamic tract (9) is still located laterally in the reticular formation. The medial lemniscus (8) begins to move laterally and is traversed by crossing auditory fibers (7) of the trapezoid body. The corticospinal tract (6) is somewhat dispersed in the basal pons, surrounded by pontine nuclei and their transversely oriented efferents (5), which cross the midline and form the middle cerebellar peduncle (10). Deep cerebellar nuclei (1) appear in the roof of the fourth ventricle, and the superior cerebellar peduncle (13) begins to form adjacent to them. The inferior cerebellar peduncle (2) enters the cerebellum. Shown enlarged in Fig. 3.12.

13 1

12 11 2

10 3

9 8

4 7 6

5

1

8

2

7 3

6

4 (G) Midpons, at the level of entry of the trigeminal nerve (6). Many trigeminal fibers end in the main sensory nucleus of the trigeminal (8) or arise in the trigeminal motor nucleus (7). The superior cerebellar peduncle (1), carrying most of the output of the cerebellum, begins to enter the brainstem. The spinothalamic tract (2) is still located laterally in the reticular formation, the medial lemniscus (3) continues to move laterally, and the corticospinal tract (5) is still dispersed in the basal pons (4). Shown enlarged in Fig. 3.13.

5

2 3 (H) Rostral pons, near the pons-midbrain junction. The fourth ventricle (1) narrows as it approaches the aqueduct. The superior cerebellar peduncle (2) moves deeper into the brainstem just before beginning to decussate. The medial lemniscus (5) is now a flattened band of fibers with the spinothalamic tract (4) laterally adjacent to it. The lateral lemniscus (3) conveys ascending auditory fibers to the midbrain. The corticospinal tract (8) is surrounded by pontine nuclei (7) and their transversely oriented efferents (6). The locus ceruleus (9) is a small collection of pigmented neurons that provide most of the noradrenergic innervation of the CNS (see Fig. 8.38). Shown enlarged in Fig. 3.14.

4 5 6 7 8

1

9

CHAPTER 3  Transverse Sections of the Brainstem 1

2

37

Figure 3.7 (Continued) Cross sections of a brainstem at 13 different levels, all shown at about the same magnification.

3 4

(I) Caudal midbrain. The lateral lemniscus (4) ends in the inferior colliculus (3). The spinothalamic tract (5) and medial lemniscus (7) form a continuous band of fibers. The massive decussation of the superior cerebellar peduncles (8) occupies the center of the reticular formation. The basal pons gives way to a cerebral peduncle (9) on each side. The tiny trochlear nucleus (6) appears. At all midbrain levels, the cerebral aqueduct (1) is surrounded by periaqueductal gray matter (2). Shown enlarged in Fig. 3.15.

5 6 7 8 9

1

2

(J) Mid-midbrain. Characteristic midbrain features such as the aqueduct (1) and periaqueductal gray (2) can be seen, but no colliculi are present. The brachium of the inferior colliculus (4), spinothalamic tract (5), medial lemniscus (6), and now-crossed superior cerebellar peduncle (7) are all on their way to the thalamus. The oculomotor nucleus (3), substantia nigra (8), and cerebral peduncle (9) appear—all harbingers of the rostral midbrain.

3 4 5 6 7 8 9

1

2

3 4 5 6

(K) Rostral midbrain. Now the superior colliculus (3) appears and the oculomotor nucleus (9) is fully formed. The auditory pathway continues in the brachium of the inferior colliculus (4). The positions and appearance of the cerebral aqueduct (1), periaqueductal gray (2), spinothalamic tract (5), medial lemniscus (6), and cerebral peduncle (7) are little changed. Cerebellar efferents that reached the midbrain in the superior cerebellar peduncle (10) now begin to pass through or around the red nucleus. The substantia nigra (8) is more prominent. Shown enlarged in Fig. 3.16.

7

8 10

9

1

2

3 4

12 5

11

6

10

9

7 8

(L) Rostral midbrain, near the level of the midbrain-diencephalon junction. The cerebral aqueduct (1), periaqueductal gray (2), spinothalamic tract (3), medial lemniscus (5), cerebral peduncle (6), and substantia nigra (7) are still evident. The brachium of the inferior colliculus (4) ends in the medial geniculate nucleus (11), the first thalamic nucleus to appear in this plane of section. Cerebellar efferents (9) pass through and around the red nucleus (8) on their way to the thalamus. The ventral tegmental area (10) is a medial collection of neurons that provide the dopaminergic innervation of frontal cortex and limbic structures (see Fig. 8.39). Afferents from some retinal ganglion cells and visual cortex traverse the brachium of the superior colliculus (12) on their way to the superior colliculus. Shown enlarged in Fig. 3.17.

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Nolte’s The Human Brain in Photographs and Diagrams

Actual size

Fasciculus gracilis Nucleus gracilis Fasciculus cuneatus

Central canal

Nucleus cuneatus

Spinal trigeminal tract & nucleus

Posterior spinocerebellar tract Anterolateral system (spinothalamic + other tracts)

Anterior spinocerebellar tract

Internal arcuate fibers (crossing to form the medial lemniscus)

Reticular formation Accessory nucleus Pyramid

Medial longitudinal fasciculus (MLF) Fasciculus cuneatus Pyramidal decussation Nucleus cuneatus Spinal trigeminal tract & nucleus

Figure 3.8  Caudal medulla, near the spinomedullary junction.

CHAPTER 3  Transverse Sections of the Brainstem

Actual size

Dorsal motor nucleus of the vagus Solitary tract & its nucleus

Dorsal longitudinal fasciculus

Nucleus gracilis Central canal

Nucleus cuneatus Fasciculus cuneatus Lateral cuneate nucleus

Hypoglossal nucleus Medial longitudinal fasciculus (MLF)

Posterior spinocerebellar tract

Spinal trigeminal tract & nucleus

Nucleus ambiguus Anterior spinocerebellar tract

Internal arcuate fibers (crossing to form the medial lemniscus)

Vagus nerve rootlet (CN X)

Hypoglossal nerve rootlets (CN XII)

Anterolateral system (spinothalamic + other tracts)

Reticular formation Inferior olivary nucleus Pyramid

(medial accessory nucleus)

Medial lemniscus

Lateral cuneate nucleus Posterior spinocerebellar tract Spinal trigeminal tract Dorsal motor nucleus of the vagus Dorsal longitudinal fasciculus Hypoglossal nucleus (caudal end) Internal arcuate fibers (crossing to form the medial lemniscus)

Figure 3.9  Caudal medulla.

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Nolte’s The Human Brain in Photographs and Diagrams Cerebellar cortex: molecular layer granular layer

PICA branches

Actual size Inferior cerebellar peduncle (includes posterior spinocerebellar tract)

Dorsal cochlear nucleus

Medial vestibular nucleus Inferior vestibular nucleus Posterior spinocerebellar tract Spinal trigeminal tract & nucleus Anterior spinocerebellar tract Anterolateral system (spinothalamic + other tracts)

Internal arcuate fibers

Glossopharyngeal nerve (CN IX)

(crossing from opposite inferior olivary nucleus to inferior cerebellar peduncle)

Nucleus ambiguus

Inferior olivary complex: dorsal accessory nucleus inferior olivary nucleus medial accessory nucleus

Hypoglossal nerve rootlets (CN XII)

Central tegmental tract Reticular formation Pyramid

Medial lemniscus

Dorsal cochlear nucleus Lateral cuneate nucleus

Choroid plexus Fourth ventricle Sulcus limitans Dorsal longitudinal fasciculus Hypoglossal nucleus Medial longitudinal fasciculus (MLF) Dorsal motor nucleus of the vagus Nucleus of the solitary tract Solitary tract Figure 3.10  Rostral medulla. PICA, Posterior inferior cerebellar artery.

CHAPTER 3  Transverse Sections of the Brainstem

Fourth ventricle

Lateral recess Cerebellar cortex: granular layer molecular layer

Actual size Dorsal cochlear nucleus

Vestibular nuclei: medial

Medial longitudinal fasciculus (MLF)

inferior

superior

Dorsal longitudinal fasciculus Inferior cerebellar peduncle (includes posterior spinocerebellar tract)

Spinal trigeminal nucleus & tract Glossopharyngeal nerve (CN IX) Ventral cochlear nucleus Anterior spinocerebellar tract Anterolateral system (spinothalamic + other tracts)

Internal arcuate fibers (crossing from opposite inferior olivary nucleus to inferior cerebellar peduncle)

Reticular formation

Central tegmental tract Choroid plexus

Inferior olivary nucleus

Pyramid Medial lemniscus

Dorsal cochlear nucleus

Solitary tract Nucleus of the solitary tract

Ventral cochlear nucleus Spinal trigeminal nucleus & tract

Figure 3.11  Pontomedullary junction.

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Deep cerebellar nuclei: dentate interposed fastigial

Dorsal longitudinal fasciculus

Superior cerebellar peduncle

Inferior cerebellar peduncle

Fourth ventricle Vestibular nuclei:: superior i lateral

Solitary tract & its nucleus Anterior spinocerebellar tract Middle cerebellar peduncle Actual size

Lateral lemniscus Trapezoid body (crossing auditory fibers) Transverse pontine (pontocerebellar) fibers Abducens nucleus Pontine nuclei

Corticospinal, corticobulbar, and corticopontine fibers

Reticular formation Abducens nerve fibers Central tegmental tract Spinal trigeminal tract & nucleus Facial nerve (CN VII) Facial nucleus Superior olivary nucleus Anterolateral system (spinothalamic + other tracts)

Medial lemniscus Figure 3.12  Caudal pons.

Facial nerve (internal genu)

Medial longitudinal fasciculus (MLF)

CHAPTER 3  Transverse Sections of the Brainstem

Actual size

Superior vestibular nucleus

Medial longitudinal fasciculus (MLF)

Dorsal longitudinal fasciculus

Fourth ventricle Anterior spinocerebellar tract Superior cerebellar peduncle Reticular formation Central tegmental tract Medial lemniscus Trapezoid body (crossing auditory fibers)

Cerebellar cortex: granular layer Purkinje cell layer molecular layer

Transverse pontine (pontocerebellar) fibers

Corticospinal, corticobulbar, and corticopontine fibers

Pontine nuclei Trigeminal: mesencephalic nucleus mesencephalic tract main sensory nucleus motor nucleus

Lateral lemniscus Superior olivary nucleus Anterolateral system (spinothalamic + other tracts)

Figure 3.13  Midpons.

Trigeminal nerve

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Actual size

Medial longitudinal fasciculus (MLF) Fourth ventricle Periventricular gray

Dorsal longitudinal fasciculus Superior cerebellar peduncle

Parabrachial nuclei

Central tegmental tract Lateral lemniscus Anterolateral system (spinothalamic + other tracts)

Medial lemniscus Reticular formation Pontine nuclei Corticospinal, corticobulbar, and corticopontine fibers

Trochlear nerve fibers Transverse pontine (pontocerebellar) fibers

Trochlear decussation

Basilar artery

Trigeminal mesencephalic nucleus & tract

Locus ceruleus Dorsal longitudinal fasciculus

Dorsal raphe nucleus

Figure 3.14  Rostral pons, near the pons-midbrain junction.

CHAPTER 3  Transverse Sections of the Brainstem

Actual size

Cerebral aqueduct Periaqueductal gray

Inferior colliculus Lateral lemniscus

Trochlear nerve (CN IV) Dorsal longitudinal fasciculus Anterolateral system (spinothalamic + other tracts)

Central tegmental tract

Medial lemniscus

Pontine nuclei

Trochlear nucleus

Cerebral peduncle Dorsal raphe nucleus Reticular formation Decussation of the superior cerebellar peduncles

Dorsal longitudinal fasciculus

Medial longitudinal fasciculus (MLF)

Figure 3.15  Caudal midbrain.

Trochlear nerve fibers

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Actual size

Cerebral aqueduct Superior colliculus Anterolateral system (spinothalamic + other tracts)

Periaqueductal gray

Medial lemniscus

Brachium of the inferior colliculus Dorsal longitudinal fasciculus Central tegmental tract Substantia nigra: compact part reticular part

Superior cerebellar peduncle (entering red nucleus)

Reticular formation Ventral tegmental area Cerebral peduncle

Edinger-Westphal nucleus Central tegmental tract Oculomotor nucleus

Medial longitudinal fasciculus (MLF)

Oculomotor nerve fibers Basilar artery (perforating branch)

Figure 3.16  Rostral midbrain.

CHAPTER 3  Transverse Sections of the Brainstem

Actual size

Anterolateral system

Superior colliculus

Cerebral aqueduct

Periaqueductal gray

(spinothalamic + other tracts)

Dorsal longitudinal fasciculus Brachium of the inferior colliculus

Brachium of the superior colliculus

Central tegmental tract

Medial geniculate nucleus

Substantia nigra: compact part reticular part

Red nucleus

Medial lemniscus

Cerebral peduncle Reticular formation Ventral tegmental area

Cerebellothalamic fibers Edinger-Westphal nucleus Oculomotor nucleus Medial longitudinal fasciculus (MLF)

Substantia nigra: compact part reticular part

Red nucleus Ventral tegmental area Cerebellothalamic fibers rs Figure 3.17  Rostral midbrain, near the midbrain-diencephalon junction.

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4  Building a Brain: Three-Dimensional Reconstructions The interior of the forebrain is occupied by a series of structures that fit neatly together in three-dimensional space. As a consequence of the embryological development of the brain, some cerebral structures (e.g., lateral ventricle, caudate nucleus) curve around in a great C-shaped arc (Fig. 4.1), whereas others are more centrally located. One of the greatest impediments to understanding the interrelationships of cerebral structures in three dimensions is the typical presentation of the nervous system in a series of twodimensional sections cut in various planes (as it is presented in much of this book).

Body Head

As a partial solution to this dilemma, this chapter presents an overview of the arrangement of cerebral structures in the form of a series of computer-generated reconstructions kindly provided by Dr. John W. Sundsten and his colleagues (Department of Biological Structure, University of Washington School of Medicine). The images were made by cutting serial sections of a single human brain, digitizing outlines of structures of interest, and using these outlines to reconstruct (by computer) individual structures or groups of structures. Beginning with the reconstruction of the brainstem, cerebellum, and diencephalon shown in Fig. 4.2, major structures of the cerebral hemispheres are added sequentially in Fig. 4.3. Similar three-dimensional reconstructions are used in Chapters 5 through 7 to indicate the planes of sections through the forebrain.

A

Thalamus

Thalamus

(lateral geniculate nucleus)

Tail

Fornix

Middle cerebellar peduncle

Hypothalamus

B

Infundibulum Midbrain Basal pons Anterior horn

Body

Hippocampus

Cerebellum (hemisphere)

Pyramid

Cerebellum (flocculus)

Olive Figure 4.2  Three-dimensional reconstruction of the brainstem, cerebellum, and diencephalon. In an intact brain, the hypothalamus is continuous anteriorly with the preoptic and septal areas; in this reconstruction, the hypothalamus is shown ending abruptly at its approximate border with these structures. The midbrain is configured with a flattened anterior surface because the cerebral peduncle is not yet present; it will be added in Fig. 4.3E.

C

Inferior horn Figure 4.1  Three examples of C-shaped cerebral structures: (A) the caudate nucleus, (B) hippocampus/fornix system, (C) and lateral ventricle.

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Figure 4.3  (A–H) Building a brain. Thalamus

(A) The reconstruction of the brainstem, cerebellum, and diencephalon shown in Fig. 4.2. CF, Cerebellar flocculus (a specialized part of each cerebellar hemisphere); CH, cerebellar hemisphere; Hy, hypothalamus; Mid, midbrain.

Hy Mid

Hy

CH

CH

Pons CF CH

F F

F Hy HC

(B) The hippocampus (HC) is a special cortical area folded into the medial part of the limbic lobe, adjacent to the inferior horn of the lateral ventricle. The fornix (F) is a major output pathway from the hippocampus. It curves around in a C-shaped course (the Latin word fornix means “arch”) and terminates primarily in the hypothalamus (Hy) and in the septal area anterior to it.

B P (C) The lateral ventricle is another C-shaped structure, curving from an anterior horn (A) in the frontal lobe, through a body (B), and into an inferior horn (In) in the temporal lobe. A posterior horn (P) extends backward into the occipital lobe. The body, posterior horn, and inferior horn meet in the atrium (At) of the lateral ventricle. The body and anterior horn have a concave lateral wall; in reality, parts of the caudate nucleus occupy this depression (see Fig. 4.3D). The third ventricle (3) extends anteriorly beyond the truncated hypothalamus; in an intact brain, this anterior extension would be bordered by the preoptic area. The anterior commissure (AC) contains fibers interconnecting the temporal lobes.

A

At In

AC 3

B H

T

(D) The caudate nucleus, yet another C-shaped structure, curves through the hemisphere adjacent to the lateral ventricle. Its enlarged head (H) and body (B) account for the indented lateral wall of the anterior horn and body of the ventricle (see Fig. 4.3C). The attenuated tail (T) of the caudate nucleus forms part of the wall of the inferior horn of the ventricle.

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CHAPTER 4  Building a Brain: Three-Dimensional Reconstructions Figure 4.3 (Continued) Building a brain.

CR (E) The internal capsule (IC) is a thick band of fibers that covers the lateral aspect of the head of the caudate nucleus and the thalamus. It contains the vast majority of the fibers interconnecting the cerebral cortex and subcortical sites. Above the internal capsule, these fibers fan out within the cerebral hemisphere as the corona radiata (CR). Many of the cortical efferent fibers in the internal capsule funnel down into the cerebral peduncle (CP). The internal capsule also has a concave lateral surface; in this case the lenticular nucleus occupies the depression (see Fig. 4.3F).

IC

CP

P (F) The lenticular nucleus, itself a combination of the putamen and the globus pallidus, occupies the depression in the internal capsule (see Fig. 4.3E). The putamen (P, the more lateral of the two) and the caudate nucleus (C) are actually continuous masses of gray matter. The area of continuity is called the nucleus accumbens (A). The amygdala (Am) is a collection of nuclei underlying the medial surface of the limbic lobe at the anterior end of the hippocampus.

C A

Am

Central sulcus

(G) The structures described thus far are enveloped in white matter, containing the billions of axons interconnecting different cortical areas or interconnecting the cortex and subcortical structures. This reconstruction shows the junction between the cerebral cortex and its underlying white matter.

Lateral sulcus Po

SFG

Pr

SMG

MFG Po

Pr IFG

STG

(H) Finally, a thin (1.5 to 4.5 mm) layer of cerebral cortex covers each hemisphere. IFG, Inferior frontal gyrus; ITG, inferior temporal gyrus; MFG, middle frontal gyrus; MTG, middle temporal gyrus; Orb, orbital gyri; Po, postcentral gyrus; Pr, precentral gyrus; SFG, superior frontal gyrus; SMG, supramarginal gyrus; STG, superior temporal gyrus.

MTG ITG

Orb

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5  Coronal Sections This is the first of three chapters showing sections of entire human brains, in this case illustrating approximately coronal planes. Forebrain structures are emphasized, but parts of the brainstem and cerebellum are indicated as well. The organization of various functional systems in the forebrain (e.g., thalamus, hippocampus) and other parts of the central nervous system is presented in Chapter 8. Drawings showing typical areas of arterial supply in each section are also provided in this and the next two chapters. We simplified these in two major ways. First, arterial territories are shown as sharply demarcated from each other, when in reality there is significant interdigitation and overlap. Second, perforating arteries arise from all the vessels of the circle of Willis, but we lumped together those from the posterior communicating and posterior cerebral arteries, and those from the anterior communicating and anterior cerebral arteries.

Cingulate gyrus

Septum pellucidum

Fornix Thalamus

Corpus callosum Anterior commissure Optic chiasm Hypothalamus (tuberal part)

Hypothalamus (mammillary body)

Figure 5.1  The hemisected brain from Fig. 1.7, used in much of this chapter to indicate planes of section.

Lateral ventricle

Third ventricle

5-6 5-7 5-8 5 5-1-9 5-101 5-12

5-4 5-5

Amygdala

Lateral ventricle Thalamus

Putamen Third ventricle

Caudate nucleus Amygdala

5-8 5-9 5-10 5-11 5-12

5-7

5-6

5-4

Hypothalamus

5-5

Hippocampus Fourth ventricle Caudate nucleus

Figure 5.2  The planes of section shown in this chapter, indicated on three-dimensional reconstructions. (Courtesy Dr. John W. Sundsten, Department of Biological Structure, University of Washington School of Medicine.)

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Figure 5.3  (A–X) Twenty-four coronal sections of a brain, arranged in an anterior-to-posterior sequence from the anterior edge of the corpus callosum to the beginning of the occipital lobe.

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2

1

4 (A) Anterior end of the genu of the corpus callosum (1). Convolutions that compose most of the frontal lobe are the superior (3), middle (4), and inferior (5) frontal gyri, orbital gyri (6), and gyrus rectus (8). The cingulate gyrus (2) is cut twice, once above and once below the genu of the corpus callosum. The olfactory sulcus (7), which will be occupied by the olfactory tract at a slightly more posterior level, lies just lateral to gyrus rectus.

5

8

(B) The anterior horn of the lateral ventricle (3) appears. A septum pellucidum (2) forms the medial wall of each lateral ventricle. The corpus callosum is now cut in two places, once through its body (1) above the septum pellucidum and once (4) as the genu begins to taper into the rostrum below the septum pellucidum.

6

7

1 2

3

4

A

D

1

2 (C) The head of the caudate nucleus (1) appears in the lateral wall of the lateral ventricle. The anterior region of the insula (2) is also visible at this level, overlying the caudate nucleus.

1

2

3 4 5 (D) The rostral end of the putamen (3) is separated from the head of the caudate nucleus (1) by the anterior limb of the internal capsule (2). The putamen, the larger of the two parts of the lenticular nucleus, is overlain for its entire extent by the insula (4). The olfactory tract (7) lies in the olfactory sulcus, just lateral to gyrus rectus (8). The section passes through the tip of the temporal lobe (6), separated from the frontal lobe by the lateral sulcus (5).

6 8

7

CHAPTER 5  Coronal Sections

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Figure 5.3 (Continued) Coronal sections. (E) The globus pallidus (5) makes its appearance medial to the putamen (4); the two together compose the lenticular nucleus. Nucleus accumbens (6), the region of continuity between the putamen and the head of the caudate nucleus (2), is also apparent. The septum pellucidum (1) is continuous with the septal nuclei (7). (The proximity of nucleus accumbens to the septal nuclei was reflected in its earlier but now outmoded name, nucleus accumbens septi—“the nucleus leaning against the septum.”) The anterior limb of the internal capsule (3) still occupies the cleft between the lenticular nucleus and the head of the caudate nucleus. Shown enlarged in Fig. 5.4.

1 2 3 4 5 7

6 1

9

2

(F) The level of the interventricular foramen (1) and anterior commissure (5) is a transition point for many structures—for example, from the head to the body of the caudate nucleus (2) and from the anterior horn to the body of the lateral ventricle (9). This section shaves off the anterior end of the thalamus (3), passes through the genu of the internal capsule (4), and cuts the fornix twice (8) as it curves ventrally toward the hypothalamus. The olfactory tract (6) joins the base of the forebrain, and the optic chiasm (7) appears. Shown enlarged in Fig. 5.5.

8

3

4

5

7

6 1

13

2 12 E H

3

11

4

10

5 6

7

8

9

(G) Anterior diencephalon. Characteristic diencephalic features include the third ventricle (12), hypothalamus (8) with its attached infundibulum (7), and thalamic nuclei—anterior (1) and ventral anterior (2). The external (3) and internal (4) segments of the globus pallidus are now apparent, as is the anterior end of the amygdala (9). Fibers that will cross in the anterior commissure (5) accumulate beneath the lenticular nucleus. The fornix is cut twice, through the body (13) and column (10). The optic tract (6) and posterior limb of the internal capsule (11) are also present.

1

8

2

7 3

4

5 6

(H) The mammillothalamic tract (7) enters the anterior nucleus (8) of the thalamus. The two thalami fuse in the interthalamic adhesion (1) or massa intermedia, which bridges the third ventricle (6). The ansa lenticularis (3, literally “the handle of the lenticular nucleus”) emerges from the inferior surface of the globus pallidus and hooks around the posterior limb of the internal capsule (2). The amygdala (4) is larger, and the middle of the three zones of the hypothalamus (the tuberal zone, 5) is present. Shown enlarged in Fig. 5.6. Illustration continued on following page

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Figure 5.3 (Continued) Coronal sections. (I) Additional efferents from the globus pallidus penetrate the posterior limb of the internal capsule (2) as the lenticular fasciculus and collect on the other side (1) before entering the thalamus. The column of the fornix (4) continues through the hypothalamus, where it will soon end in the mammillary body. The surface of the temporal lobe includes the superior (3), middle (5), and inferior (6) temporal gyri and the occipitotemporal gyrus (7), adjacent to the parahippocampal (8) gyrus. The amygdala (9) has reached nearly maximal size.

1 2

3 4 9 8

5 7

6

(J) Midthalamus. The dorsomedial (2) and ventrolateral (3) nuclei are prominent at this level. The optic tract (6) proceeds posteriorly toward its thalamic termination in the lateral geniculate nucleus. The column of the fornix is ending in the mammillary body (10), which in turn gives rise to the mammillothalamic tract (9). The lateral ventricle is another in a series of forebrain structures to be cut twice, here through the body (1) and through the inferior horn (8), which has appeared adjacent to the amygdala (7). Both the putamen (4) and the globus pallidus (5) begin to get smaller.

1

2 3 4 5 6 7

10

9

8

1

2 IL 3 4 (K) Level of the mammillary bodies (7) of the hypothalamus. Efferents from the globus pallidus and cerebellum collect beneath the thalamus in the thalamic fasciculus (2) before moving dorsally into the ventral lateral (1) and ventral anterior (see Fig. 5.3G) nuclei. The appropriately named subthalamic nucleus (3) appears beneath the thalamus. The amygdala (4) begins to get smaller, and the hippocampus (6) assumes a position adjacent to the inferior horn of the lateral ventricle (5). Shown enlarged in Fig. 5.7.

7

5 6 1

10

2

3 9 4 (L) Brainstem structures begin to appear. The rostral end of the substantia nigra (8) is adjacent to the subthalamic nucleus (9). Many fibers in the posterior limb of the internal capsule (3) continue into the cerebral peduncle (7). Several structures are now cut twice, such as the body (1) and inferior horn (6) of the lateral ventricle and the body (2) and tail (4) of the caudate nucleus. The hippocampus (5) has almost completely replaced the amygdala on the right side of the section; the fornix (10), the most prominent output bundle of the hippocampus, proceeds anteriorly in its characteristic trajectory medial to the lateral ventricle.

8

7 6

5

CHAPTER 5  Coronal Sections

57

Figure 5.3 (Continued) Coronal sections. (M) The dorsomedial (1), ventral posteromedial (2), and ventral posterolateral (3) nuclei now account for most of the thalamus. The putamen (5) and globus pallidus (6) continue to get smaller, as does the overlying insula (4). Cerebellar efferents (8) proceed rostrally toward the ventral lateral nucleus of the thalamus (see Fig. 5.3K), and the optic tract (7) continues posteriorly toward the lateral geniculate nucleus. The posterior limb (10) and sublenticular part (9) of the internal capsule partially surround the lenticular nucleus. Shown enlarged in Fig. 5.8.

1 2

3 10 4 5 9 6 8

7

(N) Posterior to the lenticular nucleus, the third ventricle (1) is smaller as the plane of section gets closer to the cerebral aqueduct. Cerebellar efferents (2) that have passed through or around the red nucleus (4) collect beneath the thalamus. The optic tract (3) begins to terminate in the lateral geniculate nucleus (5) on the right side of the section.

1

2 5 3

4 1 2 M P 7 3

5

4

(O) Near the diencephalon-midbrain junction, the lateral geniculate nucleus (4) is present on both sides, and the largest of the thalamic intralaminar nuclei, the centromedian nucleus (3), is apparent. The habenula (2) gives rise to the habenulointerpeduncular tract (7). Fornix fibers are cut twice, this time where they are suspended from the corpus callosum as the posterior part of the body (1) and where they are still attached to the hippocampus (6) as the fimbria (5). Shown enlarged in Fig. 5.9.

6

8

1 2

3 7 4

5

6

(P) Posterior commissure (1), at the diencephalon-midbrain junction. The third ventricle has been replaced by the cerebral aqueduct (7), and a bit of the basal pons (6) appears, accompanied by the basilar artery (5). The only parts of the thalamus left are the pulvinar (2) and the medial (3) and lateral (4) geniculate nuclei. The pineal gland (8) is in the midline just above the posterior commissure. Shown enlarged in Fig. 5.10. Illustration continued on following page

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Figure 5.3 (Continued) Coronal sections. (Q) Posterior thalamus. Only the pulvinar (6) and the medial geniculate nucleus (9) remain. The plane of section approaches the posterior edge of C-shaped telencephalic structures, so the two parts of twice-cut structures draw closer together—the crus of the fornix (13) and fimbria of the hippocampus (12), the body (5) and tail (7) of the caudate nucleus, and the body (4) and inferior horn (8) of the lateral ventricle. Several brainstem structures are apparent, including the aqueduct (2) surrounded by periaqueductal gray (3), the medial lemniscus (10), and the now-crossed superior cerebellar peduncle (11). The pineal gland (1) is still present above the most rostral part of the midbrain (the pretectal area). Shown enlarged in Fig. 5.11.

2

1

3 4

13 5 6 7 8 12 11

(R) Splenium of the corpus callosum (1). The section passes tangentially through the posterior edge of the caudate nucleus (8), through fibers of the fornix as they pass from the fimbria (5) into the crus (3), and through the lateral ventricle as the body (4) joins the inferior horn (6). The superior colliculus (9) and the decussation of the superior cerebellar peduncles (7) can be seen in the brainstem. A little piece of the pulvinar (2) is all that remains of the thalamus. Shown enlarged in Fig. 5.12.

9

1

2

9

10

3 4

8 5

6 7 1 2

Q T

5 3

(S) Now the section passes tangentially through the posterior end of the hippocampus (3) as it curves up underneath the splenium of the corpus callosum (1) and through the crus (2) of the fornix, the atrium (5) of the lateral ventricle, and the decussation of the superior cerebellar peduncles (4).

4 1 2

7

3 (T) Posterior edge of the splenium of the corpus callosum (1). The section passes through an enlarged mass of choroid plexus (the glomus, 7) that projects back into the posterior horn of the lateral ventricle, and through remnants of the hippocampus (2). The cerebellar hemispheres (4) begin to appear, the lateral lemniscus (3) ends in the inferior colliculus (6), and the trigeminal nerve (5) is attached to the pons.

6 5

4

CHAPTER 5  Coronal Sections

59

Figure 5.3 (Continued) Coronal sections.

1

2

(U) Choroid plexus (3) still protrudes into the posterior horn of the lateral ventricle. The aqueduct (1) begins to enlarge into the rostral part of the fourth ventricle. The lateral (2) and medial (4) lemnisci and the superior cerebellar peduncle (5) are apparent in the pons.

3

4

5 (V) Last bit of the posterior horn of the lateral ventricle (3). The cerebellar vermis (1), hemispheres (5), and flocculus (8, actually part of each hemisphere) can now be distinguished. The aqueduct has opened into the fourth ventricle (2), and the superior (4) and middle (6) cerebellar peduncles and the pyramid (7) are present.

1

2

3

4

5 6

8

7

1

2

U

3 4 3

5 2

X

(W) Pons and medulla. The fourth ventricle (1) and pyramid (5) are large, and the inferior olivary nucleus (4) is now present. The superior cerebellar peduncle (2) leaves the cerebellum, and the inferior cerebellar peduncle (6) enters. The cerebellar flocculus (3) is still located adjacent to the pontomedullary junction.

6

1

4

(X) Deep cerebellar nuclei (1) (termed dentate, interposed, and fastigial nuclei—laterally to medially) and nodulus (2). The calcarine sulcus (3), with visual cortex in its upper and lower banks (4), deeply indents the medial surface of the occipital lobe.

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Nolte’s The Human Brain in Photographs and Diagrams

A

Anterior cerebral artery Anterior cerebral artery (perforating branches) Middle cerebral artery Middle cerebral artery (perforating branches)

Corpus callosum (body)

Superior frontal gyrus

Longitudinal fissure

Lateral ventricle (anterior horn)

Caudate nucleus

Middle frontal gyrus

(head)

Cingulate gyrus Internal capsule

Inferior frontal gyrus

(anterior limb)

Putamen

Lateral sulcus

Insula

Superior temporal gyrus

Globus pallidus Middle temporal gyrus Gyrus rectus

Middle cerebral artery Olfactory tract

Anterior cerebral artery

Inferior temporal gyrus

Figure 5.4  (A) A coronal section at the level of the anterior limb of the internal capsule.

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CHAPTER 5  Coronal Sections

B

Septal nuclei

Septum pellucidum

Caudate nucleus (head)

Septal vein

Putamen Internal capsule (anterior limb)

Globus pallidus (external segment)

Claustrum

Lenticulostriate arteries

Anterior commissure

Nucleus accumbens

(olfactory component)

Figure 5.4 (Continued) (B) The central region of Fig. 5.4A, enlarged.

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A

Anterior cerebral artery Anterior cerebral artery (perforating branches) Middle cerebral artery Middle cerebral artery (perforating branches)

Superior frontal gyrus

Longitudinal fissure Corpus callosum (body)

Middle frontal gyrus Caudate nucleus (junction between head & body)

Cingulate gyrus Lateral ventricle

Internal capsule

(junction between anterior horn & body)

(genu)

Choroid plexus

Inferior frontal gyrus

Thalamus Insula

Lateral sulcus

Superior temporal gyrus Putamen

Globus pallidus

Middle temporal gyrus Parahippocampal gyrus

Middle cerebral branches

Anterior commissure

Figure 5.5  (A) A coronal section at the level of the anterior commissure.

Inferior temporal gyrus

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CHAPTER 5  Coronal Sections

B

Anterior nucleus

Interventricular foramen (of Monro)

Fornix (body)

Septum pellucidum

Septal nuclei

Caudate nucleus (head/body)

Terminal (thalamostriate) vein

Stria terminalis

Thalamic reticular nucleus

Internal capsule (genu)

External capsule Globus pallidus: external segment internal segment

Extreme capsule Fornix (column)

Putamen

Ventral pallidum

Claustrum

Basal nucleus (of Meynert)

Olfactory tract

Optic nerve (CN II)

Optic chiasm

Basal forebrain

Figure 5.5 (Continued) (B) The central region of Fig. 5.5A, enlarged.

Lenticulostriate arteries

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Nolte’s The Human Brain in Photographs and Diagrams

A

Anterior cerebral artery Anterior choroidal artery Middle cerebral artery Middle cerebral artery (perforating branches) Posterior cerebral artery Posterior cerebral artery (perforating branches) Corpus callosum Transverse fissure

(body)

Choroid plexus Caudate nucleus

Cingulate gyrus

(body)

Lateral ventricle

Internal capsule

(body)

(posterior limb)

Thalamus Lateral sulcus Superior temporal gyrus

Putamen

Insula Middle temporal gyrus Globus pallidus Third ventricle

Parahippocampal gyrus

Inferior temporal gyrus

Occipitotemporal (fusiform) gyrus

Figure 5.6  (A) A coronal section at the level of the ansa lenticularis and the anterior thalamus.

Amygdala

65

CHAPTER 5  Coronal Sections

B

Interthalamic adhesion Dorsomedial nucleus

Septum pellucidum Fornix (body)

Internal cerebral vein

Anterior nucleus Stria terminalis

Terminal (thalamostriate) vein Mammillothalamic tract

Caudate nucleus (body)

Internal capsule

Reticular nucleus + external medullary lamina

(posterior limb)

Putamen

Ventral lateral nucleus (VL)

Globus pallidus:

Lenticular fasciculus

external segment internal segment

Lenticulostriate arteries

Claustrum Ventral amygdalofugal pathway

Anterior commissure Basal nucleus (of Meynert)

Basal forebrain

Ansa lenticularis

Hypothalamus (tuberal region)

Fornix (column)

Optic tract

Figure 5.6 (Continued) (B) The central region of Fig. 5.6A, enlarged.

Amygdala

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A

Anterior cerebral artery Anterior choroidal artery Middle cerebral artery Middle cerebral artery (perforating branches) Posterior cerebral artery Posterior cerebral artery (perforating branches) Corpus callosum (body)

Longitudinal fissure

Lateral ventricle (body)

Cingulate gyrus Transverse fissure Choroid plexus

Caudate nucleus Internal capsule (posterior limb)

Thalamus

Insula

Lateral sulcus Putamen

Superior temporal gyrus

Globus pallidus Middle temporal gyrus

Amygdala

Caudate nucleus

Hippocampus Third ventricle

Inferior temporal gyrus

Parahippocampal gyrus Occipitotemporal (fusiform) gyrus Figure 5.7  (A) A coronal section at the level of the mammillary bodies.

Lateral ventricle (inferior horn)

Collateral sulcus

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CHAPTER 5  Coronal Sections

B

Ventral lateral nucleus (VL)

Dorsomedial nucleus

Stria medullaris

Fornix

Internal cerebral (of the thalamus) vein

(body)

Lateral dorsal nucleus

Stria terminalis

Terminal (thalamostriate) vein Caudate nucleus

Reticular nucleus + external medullary lamina

(body)

Internal medullary lamina

Ventral posterolateral nucleus (VPL)

Internal capsule (posterior limb)

Thalamic fasciculus

Putamen

Zona incerta

Claustrum Lenticular fasciculus Globus pallidus: external segment internal segment

Optic tract

Caudate nucleus

Stria terminalis Subthalamic nucleus

(tail)

Hypothalamus (posterior region)

Mammillary body

Fornix (column)

Mammillothalamic tract

Figure 5.7 (Continued) (B) The central region of Fig. 5.7A, enlarged.

Amygdala

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A

Anterior cerebral artery Anterior choroidal artery Middle cerebral artery Middle cerebral artery (perforating branches) Posterior cerebral artery Posterior cerebral artery (perforating branches)

Cingulate gyrus

Longitudinal fissure

Corpus callosum (body)

Transverse fissure Choroid plexus Lateral ventricle (body)

Caudate nucleus

Thalamus

Insula

Lateral sulcus Internal capsule (posterior limb)

Superior temporal gyrus Internal capsule (sublenticular part)

Putamen Globus pallidus

Middle temporal gyrus

Hippocampus

Lateral ventricle (inferior horn)

Caudate nucleus Third ventricle Cerebral peduncle

Parahippocampal gyrus

Occipitotemporal (fusiform) gyrus

Collateral sulcus

Inferior temporal gyrus Figure 5.8  (A) A coronal section at the level of the anterior end of the hippocampus.

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CHAPTER 5  Coronal Sections

B

Stria terminalis

Lateral dorsal nucleus

Dorsomedial nucleus

Stria medullaris (of the thalamus)

Internal cerebral vein

Fornix (body)

Ventral lateral nucleus (VL)

Terminal (thalamostriate) vein Caudate nucleus (body)

Reticular nucleus + external medullary lamina

Red nucleus (rostral end)

Ventral posterolateral nucleus (VPL)

Internal capsule (posterior limb)

Centromedian nucleus

Putamen

Ventral posteromedial nucleus (VPM)

Claustrum Globus pallidus

Parafascicular nucleus

Internal capsule

Stria terminalis

(sublenticular part)

Choroid plexus

Caudate nucleus (tail)

Subthalamic nucleus Substantia nigra

Cerebellothalamic fibers

Cerebral peduncle

Hippocampus

Figure 5.8 (Continued) (B) The central region of Fig. 5.8A, enlarged.

Optic tract

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A

Anterior cerebral artery Anterior choroidal artery Basilar artery Middle cerebral artery Middle cerebral artery (perforating branches) Posterior cerebral artery Posterior cerebral artery (perforating branches) Corpus callosum (body)

Longitudinal fissure

Transverse fissure Cingulate gyrus Lateral ventricle (body)

Choroidal vein

Caudate nucleus

Choroid plexus

Lateral sulcus Thalamus Superior temporal gyrus

Third ventricle Middle temporal gyrus Lateral ventricle

Hippocampus

(inferior horn)

Parahippocampal gyrus Cerebral peduncle

Occipitotemporal (fusiform) gyrus Figure 5.9  (A) A coronal section through the posterior third of the thalamus.

Caudate nucleus Inferior temporal gyrus Collateral sulcus

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CHAPTER 5  Coronal Sections

B

Ventral lateral nucleus (VL)

Lateral posterior nucleus

Dorsomedial nucleus

Internal cerebral vein

Fornix (body)

Habenula

Terminal (thalamostriate) vein Caudate nucleus

Reticular nucleus + external medullary lamina

(body)

Stria terminalis Habenulointerpeduncular tract

Centromedian nucleus

Red nucleus Ventral posterolateral nucleus (VPL)

Stria terminalis Caudate nucleus (tail)

Ventral posteromedial nucleus (VPM)

Fimbria (fornix fibers)

Lateral geniculate nucleus

Hippocampus: hippocampus proper dentate gyrus subiculum

Choroid plexus Optic tract

Parafascicular nucleus

Oculomotor nerve (CN III)

Cerebral peduncle

Figure 5.9 (Continued) (B) The central region of Fig. 5.9A, enlarged.

Substantia nigra: compact part reticular part

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A

Anterior cerebral artery Anterior choroidal artery Basilar artery Middle cerebral artery Middle cerebral artery (perforating branches) Posterior cerebral artery Posterior cerebral artery (perforating branches) Corpus callosum

Longitudinal fissure

(body)

Cingulate gyrus Transverse fissure

Lateral ventricle (body)

Choroid plexus Caudate nucleus Insula Thalamus Lateral sulcus Superior temporal gyrus Caudate nucleus Middle temporal gyrus Lateral ventricle (inferior horn)

Inferior temporal gyrus Hippocampus

Cerebral peduncle

Parahippocampal gyrus

Basilar artery

Basal pons Collateral sulcus

Figure 5.10  (A) A coronal section at the level of the posterior commissure.

Occipitotemporal (fusiform) gyrus

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CHAPTER 5  Coronal Sections

B

Caudate nucleus

Pulvinar

Pineal gland

Internal cerebral vein

Fornix (crus/body)

Posterior commissure

Terminal (thalamostriate) vein

(body)

External medullary lamina

Stria terminalis

Reticular nucleus Pretectal area

Medial geniculate nucleus

Periaqueductal gray

Lateral geniculate nucleus

Stria terminalis Choroid plexus

Caudate nucleus

Fimbria

(tail)

(fornix fibers)

Hippocampus:

Cerebral aqueduct

hippocampus proper dentate gyrus subiculum

Cerebral peduncle

Oculomotor nucleus

Ventral tegmental area

Substantia nigra: compact part reticular part

Figure 5.10 (Continued) (B) The central region of Fig. 5.10A, enlarged.

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A

Anterior cerebral artery Anterior choroidal artery Basilar artery Middle cerebral artery Middle cerebral artery (perforating branches) Posterior cerebral artery Posterior cerebral artery (perforating branches) Superior cerebellar artery Corpus Longitudinal callosum Cingulate fissure (splenium) gyrus Superior cistern (continuous with transverse fissure)

Lateral ventricle

Caudate nucleus

(body)

Thalamus Choroid plexus Lateral sulcus Stria terminalis

Superior temporal gyrus Middle temporal gyrus

Lateral ventricle (inferior horn)

Caudate nucleus

Hippocampus

Inferior temporal gyrus

Cerebral peduncle

Occipitotemporal (fusiform) gyrus Collateral sulcus

Parahippocampal gyrus

Basilar artery

Basal pons

Figure 5.11  (A) A coronal section that passes tangentially through the stria terminalis.

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CHAPTER 5  Coronal Sections

B

Terminal (thalamostriate) vein

Pulvinar

Pineal gland

Internal cerebral vein

Fornix (crus)

Cerebral aqueduct

Periaqueductal gray

Caudate nucleus (body)

Pretectal area

Stria terminalis Stria terminalis

Reticular nucleus + external medullary lamina

Fimbria (fornix fibers)

Stria terminalis Caudate nucleus

Choroid plexus

(tail)

Lateral geniculate nucleus

Hippocampus: hippocampus proper dentate gyrus subiculum

Brachium of the superior colliculus

Medial geniculate nucleus

Spinothalamic tract Medial lemniscus Cerebral peduncle

Oculomotor nucleus

Ventral tegmental area

Superior cerebellar peduncle

Substantia nigra: compact part reticular part

Figure 5.11 (Continued) (B) The central region of Fig. 5.11A, enlarged.

Posterior cerebral branch

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A

Anterior cerebral artery Anterior choroidal artery Basilar artery Middle cerebral artery Middle cerebral artery (perforating branches) Posterior cerebral artery Posterior cerebral artery (perforating branches) Superior cerebellar artery

Cingulate gyrus

Corpus callosum

Longitudinal fissure

(splenium)

Superior cistern (continuous with transverse fissure)

Lateral ventricle (body)

Fornix (crus)

Choroid plexus Caudate nucleus (body/tail)

Fimbria (fornix fibers)

Lateral ventricle (inferior horn)

Hippocampus Parahippocampal gyrus

Basilar artery

Basal pons

Thalamus

Figure 5.12  (A) A coronal section that passes tangentially through the fornix and caudate nucleus.

CHAPTER 5  Coronal Sections

B

Caudate nucleus

Pulvinar

Superior colliculus

Cerebral aqueduct

Periaqueductal gray

(body/tail)

Hippocampus:

Fimbria

hippocampus proper dentate gyrus subiculum

(fornix fibers)

Brachium of the inferior colliculus Spinothalamic tract

Oculomotor nucleus (caudal end)

Medial lemniscus Medial longitudinal fasciculus (MLF) Decussation of the superior cerebellar peduncles Figure 5.12 (Continued) (B) The central region of Fig. 5.12A, enlarged.

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6  Axial Sections This chapter, the second of three showing sections of entire human brains, illustrates axial planes approximating those used in computed tomography scans (see Chapter 9). Forebrain structures continue to be emphasized, but parts of the brainstem and cerebellum are indicated as well. The organization of various functional systems in the forebrain (e.g., thalamus, hippocampus) is presented in Chapter 8. Colored diagrams showing typical areas of arterial supply in each section are provided in this and the preceding and following chapter. We simplified these in two major ways. First, arterial territories are shown as sharply demarcated from each other, when in reality there is significant interdigitation and overlap. Second, perforating arteries arise from all the vessels of the circle of Willis, but we lumped together those from the posterior communicating and posterior cerebral arteries, and those from the anterior communicating and anterior cerebral arteries.

Cingulate gyrus

Septum pellucidum

Fornix Thalamus

Corpus callosum Anterior commissure Optic chiasm Hypothalamus (tuberal part)

Hypothalamus (mammillary body)

Figure 6.1  The hemisected brain from Fig. 1.7, used in much of this chapter to indicate planes of section.

Lateral ventricle

Third ventricle 6-11 6-10 6-9 6-8 6-7 6-6 6-5

Amygdala

6-4

Hippocampus Fourth ventricle Hypothalamus Thalamus

Third ventricle

Lateral ventricle Caudate nucleus Putamen

6-11 6-10

6-9

Caudate nucleus Amygdala

6-8 6-7 6-6 6-5 6-4

Figure 6.2  The planes of section shown in this chapter, indicated on three-dimensional reconstructions. (Courtesy Dr. John W. Sundsten, Department of Biological Structure, University of Washington School of Medicine.)

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Figure 6.3  (A–X) Twenty-four axial sections of a brain, arranged in an inferior-to-superior sequence extending from the orbital surface of the frontal lobe to just above the corpus callosum. Anterior is toward the top, as in the conventional orientation of computed tomography (CT) and magnetic resonance (MR) images (Chapter 9); as a result the brainstem, when present, is inverted relative to its orientation in Chapter 3.

1 8

2 3 4

(A) The first section just reaches the orbital surface of the frontal lobe, including gyrus rectus (2) and the beginning of other parts of the orbital frontal cortex (1), and passes through the olfactory sulcus (8) and olfactory tract (3). The temporal pole (4) can also be seen. The brainstem is cut at an odd angle in these sections, with more rostral parts toward the top. This section passes through the basal pons (5) and the inferior olivary nucleus (7) of the medulla. The corticospinal tract (6) can be seen passing from the basal pons into the medullary pyramid.

5 6 7

(B) Gyrus rectus (2) is still present, joined by a little more of the orbital frontal cortex (1). The section again passes through the basal pons (4) and the basilar artery (3) anterior to it, as well as parts of the rostral medulla. It includes the cerebellar flocculus (5), the inferior cerebellar peduncle (6), the vestibulocochlear (8) nerve, and choroid plexus (7) in the lateral aperture of the fourth ventricle.

1 2

3 8

4 5

7

6

1

D A

2 3 4 5

(C) The olfactory tract (1) has now reached the posterior end of the olfactory sulcus, near where it attaches to the base of the forebrain. The optic nerve (2) moves posteriorly toward the optic chiasm; the internal carotid artery (3) is just lateral to where the optic chiasm will soon be located. The inferior horn of the lateral ventricle (5) and adjacent amygdala (4) begin to appear in the temporal lobe. The inferior cerebellar peduncle (6) turns posteriorly toward the cerebellum.

6

1

9

2 3 4

(D) The middle cerebral artery (1) moves laterally into the lateral sulcus. The amygdala (3) is larger, and the hippocampus (4) appears just posterior to it; both structures underlie the uncus (2). The plane of section moves closer to the hypothalamus and passes through the infundibulum (9). The middle cerebellar peduncle (6) connects the basal pons (5) to the cerebellum. The inferior cerebellar peduncle (7) has completed its posterior turn and is now cut in cross section as it moves into the cerebellum. The oculomotor nerve (8) moves anteriorly from its point of emergence from the brainstem.

8

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CHAPTER 6  Axial Sections

81

Figure 6.3 (Continued) Axial sections. (E) The anterior cerebral artery (2) moves into the longitudinal fissure (1), and the middle cerebral artery (4) continues on its course toward the insula. The optic nerves partially decussate in the optic chiasm (3). The amygdala (5) and hippocampus (6) continue to increase in size. The cerebellar vermis (8) and hemispheres (9) can be distinguished, and the middle cerebellar peduncle (7) still connects the basal pons to the cerebellum. Shown enlarged in Fig. 6.4.

1 2 3 4 5 6 7 8 9

(F) The optic tract (1) begins to move posteriorly from the optic chiasm, and the plane of section reaches the tuberal zone of the hypothalamus (2). The superior cerebellar peduncle (5) leaves the deep cerebellar nuclei (represented here by the dentate nucleus [6]), forms part of the wall of the fourth ventricle (4), and enters the pons. The first part of the midbrain to appear in this plane of section is the cerebral peduncle (3).

1

2 3 4 5 6

H

E

1 2 3 4

5 6 7 8 9

(G) The base of the forebrain, beginning to pass through the head of the caudate nucleus (1), the putamen (5), the nucleus accumbens (6), and the anterior limb of the internal capsule (2). The insula (3), buried in the lateral sulcus (4), overlies the putamen. The mammillary bodies (8) and other parts of the hypothalamus border the third ventricle (7). The cerebral peduncle (9) and substantia nigra (10) are apparent in the midbrain. The superior cerebellar peduncle (12) leaves the dentate nucleus (13), enters the brainstem, and decussates (11). Shown enlarged in Fig. 6.5.

10 11 12 2

1

18

3 4 5 6 7

17 16 15 14

8

13

9

12

10 11

(H) The lateral ventricle is now cut twice, through the anterior (2) and inferior (7) horns, and the corpus callosum (1) makes its first appearance. The limbic lobe is also cut twice, through the cingulate (18) and parahippocampal (13) gyri. The head of the caudate nucleus (3), the putamen (5), the nucleus accumbens (17) and the anterior limb of the internal capsule (4) all increase in size. Fibers that will cross in the anterior commissure (6) begin to move toward the midline, and the optic tract (15) continues to move posteriorly. The column of the fornix (16) and the mammillothalamic tract (14) are transected just above each mammillary body. All of the deep cerebellar nuclei (12) are now apparent. The vast majority of efferents from these nuclei travel through the superior cerebellar peduncle (11) and decussate (10), and then most of them (9) pass through or around the red nucleus (8). Shown enlarged in Fig. 6.6. Illustration continued on following page

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Figure 6.3 (Continued) Axial sections.

13

1

12 (I) The subcallosal gyrus (1), the last bit of limbic cortex adjacent to the corpus callosum, borders the longitudinal fissure (13). The head of the caudate nucleus (2) continues; both parts of the lenticular nucleus—the putamen (3) and the globus pallidus (4)—are now apparent, and the subthalamic nucleus (6) can be seen just across the internal capsule/cerebral peduncle (5) from the globus pallidus. Fornix fibers are cut twice, once through the fimbria (9) as it leaves the hippocampus (8) and again through the column of the fornix (11) as it approaches the mammillary body. The mammillothalamic tract (10) continues on its course toward the anterior nucleus of the thalamus. Fibers of the anterior commissure (12) cross the midline. The dentate nucleus (7) is the only deep cerebellar nucleus remaining.

2

11

3

10

4

9

5

8

6

7

(J) The section passes tangentially through the corpus callosum as the genu (1) tapers into the rostrum (2). The anterior commissure (3), column of the fornix (4), and subthalamic nucleus (5) are still visible, and the inferior colliculus (6) appears. Shown enlarged in Fig. 6.7.

1 2 3 4 5

6

L I

1 2 3

4 (K) The septum pellucidum (1), merging with the septal nuclei (2), succeeds the rostrum of the corpus callosum. The lateral (3) and medial (4) geniculate nuclei (the most inferior parts of the thalamus) can now be seen, and the continuity of the third ventricle (6) and the cerebral aqueduct (5) is apparent.

6

5

10

1 2

3 4 5

9 (L) Choroid plexus (1) passes through each interventricular foramen adjacent to the column of the fornix (10). Four of the five parts of the internal capsule—the anterior limb (2), genu (3), posterior limb (4), and retrolenticular part (5) —are now present, as is much more of the thalamus (6). The mammillothalamic tract (9) continues on its path toward the anterior nucleus of the thalamus. The posterior commissure (7) crosses the midline near the periaqueductal gray (8). Shown enlarged in Fig. 6.8.

6 8

7

CHAPTER 6  Axial Sections

83

Figure 6.3 (Continued) Axial sections. (M) The septum pellucidum (1) still separates the anterior horns of the two lateral ventricles from each other. The globus pallidus (2) gets smaller as the plane of section moves superiorly through the lenticular nucleus. Lateral (3) and medial (4) divisions of the thalamus can be distinguished because of differences in the numbers of myelinated fibers entering and leaving them. The superior colliculus (5) appears in the midbrain.

1 2 3 4 5

(N) Now more parts of the thalamus can be seen: the lateral (2) and medial (3) divisions, the anterior (1) and centromedian (4) nuclei, and the pulvinar (5). (The mammillothalamic tract has terminated in the anterior nucleus and is no longer visible.) The pineal gland (6) protrudes posteriorly between the superior colliculi (7). Shown enlarged in Fig. 6.9.

1 2 3 4 5 6

7

P M

1 2 3

4

(O) The plane of section is above the globus pallidus, and now the putamen (1) begins to get smaller. The stria medullaris of the thalamus terminates in the habenula (2). The hippocampus (3) and pineal gland (4) are still apparent.

1 2 3 4 5 (P) In the thalamus, lateral (3) and medial (2) divisions, the anterior nucleus (1), and the pulvinar (5) can still be distinguished. Fibers travel posteriorly in the stria medullaris (4) of the thalamus toward the habenula. Shown enlarged in Fig. 6.10. Illustration continued on following page

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Figure 6.3 (Continued) Axial sections.

1 2 (Q) The putamen (3) continues to get smaller, as does the overlying insula (4). As the plane of section moves upward through the cerebral hemisphere, the profiles of twice-cut structures, such as the lateral ventricle (1, 6) and fornix fibers (2, 5), will draw progressively closer to each other until these C-shaped structures are finally cut tangentially (e.g., T, V).

3 4 5 6

(R) Near the top of the putamen (3) and internal capsule (2). The fornix (1) is now cut obliquely as it begins to curve downward toward the interventricular foramen. Although the thalamus begins to get smaller, medial (6) and lateral (5) divisions, the anterior nucleus (4), and the pulvinar (7) can still be distinguished.

1 2 3 4 5 6 7

T Q 1

2 3

4 (S) Just below the splenium of the corpus callosum and completely above the putamen. The head of the caudate nucleus (1) begins to taper into the body of the caudate nucleus, and the posterior part of the hippocampus (5) has a distinctive pattern of folding (compare with R). The plane of section still passes through the inferior horn (4) but will soon enter the atrium and posterior horn of the lateral ventricle. The fornix (2) is cut obliquely once again. The internal cerebral vein (3) of each hemisphere travels posteriorly toward the great cerebral vein. Shown enlarged in Fig. 6.11.

5

9 1 2 3 8

4 5

(T) The corpus callosum is now cut twice, through the body (9) and the splenium (4). The thalamus (3) continues to dwindle, the distinctive appearance of the hippocampus (7) continues, and the two profiles of the lateral ventricle (1, 6) draw closer together. On the right side of the section, fornix fibers are still cut twice (2, 5), but on the left side the section cuts tangentially through these fibers (8), showing their entire course as they pass from the fimbria to the fornix.

7

6

CHAPTER 6  Axial Sections

85

Figure 6.3 (Continued) Axial sections. (U) The plane of section has nearly reached the top of several C-shaped forebrain structures. It passes tangentially through the fornix (3), but still cuts the corpus callosum (1, 6), caudate nucleus (2, 4), and lateral ventricle (7, 8) twice. The last bit of the hippocampus (5) can be seen adjacent to the splenium of the corpus callosum (6).

1

2

8

3 4 5

7 6 (V) A tangential section through the body of the caudate nucleus (2), the lateral ventricle (3), and the body of the corpus callosum (4). The limbic lobe is still cut twice, once (nearly tangentially) through the cingulate gyrus (1) and again through the narrow isthmus (5) joining the cingulate and parahippocampal gyri.

1 2

3 4 5

X U

1

2

3

(W) A tangential cut through the corpus callosum (2), lateral ventricle (3), and a larger expanse of the cingulate gyrus (1).

1

2

(X) Finally, a tangential cut through the cingulate gyrus (1) just above the corpus callosum and near the roof of the lateral ventricle (2).

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Nolte’s The Human Brain in Photographs and Diagrams

A

Anterior cerebral artery Anterior choroidal artery Anterior inferior cerebellar artery Basilar artery Internal carotid artery (perforating branches) Middle cerebral artery Posterior cerebral artery Posterior inferior cerebellar artery Superior cerebellar artery Longitudinal fissure Anterior cerebral artery Optic chiasm Middle cerebral artery Superior temporal gyrus

Lateral sulcus

Posterior cerebral artery Amygdala

Middle temporal gyrus

Lateral ventricle (inferior horn)

Inferior temporal gyrus Collateral sulcus

Hippocampus

Occipitotemporal gyrus Basal pons

Parahippocampal gyrus Cerebellum:

Fourth ventricle

hemisphere vermis

Figure 6.4  (A) An axial section through the uncus and optic chiasm.

87

CHAPTER 6  Axial Sections

B

Gyrus rectus

Olfactory tract Hypothalamus

Optic chiasm

(tuberal region)

Periamygdaloid cortex

Third ventricle (infundibular recess)

Amygdala

Posterior cerebral artery

Hippocampus: hippocampus proper dentate gyrus subiculum

Posterior cerebral branches (penetrating branches)

Medial lemniscus

Oculomotor nerve (CN III)

Central tegmental tract

Middle cerebellar peduncle

Medial longitudinal fasciculus (MLF)

Trigeminal: motor nucleus main sensory nucleus

Trigeminal nerve fibers

Inferior cerebellar peduncle

Superior vestibular nucleus Figure 6.4 (Continued) (B) The central region of Fig. 6.4A, enlarged.

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A

Anterior cerebral artery Anterior choroidal artery Basilar artery Middle cerebral artery Middle cerebral artery (perforating branches) Posterior cerebral artery Posterior cerebral artery (perforating branches) Superior cerebellar artery

Subcallosal fasciculus Internal capsule

Longitudinal fissure Anterior cerebral branches Caudate nucleus

(anterior limb)

(head)

Lateral sulcus

Putamen

Insula

Superior temporal gyrus

Claustrum

Nucleus accumbens

Third ventricle

Optic tract

Middle cerebral branches

Amygdala

Anterior commissure

Hippocampus

Optic radiation

Middle temporal gyrus

Lateral ventricle (inferior horn)

Collateral sulcus

Interpeduncular fossa

Inferior temporal gyrus Occipitotemporal gyrus

Transverse fissure Fourth ventricle

Parahippocampal gyrus Cerebellum: hemisphere vermis

Figure 6.5  (A) An axial section through the base of the diencephalon.

CHAPTER 6  Axial Sections

B

Ventral amygdalofugal pathway Basal forebrain

Preoptic area

Lamina terminalis

Lenticulostriate arteries Anterior commissure

Hypothalamus: anterior region tuberal region posterior region

Mammillothalamic tract

Basal nucleus

Fornix

(of Meynert)

(column)

Mammillary body

Amygdala

Choroid plexus

Stria terminalis

Cerebral peduncle

Hippocampus:

Substantia nigra:

hippocampus proper dentate gyrus subiculum

reticular part compact part

Posterior cerebral branches

Medial lemniscus Spinothalamic tract

Oculomotor nerve fibers (CN III)

Lateral lemniscus

Decussation of the superior cerebellar peduncles

Central tegmental tract

Superior cerebellar peduncle

Medial longitudinal fasciculus (MLF)

Interposed nucleus Dentate nucleus Figure 6.5 (Continued) (B) The central region of Fig. 6.5A, enlarged.

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Nolte’s The Human Brain in Photographs and Diagrams

A

Anterior cerebral artery Anterior cerebral artery (perforating branches) Anterior choroidal artery Basilar artery Middle cerebral artery Middle cerebral artery (perforating branches) Posterior cerebral artery Posterior cerebral artery (perforating branches) Superior cerebellar artery Subcallosal fasciculus

Longitudinal fissure Anterior cerebral branches

Internal capsule

Corpus callosum (genu & rostrum)

(anterior limb)

Lateral ventricle (anterior horn)

Lateral sulcus

Subcallosal gyrus

Insula

Caudate nucleus (head)

Claustrum

Longitudinal fissure

Third ventricle

Putamen

Middle cerebral branch

Superior temporal gyrus

Anterior commissure

Optic tract

Optic radiation

Hippocampus Middle temporal gyrus

Lateral ventricle (inferior horn)

Collateral sulcus Inferior temporal gyrus

Red nucleus

Occipitotemporal gyrus

Transverse fissure Fourth ventricle

Parahippocampal gyrus Cerebellum: hemisphere vermis

Figure 6.6  (A) An axial section through all the deep cerebellar nuclei.

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CHAPTER 6  Axial Sections

B

Lamina terminalis

Globus pallidus

Preoptic area

Basal forebrain

Hypothalamus Ventral amygdalofugal pathway

Fornix (column)

Anterior commissure

Lenticulostriate arteries

Amygdala

Ansa lenticularis Mammillothalamic tract

Stria terminalis

Choroid plexus

Fimbria (fornix fibers)

Hippocampus: hippocampus proper

Posterior cerebral artery

dentate gyrus subiculum

Substantia nigra:

Cerebral peduncle

reticular part compact part

Red nucleus

Medial lemniscus

Decussation of the superior cerebellar peduncles

Spinothalamic tract Lateral lemniscus

Central tegmental tract

Fastigial nucleus

Medial longitudinal fasciculus (MLF)

Interposed nucleus

Superior cerebellar peduncle

Dentate nucleus Figure 6.6 (Continued) (B) The central region of Fig. 6.6A, enlarged.

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A

Anterior cerebral artery Anterior cerebral artery (perforating branches) Anterior choroidal artery Basilar artery Middle cerebral artery Middle cerebral artery (perforating branches) Posterior cerebral artery Posterior cerebral artery (perforating branches) Superior cerebellar artery Cingulate gyrus

Longitudinal fissure Corpus callosum

Lateral ventricle

(genu & rostrum)

(anterior horn)

Subcallosal gyrus

Subcallosal fasciculus

Caudate nucleus

Internal capsule:

(head)

anterior limb genu

Anterior commissure

Putamen

Insula

Fornix (column)

Claustrum

Globus pallidus:

Middle cerebral branches

external segment internal segment

Third ventricle

Internal capsule

Subthalamic nucleus

(posterior limb)

Caudate nucleus

Optic radiation

(tail)

Lateral ventricle

Red nucleus

(inferior horn)

Hippocampus

Collateral sulcus

Parahippocampal gyrus

Transverse fissure Cerebellum: hemisphere dentate nucleus vermis

Figure 6.7  (A) An axial section through the anterior commissure.

Occipitotemporal gyrus Cerebral aqueduct

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CHAPTER 6  Axial Sections

B

Longitudinal fissure

Anterior cerebral branches

Fornix (precommissural part)

Septal nuclei Hypothalamus

Anterior commissure Fornix

Ansa lenticularis + lenticular fasciculus

(column)

Inferior thalamic peduncle

Mammillothalamic tract

Subthalamic fasciculus

Habenulointerpeduncular tract Stria terminalis

Central tegmental tract

Fimbria

Optic tract

(fornix fibers)

Choroid plexus

Lateral geniculate nucleus

Hippocampus:

Posterior cerebral branches

hippocampus proper dentate gyrus subiculum

Medial lemniscus

Brachium of the inferior colliculus

Lateral lemniscus

Spinothalamic tract

Cerebellothalamic fibers

Oculomotor nucleus

Inferior colliculus

Figure 6.7 (Continued) (B) The central region of Fig. 6.7A, enlarged.

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A

Anterior cerebral artery Anterior cerebral artery (perforating branches) Anterior choroidal artery Middle cerebral artery Middle cerebral artery (perforating branches) Posterior cerebral artery Posterior cerebral artery (perforating branches) Superior cerebellar artery Cingulate gyrus Corpus callosum (genu)

Lateral ventricle (anterior horn)

Caudate nucleus (head)

Longitudinal fissure Subcallosal fasciculus Fornix (column)

Internal capsule:

Insula

anterior limb genu

Claustrum

Putamen

Third ventricle

Globus pallidus

Middle cerebral branch

(external segment)

Caudate nucleus

Internal capsule:

(tail)

posterior limb retrolenticular part

Optic radiation Collateral sulcus Occipitotemporal gyrus Transverse fissure Cerebellum: hemisphere vermis

Lateral ventricle (inferior horn)

Hippocampus Parahippocampal gyrus Cerebral aqueduct

Figure 6.8  (A) An axial section through the interventricular foramen and posterior commissure.

95

CHAPTER 6  Axial Sections

B

Septal vein

Anterior cerebral branches

Interventricular foramen

Septum pellucidum

(of Monro)

Septal nuclei Stria terminalis

Fornix (column)

Mammillothalamic tract

Terminal (thalamostriate) vein

Thalamic nuclei: CM, centromedian DM, dorsomedial LG, lateral geniculate MG, medial geniculate VA, ventral anterior VL, ventral lateral VPL, ventral posterolateral VPM, ventral posteromedial

Choroid plexus Interthalamic adhesion Reticular nucleus + external medullary lamina

VA

VL

Parafascicular nucleus DM

Stria terminalis

Habenulointerpeduncular tract

VPL

Fimbria (fornix fibers)

LG

Choroid plexus

V CM P M

MG

Pretectal area

Hippocampus:

Posterior commissure

hippocampus proper dentate gyrus subiculum

Periaqueductal gray

Posterior cerebral branch

Brachium of the inferior colliculus

Inferior colliculus

Superior colliculus

Figure 6.8 (Continued) (B) The central region of Fig. 6.8A, enlarged.

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A

Anterior cerebral artery Anterior choroidal artery Middle cerebral artery Middle cerebral artery (perforating branches) Posterior cerebral artery Posterior cerebral artery (perforating branches) Superior cerebellar artery Cingulate gyrus Corpus callosum

Longitudinal fissure

(genu)

Lateral ventricle

Subcallosal fasciculus

(anterior horn)

Fornix

Caudate nucleus

(body/column)

(head)

Internal capsule: anterior limb genu

Third ventricle Insula

Putamen

Claustrum

Lateral sulcus

Third ventricle

Globus pallidus (external segment)

Middle cerebral branch

Internal capsule:

Caudate nucleus

posterior limb retrolenticular part

(tail)

Optic radiation

Lateral ventricle (inferior horn)

Collateral sulcus Hippocampus Anterior calcarine sulcus

Parahippocampal gyrus

Transverse fissure Cerebellum: hemisphere vermis

Occipitotemporal gyrus Lingual gyrus Pineal gland Figure 6.9  (A) An axial section through the midthalamus.

97

CHAPTER 6  Axial Sections

B

Choroid plexus

Terminal (thalamostriate) vein

Anterior cerebral branches

Septum pellucidum Septal nuclei Stria terminalis

Fornix (column)

Transverse fissure

Thalamic nuclei: A, anterior CM, centromedian DM, dorsomedial Pul, pulvinar VA, ventral anterior VL, ventral lateral VPL, ventral posterolateral *, ventral posteromedial

Stria medullaris of the thalamus VA A VL

Reticular nucleus + external medullary lamina

DM VPL

Stria terminalis

*

Fimbria (fornix fibers)

Interthalamic adhesion

CM

Habenulointerpeduncular tract

Pul Pul

Habenula

Choroid plexus

Pretectal area

Hippocampus: hippocampus proper dentate gyrus subiculum

Superior colliculus

Posterior cerebral branch

Brachium of the superior colliculus

Pineal gland

Figure 6.9 (Continued) (B) The central region of Fig. 6.9A, enlarged.

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A

Anterior cerebral artery Anterior choroidal artery Middle cerebral artery Middle cerebral artery (perforating branches) Posterior cerebral artery Posterior cerebral artery (perforating branches) Superior cerebellar artery Cingulate gyrus Corpus callosum (genu/body)

Longitudinal fissure

Lateral ventricle

Subcallosal fasciculus

(anterior horn)

Fornix (body)

Caudate nucleus (head)

Internal capsule: anterior limb genu

Transverse fissure Insula

Putamen

Claustrum

Lateral sulcus Internal capsule

Middle cerebral branches

(posterior limb)

Caudate nucleus

Third ventricle

(tail)

Hippocampus

Optic radiation

Lateral ventricle

Collateral sulcus

(inferior horn)

Anterior calcarine sulcus

Cingulate gyrus (isthmus)

Transverse fissure Cerebellum: hemisphere vermis

Lingual gyrus Pineal gland

Figure 6.10  (A) An axial section at the level of the roof of the third ventricle.

99

CHAPTER 6  Axial Sections

B

Terminal (thalamostriate) vein

Choroid plexus

Anterior cerebral branches Septum pellucidum Fornix (body)

Transverse fissure

Stria terminalis

Internal cerebral vein Thalamic nuclei: A, anterior DM, dorsomedial Pul, pulvinar VA, ventral anterior VL, ventral lateral VPL, ventral posterolateral *, centromedian

VA

Stria medullaris

A

(of the thalamus)

VL Reticular nucleus + external medullary lamina

DM *

VPL Pul

Stria terminalis

Fimbria (fornix fibers)

Hippocampus:

Choroid plexus

hippocampus proper dentate gyrus subiculum

Pineal gland

Posterior cerebral branches

Figure 6.10 (Continued) (B) The central region of Fig. 6.10A, enlarged.

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A

Anterior cerebral artery Anterior choroidal artery Middle cerebral artery Middle cerebral artery (perforating branches) Posterior cerebral artery Posterior cerebral artery (perforating branches) Superior cerebellar artery Cingulate gyrus Corpus callosum (genu/body)

Lateral ventricle (anterior horn)

Longitudinal fissure Subcallosal fasciculus

Caudate nucleus

Fornix

(head)

(body)

Transverse fissure Caudate/putamen gray bridges

Middle cerebral branches

Lateral sulcus

Caudate nucleus (tail)

Corona radiata Optic radiation Lateral ventricle (inferior horn)

Collateral sulcus

Hippocampus

Anterior calcarine sulcus Transverse fissure Cerebellum: hemisphere vermis

Cingulate gyrus (isthmus)

Lingual gyrus

Figure 6.11  (A) An axial section through the transverse fissure and internal cerebral veins.

CHAPTER 6  Axial Sections

B

Terminal (thalamostriate) vein

Anterior cerebral branch

Choroid plexus Fornix (body)

Stria terminalis Transverse fissure

Thalamic nuclei: A, anterior LD, lateral dorsal LP, lateral posterior Pul, pulvinar VA, ventral anterior VL, ventral lateral *, dorsomedial

Reticular nucleus + external medullary lamina

VA VL LP

A LD

*

Pul

Stria terminalis Choroid plexus

Roof of the third ventricle Internal cerebral vein Fimbria (fornix fibers)

Hippocampus: hippocampus proper dentate gyrus subiculum

Posterior cerebral branches

Figure 6.11 (Continued) (B) The central region of Fig. 6.11A, enlarged.

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7  Sagittal Sections This chapter, the last of three showing sections of entire human brains, illustrates para sagittal planes. Forebrain structures continue to be emphasized, but parts of the brainstem and cerebellum are indicated as well. The organization of various functional systems in the forebrain (e.g., thalamus, hippocampus) is presented in Chapter 8. Colored diagrams showing typical areas of arterial supply in each section are provided in this and the preceding two chapters. We simplified these in two major ways. First, arterial territories are shown as sharply demarcated from each other when in reality there is significant interdigitation and overlap. Second, perforating arteries arise from all the vessels of the circle of Willis, but we lumped together those from the posterior communicating and posterior cerebral arteries and those from the anterior communicating and anterior cerebral arteries.

Caudate nucleus Putamen

Internal capsule

Hypothalamus Thalamus Amygdala Hippocampus

Figure 7.1  The axial sections from Figs. 6.3G and 6.3N, used in much of this chapter to indicate planes of section.

Third ventricle Lateral ventricle

Amygdala

Thalamus

7-7 7-8 7-9 7-10 7-11

Putamen

Caudate nucleus

Fourth ventricle 7-4 7-5 7-6

Hippocampus

Lateral ventricle

Third ventricle Hypothalamus Amygdala

Figure 7.2  The planes of section shown in this chapter, indicated on three-dimensional reconstructions. (Courtesy Dr. John W. Sundsten, Department of Biological Structure, University of Washington School of Medicine.)

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Figure 7.3  (A–P) Sixteen para sagittal sections of the right half of a brain. The sections are arranged in a lateral-to-medial sequence extending from the insula to the midline. Anterior is toward the left, so the view is as though you were backing through the brain, always looking from inside the brain out toward the lateral sulcus.

1

2

3

4 (A) The first section passes tangentially through the insula (5) and shows nicely how the lateral sulcus (6) leads to it and the circular sulcus (4) outlines it. The precentral (1) and postcentral (3) gyri can also be seen, separated from each other by the central sulcus (2), which, cut obliquely, seems deeper than it really is.

6

5

(B) The circular sulcus (1) is still present, partially surrounding the insula (2), but now the plane of section begins to reveal structures just deep to insular cortex—in this case the claustrum (3, 6). The most lateral part of the lateral ventricle, the inferior horn (5), also appears, with the tail of the caudate nucleus (4) cut tangentially in its wall.

2

3

1 4

5

6

1 2

3

A D H 5

(C) Now the putamen (1) appears and the claustrum (5), a sheet of gray matter that covers the curved lateral aspect of the putamen, appears to partially surround it in this two-dimensional view. The tail of the caudate nucleus (2) is cut tangentially in the wall of the inferior horn of the lateral ventricle (3). Across the ventricle, the hippocampus (4) makes its appearance. Shown enlarged in Fig. 7.4.

4

1

10

2

3

(D) The putamen (1) continues to increase in size, still partially surrounded by the claustrum (9). The tail of the caudate nucleus (2, 5) is now cut in two places as it curves into the temporal lobe with the inferior horn of the lateral ventricle (6). The posterior horn of the lateral ventricle (3) extends back toward the occipital lobe. The hippocampus (4) increases in size, and the amygdala (7) appears at its anterior end. A downward extension (8) of the putamen merges with the amygdala, much as the tail of the caudate nucleus merges with both in a nearby plane (see Fig. 7.3E). Fibers that have collected from the temporal lobe and will cross in the anterior commissure (10) mass underneath the putamen.

9 8 7 6

5

4

CHAPTER 7  Sagittal Sections

105

Figure 7.3 (Continued) Sagittal sections.

11

1

10

2

9 8

(E) The globus pallidus (1, part of its external segment) appears adjacent to the putamen (2), with fibers of the anterior commissure (3) traveling beneath them. The caudate nucleus is again cut twice, once (11) as it curves around from the body to the inferior horn of the lateral ventricle and a second time (4) as it merges with the amygdala (5). Fibers of the fimbria (7) are cut tangentially as they emerge from the hippocampus (6). An enlarged mass of choroid plexus (9, the glomus) protrudes into the atrium of the lateral ventricle (10), and the posterior horn of the ventricle (8) extends back into the occipital lobe. Shown enlarged in Fig. 7.5.

3 4 5 6

7

1

(F) Now both the internal (3) and external (2) segments of the globus pallidus can be seen adjacent to the putamen (1). The plane of section has reached the thalamus; the pulvinar (10) appears, as well as the lateral geniculate nucleus (6) with the optic tract (4) ending in it. The fimbria, cut tangentially in Fig. 7.3E, is now cut in two places (5, 8). The posterior horn of the lateral ventricle (7) appears in this plane to be a detached cavity in the occipital lobe but is in fact continuous with the atrium (9).

10 9

8 2 3

7

4 5

6

6

1 2

5 A D H 3 (G) The head of the caudate nucleus (2) appears, with fibers of the anterior limb of the internal capsule (1) emerging from the cleft between it and the putamen (3). Strands of gray matter (6) extend between the caudate nucleus and putamen, emphasizing the common embryological origin and similar pattern of connections of these two parts of the striatum. The most lateral of the deep cerebellar nuclei, the dentate nucleus (4), can be seen, and the parietooccipital sulcus (5) is now distinct. Shown enlarged in Fig. 7.6.

4 1

15 14

2

13 12

3 4 5

6

7 8

9

(H) The head of the caudate nucleus (2) is cut tangentially in the wall of the anterior horn of the lateral 11 ventricle (1). The continuity between the internal capsule (3, here the genu) and cerebral peduncle (6) is apparent. In the temporal lobe, the amygdala (4) and the anterior end of the hippocampus (5) underlie the uncus, and the fimbria is in the process of separating from the most caudal bit of hippocampus (13) and continuing as the crus of the fornix (14). The plane of section has moved deeper into the thalamus, and the medial geniculate nucleus (7), pulvinar (10), and nuclei of the lateral division (15, here the ventral posterolateral nucleus) can be seen. The dentate nucleus (9) is more fully formed, and visual cortex (11) occupies the banks 10 of the calcarine sulcus (12). The middle cerebellar peduncle (8) leaves the basal pons and enters the cerebellum. Illustration continued on following page

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Figure 7.3 (Continued) Sagittal sections.

1

2 3 4

(I) As the plane of section moves medially, progressively more of the prominent sulci of the medial surface of the brain become apparent—in this case the cingulate sulcus (1) and its marginal branch (2). The subthalamic nucleus (4) and substantia nigra (5) appear beneath the thalamus, and the continuous white-matter path from the internal capsule (3) through the cerebral peduncle (6) and into the basal pons (7) is shown nicely. The optic tract (8) proceeds posteriorly toward the lateral geniculate nucleus, and fibers of the anterior commissure (9) proceed toward (or away from) the midline.

5 6 7 9

8

(J) The subthalamic nucleus (3) and substantia nigra (4) are still apparent, and the centromedian nucleus (1) can now be seen in the thalamus. Fibers that formed the fimbria in previous sections of this series are now separated from the hippocampus and proceeding anteriorly as the crus of the fornix (2). The inferior cerebellar peduncle (5) turns dorsally and enters the cerebellum. The uncus (6) dwindles in size. Shown enlarged in Fig. 7.7.

1 2

3 4

6 5

17

16

1

15

2 3 4 5

I LP

6 (K) Many thalamic nuclei are now distinct, including the lateral dorsal (1), dorsomedial (2), centromedian (3), pulvinar (4), ventral anterior (15), ventral lateral (16), and anterior (17) nuclei. The olfactory tract (14) moves posteriorly across the orbital surface of the frontal lobe. As the plane of section approaches the midline, more brainstem components begin to become apparent, including the superior (7) and inferior (8) colliculi and the red nucleus (12), adjacent to the substantia nigra (11). The superior cerebellar peduncle (10) emerges from the cerebellum, and the interposed nucleus (9) largely replaces the dentate nucleus. Visual cortex (5) lines the calcarine sulcus (6). The last bit of the uncus (13), the cortex covering its medial surface, is present.

7 8 14

13

9

12 11

10 1 2 3 4

14 5

13 (L) Now the anterior nucleus (1) of the thalamus enlarges, with the mammillothalamic tract (3) ascending into it. The fornix is cut nearly tangentially through the crus (2). Fibers of the anterior commissure (13) continue on their course toward or away from the midline, and the right optic nerve (11) proceeds into the optic chiasm (10). Brainstem structures that can be seen more clearly or for the first time include the red nucleus (4), superior cerebellar peduncle (5), fourth ventricle (6), inferior olivary nucleus (7), and the pyramid (8) emerging from the basal pons (9). Nucleus accumbens (12) can be seen near the base of the forebrain, in continuity with the head of the caudate nucleus (14). Shown enlarged in Fig. 7.8.

6 12

11

10

7 9 8

CHAPTER 7  Sagittal Sections

107

Figure 7.3 (Continued) Sagittal sections.

2

16

1

15

3

14

4 13 5

(M) The fornix is cut twice (although nearly tangentially in each instance): through the crus and body (1), and as the column (4) ends in the mammillary body (7), from which the mammillothalamic tract (2) emanates. The physical continuity between the septal nuclei (3) and the hypothalamus (5) is apparent. The cingulate gyrus (16) narrows into an isthmus (13) through which it is continuous with the parahippocampal gyrus. Half the fibers from each optic nerve cross the midline in the optic chiasm (6), and the habenulointerpeduncular tract (14) descends from the habenula (15). Brainstem and cerebellar structures include the superior and inferior colliculi (12), periaqueductal gray (10), fastigial nucleus (11), and fibers of the superior cerebellar peduncle that emerge from their decussation (9) and pass through or around the red nucleus (8). Shown enlarged in Fig. 7.9.

12 6

7

11

8 9

10 (N) The plane of section, now very near the midline, passes through the body (1) and column (2) of the fornix as the latter travels just behind the anterior commissure (3). The hypothalamus (4), including the mammillary body (5) and emerging mammillothalamic fibers (7), forms the wall and floor of the third ventricle. Other near-midline structures include the basilar artery (6), pineal gland (8), and great cerebral vein of Galen (9). Shown enlarged in Fig. 7.10.

1

2

3

9 8

4 5

7 6

1

2

16

3

15 14

4

13 5

12 11 6 7

8

9 10

1

2

I LP (O) All the parts of the corpus callosum—the body (1), genu (4), rostrum (6), and splenium (14)—are now apparent. The septum pellucidum (3) merges with the septal nuclei (5), the fornix (2) is once again cut tangentially, and choroid plexus (7) passes through the interventricular foramen. The stria medullaris of the thalamus (15) proceeds posteriorly toward the habenula. Brainstem structures include the medial longitudinal fasciculus (11), the decussating superior cerebellar peduncles (10), and their continuation as cerebellothalamic fibers (8) surrounding the red nucleus (9). A continuous cleft of subarachnoid space, here made up of the transverse fissure (12, 16) and superior cistern (13), is interposed between the cerebral hemispheres and the rest of the brain.

11

3 10 4

9

5 6 7

8

(P) Almost exactly in the midline, an internal cerebral vein (1) travels posteriorly to join the great cerebral vein of Galen (10). Much of the ventricular system can also be seen, including the cerebral aqueduct (7) and the fourth ventricle (8). The section did not quite follow the entire septum pellucidum, and part of the anterior horn of the lateral ventricle (2) is visible through the resulting hole. The third ventricle (3) and its parts and boundaries are shown nicely: the lamina terminalis (4) at the rostral end of the ventricle, and the optic (5), infundibular (6), pineal (9), and suprapineal (11) recesses. Shown enlarged in Fig. 7.11.

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Nolte’s The Human Brain in Photographs and Diagrams

A

Putamen

Precentral gyrus

Central sulcus al Postcentral gyrus

Insula

Parietooccipital sulcus Caudate nucleus (tail)

Lateral ventricle

External capsule

(inferior horn)

Claustrum Collateral sulcus

Extreme capsule Middle cerebral branch

Cerebellum: primary fissure posterior lobe

Hippocampus Parahippocampal gyrus

Occipitotemporal (fusiform) gyrus

Figure 7.4  (A) A para sagittal section through lateral parts of the putamen and hippocampus.

109

CHAPTER 7  Sagittal Sections

B

Anterior choroidal artery Anterior inferior cerebellar artery Middle cerebral artery Middle cerebral artery (perforating branches) Posterior cerebral artery Posterior inferior cerebellar artery Superior cerebellar artery

Lenticulostriate arteries

Putamen

Alveus

Caudate nucleus (tail)

Hippocampus: hippocampus proper dentate gyrus

Figure 7.4 (Continued) (B) The central region of Fig. 7.4A, enlarged.

Choroid plexus

Lateral ventricle (inferior horn)

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Nolte’s The Human Brain in Photographs and Diagrams

A

Internal capsule (sublenticular part)

Precentral gyrus

Central sulcus Postcentral gyrus

Parietooccipital sulcus

Putamen

Caudate nucleus (body/tail)

Lateral ventricle:

Globus pallidus

atrium posterior horn

(external segment)

Middle cerebral branches Posterior cerebral branch

Claustrum Amygdala

Cerebellum: posterior lobe primary fissure anterior lobe posterior lobe

Hippocampus Parahippocampal gyrus

Occipitotemporal (fusiform) gyrus

Figure 7.5  (A) A para sagittal section passing longitudinally through much of the hippocampus.

111

CHAPTER 7  Sagittal Sections

B

Anterior cerebral artery Anterior choroidal artery Anterior inferior cerebellar artery Middle cerebral artery Middle cerebral artery (perforating branches) Posterior cerebral artery Posterior inferior cerebellar artery Superior cerebellar artery

Piriform cortex

Lenticulostriate arteries

Anterior commissure

Caudate nucleus (tail)

Stria terminalis

Caudate nucleus (body/tail)

Choroid plexus (glomus)

Fimbria (fornix fibers)

Hippocampus: hippocampus proper dentate gyrus

Amygdala

Lateral ventricle (inferior horn)

Hippocampus: hippocampus proper dentate gyrus

Choroid plexus

Subiculum

Choroid fissure

Figure 7.5 (Continued) (B) The central region of Fig. 7.5A, enlarged.

Fimbria (fornix fibers)

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Nolte’s The Human Brain in Photographs and Diagrams

A

Thalamus Internal capsule (posterior limb)

Precentral gyrus

Central sulcus Postcentral gyrus

Caudate nucleus (head)

Caudate nucleus (body/tail)

Putamen

Parietooccipital sulcus Posterior cerebral branches Globus pallidus:

Lateral ventricle:

external segment internal segment

posterior horn atrium

Claustrum

Hippocampus

Middle cerebral artery Amygdala

Cerebellum: Choroid fissure

Lateral ventricle (inferior horn)

Hippocampus Figure 7.6  (A) A para sagittal section through the amygdala and hippocampus.

posterior lobe primary fissure anterior lobe posterior lobe

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CHAPTER 7  Sagittal Sections

B

Ansa lenticularis

Optic tract

Anterior cerebral artery Anterior choroidal artery Anterior inferior cerebellar artery Middle cerebral artery Middle cerebral artery (perforating branches) Posterior cerebral artery Posterior cerebral artery (perforating branches) Posterior inferior cerebellar artery Superior cerebellar artery Caudate/putamen gray bridges

Reticular nucleus + external medullary lamina

Anterior commissure

Stria terminalis

Basal nucleus

Choroid plexus

(of Meynert)

(glomus)

Ventral amygdalofugal pathway

Fimbria (fornix fibers)

LP VPL

Lateral olfactory tract

Visual cortex Pul

LG

Lenticulostriate arteries

(stripe of Gennari)

Hippocampus: hippocampus proper dentate gyrus subiculum

Stria terminalis Amygdala

Parahippocampal gyrus

Choroid plexus

Fimbria (fornix fibers)

Hippocampus: hippocampus proper dentate gyrus subiculum

Thalamic nuclei: LG, lateral geniculate LP, lateral posterior Pul, pulvinar VPL, ventral posterolateral Figure 7.6 (Continued) (B) The central region of Fig. 7.6A, enlarged.

Dentate nucleus

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A

Thalamus

Lateral ventricle:

Choroid plexus

Central sulcus Cingulum

anterior horn, body

Cingulate sulcus (marginal branch)

Caudate nucleus (head)

Fornix (crus)

Internal capsule (genu)

Parietooccipital sulcus

Globus pallidus: external segment internal segment

Calcarine sulcus

Nucleus accumbens

Subthalamic nucleus

Ventral pallidum Basal forebrain

Cerebellum: posterior lobe primary fissure anterior lobe tonsil (part of the posterior lobe)

Optic tract Middle cerebral branch Uncus Posterior cerebral branch Inferior cerebellar peduncle Figure 7.7  (A) A para sagittal section through the uncus and the middle of the thalamus.

115

CHAPTER 7  Sagittal Sections

B

Stria terminalis

Anterior cerebral artery Anterior cerebral artery (perforating branches) Anterior choroidal artery Anterior inferior cerebellar artery Basilar artery Middle cerebral artery (perforating branches) Posterior cerebral artery Posterior cerebral artery (perforating branches) Posterior inferior cerebellar artery Superior cerebellar artery Reticular nucleus + external medullary lamina Terminal vein

Zona incerta

Superior brachium

Lenticular fasciculus

Visual cortex

(leaving globus pallidus)

(stripe of Gennari)

LD Anterior commissure

VA

VL VPL

Ansa lenticularis

*

CM

Basal nucleus

LP Pul MG

(of Meynert)

Inferior brachium

Dentate nucleus

Cerebellothalamic fibers

Cerebral peduncle

Posterior cerebral branch

Superior cerebellar branches

Lateral olfactory tract

Substantia nigra

Fornix (crus)

Thalamic nuclei: CM, centromedian LD, lateral dorsal LP, lateral posterior MG, medial geniculate Pul, pulvinar VA, ventral anterior VL, ventral lateral VPL, ventral posterolateral *, ventral posteromedial

Trigeminal main sensory nucleus Dorsal cochlear nucleus

Basal pons

Medial lemniscus, spinothalamic tract

Figure 7.7 (Continued) (B) The central region of Fig. 7.7A, enlarged.

Posterior inferior cerebellar branch

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Nolte’s The Human Brain in Photographs and Diagrams

A

Lateral ventricle

Thalamus

Choroid plexus

Fornix (crus)

Central sulcus

(body)

Cingulate sulcus

Cingulate gyrus

(marginal branch)

Subparietal sulcus

Lateral ventricle (anterior horn)

Parietooccipital sulcus

Corpus callosum (genu)

Caudate nucleus

Calcarine sulcus

(head)

Corpus callosum

Nucleus accumbens

(splenium)

Anterior cerebral artery

Cerebellum: posterior lobe primary fissure anterior lobe tonsil (part of the posterior lobe)

Optic nerve Optic chiasm Hypothalamus Red nucleus

Choroid plexus

Posterior cerebral artery Superior cerebellar peduncle Vertebral artery Figure 7.8  (A) A para sagittal section through the mammillothalamic tract.

Fourth ventricle

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CHAPTER 7  Sagittal Sections

B

Anterior cerebral artery Anterior cerebral artery (perforating branches) Anterior spinal artery Anterior inferior cerebellar artery Basilar artery Internal carotid artery (perforating branches) Posterior cerebral artery Posterior cerebral artery (perforating branches) Posterior inferior cerebellar artery Posterior spinal artery Superior cerebellar artery Vertebral artery Pallidothalamic fibers

Mammillothalamic tract

(ansa lenticularis + lenticular fasciculus)

Habenulointerpeduncular tract

Terminal vein

A

Stria terminalis

Cerebellothalamic fibers Pul

VA

Anterior commissure

VL CM/PF

Inferior colliculus Lateral lemniscus Mesencephalic tract (V)

Inferior thalamic peduncle

a t p

Preoptic area Mammillary body

LD

DM

Septal nuclei

Visual cortex (stripe of Gennari)

Superior cerebellar branches

Stria medullaris (of the thalamus)

Superior colliculus

Interposed nucleus Central tegmental tract

Substantia nigra:

Facial nerve

compact part reticular part

(internal genu)

Oculomotor nerve fibers

Abducens nucleus

Cerebral peduncle Thalamic nuclei: A, anterior CM/PF, centromedian & parafascicular DM, dorsomedial LD, lateral dorsal Pul, pulvinar VA, ventral anterior VL, ventral lateral

Medial lemniscus Trapezoid body Inferior olivary nucleus Pyramid Hypothalamus: Internal arcuate fibers a, anterior region Spinal tract (V) p, posterior region t, tuberal region

Figure 7.8 (Continued) (B) The central region of Fig. 7.8A, enlarged.

Vestibular nuclei Dorsal motor nucleus (X) Solitary tract & its nucleus Nucleus & fasciculus cuneatus

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Nolte’s The Human Brain in Photographs and Diagrams

A

Corpus C or callosum (body)

Fornix: body & crus

Thalamus

Central sulcus

Lateral ventricle (body)

Lateral ventricle (anterior horn)

Cingulate sulcus (marginal branch)

Choroid plexus

Subparietal sulcus Parietooccipital sulcus

Corpus callosum (genu)

Corpus callosum (splenium)

Anterior commissure

Calcarine sulcus Internal cerebral vein

Fornix

Pineal gland Cerebellum:

(column)

posterior lobe primary fissure anterior lobe tonsil (part of the posterior lobe)

Anterior cerebral artery Optic chiasm Hypothalamus Red nucleus Basilar artery Vertebral artery

Posterior inferior cerebellar branches

Fourth ventricle Figure 7.9  (A) A sagittal section through the column of the fornix as it enters the mammillary body.

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CHAPTER 7  Sagittal Sections

B

Anterior cerebral artery Anterior cerebral artery (perforating branches) Anterior spinal artery Anterior inferior cerebellar artery Basilar artery Internal carotid artery (perforating branches) Posterior cerebral artery Posterior cerebral artery (perforating branches) Posterior inferior cerebellar artery Posterior spinal artery Superior cerebellar artery Vertebral artery Habenulointerpeduncular tract

Habenula

Posterior commissure Superior colliculus

Stria medullaris (of the thalamus)

Cerebellothalamic fibers

A

Septal nuclei

DM Anterior commissure

Pul

VA PF

Mammillothalamic tract

Periaqueductal gray Inferior colliculus Lateral lemniscus

a

p

Trochlear decussation

t

Preoptic area Mammillary body

Fastigial nucleus

Oculomotor nerve

Central tegmental tract

Substantia nigra Superior cerebellar peduncles (decussation)

Abducens nucleus

Medial lemniscus

Vestibular nuclei

Trapezoid body Thalamic nuclei: A, anterior DM, dorsomedial PF, parafascicular Pul, pulvinar VA, ventral anterior

Solitary tract & its nucleus

Inferior olivary nucleus Hypothalamus: a, anterior region p, posterior region t, tuberal region

Nucleus & fasciculus gracilis Pyramid Internal arcuate fibers

Figure 7.9 (Continued) (B) The central region of Fig. 7.9A, enlarged.

Nucleus & fasciculus cuneatus

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Nolte’s The Human Brain in Photographs and Diagrams

A

Fornix: Corpus callosum

Thalamus

body & crus

Central sulcus

(body)

Callosomarginal artery Cingulate sulcus

Pericallosal artery

(marginal branch)

Anterior cerebral artery

Subparietal sulcus

Septum pellucidum Parietooccipital sulcus

Choroid plexus (in interventricular foramen)

Corpus callosum

Calcarine sulcus

(genu)

Fornix

Corpus callosum

(column)

(splenium)

Internal cerebral vein

Anterior commissure Anterior cerebral artery

Cerebellum: posterior lobe primary fissure anterior lobe tonsil (part of the posterior lobe)

Third ventricle (optic recess)

Optic chiasm Hypothalamus Red nucleus

Posterior inferior cerebellar branch

Basilar artery Fourth ventricle Figure 7.10  (A) A para sagittal section near the midline.

Median aperture

121

CHAPTER 7  Sagittal Sections

B

Anterior cerebral artery Anterior cerebral artery (perforating branches) Anterior spinal artery Anterior inferior cerebellar artery Basilar artery Internal carotid artery (perforating branches) Posterior cerebral artery Posterior cerebral artery (perforating branches) Posterior inferior cerebellar artery Posterior spinal artery Superior cerebellar artery Vertebral artery Mammillothalamic tract

Stria medullaris

Habenula

Pineal gland Posterior commissure

Septal nuclei Pul DM

A

Precommissural fornix

Cerebellothalamic fibers Oculomotor nucleus

Anterior commissure

a

t

Inferior colliculus

p

Trochlear nucleus Trochlear decussation

Preoptic area Mammillary body

Superior colliculus

Dorsal longitudinal fasciculus

Habenulointerpeduncular tract Oculomotor nerve fibers

Fastigial nucleus

Superior cerebellar peduncles (decussation) Thalamic nuclei: A, anterior DM, dorsomedial Pul, pulvinar Hypothalamus: a, anterior region p, posterior region t, tuberal region

Medial longitudinal fasciculus

Trapezoid body

Hypoglossal nucleus

Medial lemniscus

Area postrema

Inferior olivary nucleus Pyramid Internal arcuate fibers Pyramidal decussation Figure 7.10 (Continued) (B) The central region of Fig. 7.10A, enlarged.

Nucleus gracilis Nucleus cuneatus Fasciculus gracilis

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Nolte’s The Human Brain in Photographs and Diagrams

A

Corpus callosum

Fornix

(body)

Thalamus

(body)

Internal cerebral vein

Septum pellucidum Cingulate sulcus (marginal branch)

Lateral ventricle (anterior horn)

Corpus callosum

Corpus callosum

(splenium)

(genu)

Choroid plexus (in interventricular foramen)

Great cerebral vein (of Galen)

Subcallosal gyrus

Basal vein (of Rosenthal)

Anterior commissure Cerebellum:

Gyrus rectus

posterior lobe primary fissure anterior lobe posterior lobe nodulus

Optic chiasm Third ventricle Cerebral aqueduct Basilar artery Fourth ventricle

Median aperture

Figure 7.11  (A) A sagittal section almost exactly in the midline.

123

CHAPTER 7  Sagittal Sections

B

Anterior cerebral artery Anterior cerebral artery (perforating branches) Anterior spinal artery Anterior inferior cerebellar artery Basilar artery Internal carotid artery (perforating branches) Posterior cerebral artery Posterior cerebral artery (perforating branches) Posterior inferior cerebellar artery Posterior spinal artery Superior cerebellar artery Vertebral artery

Mammillothalamic tract

Thalamus (dorsomedial & midline nuclei)

Stria medullaris (of the thalamus)

Choroid plexus (in the roof of the third ventricle)

Third ventricle (suprapineal recess)

Habenular commissure Pineal gland Anterior commissure

Third ventricle (pineal recess)

Posterior commissure

Lamina terminalis

Inferior colliculus Third ventricle

Trochlear decussation

(optic recess)

Third ventricle (infundibular recess)

Tuber cinereum Mammillary body

Superior cerebellar peduncles (decussation) Trapezoid body Medial lemniscus

Area postrema

Pyramid Internal arcuate fibers Pyramidal decussation Figure 7.11 (Continued) (B) The central region of Fig. 7.11A, enlarged.

Fasciculus gracilis

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8  Functional Systems The preceding chapters presented the major structures seen at individual levels of the central nervous system (CNS) or in particular views of the brain. This chapter is complementary, using many of the same sections and views to indicate the structures and connections involved in particular neurological functions. We have taken a “bare-bones” approach to this task and indicated only major pathways and connections. Much of the circuitry discussed in standard textbooks has been omitted in the interest of simplicity. The locations of neuronal cell bodies, the trajectories of their axons in tracts, and the locations of their synaptic endings are usually indicated by cartoon neurons like this one: Neuronal cell body

Axon Synaptic ending

In addition, some anatomical liberties were taken to keep the diagrams relatively simple. The number of lines was minimized by indicating axons as diverging or converging:

• Fig. 8.12. Voluntary movement of muscles of the head and neck: the corticobulbar tract

VISCERAL AFFERENTS AND EFFERENTS • Fig. 8.13. Visceral and gustatory afferents, preganglionic sympathetic and parasympathetic neurons

BASAL GANGLIA • Fig. 8.14. The major circuit of the basal ganglia • Fig. 8.15. Connections of the striatum (caudate nucleus, putamen, nucleus accumbens) • Fig. 8.16. Connections of the globus pallidus • Fig. 8.17. Connections of the substantia nigra • Fig. 8.18. Connections of the subthalamic nucleus

CEREBELLUM (Axons frequently branch to innervate multiple targets, but this is not what we mean to indicate in any of these figures; moreover, axons from multiple neurons never converge to form a single axon.) Finally, colors were used to make it easier to follow particular pathways in each figure. Their use is consistent within a given figure but not across figures: We were unable to devise a meaningful color scheme that would accommodate all the different functional systems. Hence a given color seldom has a functional implication.

LONG TRACTS OF THE SPINAL CORD AND BRAINSTEM • Fig. 8.1. Touch sensation and proprioception: the posterior column–medial lemniscus system • Fig. 8.2. Pain and temperature sensation: the anterolateral system • Fig. 8.3. Voluntary movement: the corticospinal tract

SENSORY SYSTEMS OF THE BRAINSTEM AND CEREBRUM • • • • • •

Fig. Fig. Fig. Fig. Fig. Fig.

8.4. 8.5. 8.6. 8.7. 8.8. 8.9.

Connections of the trigeminal nerve Chemical senses: gustatory system Chemical senses: olfactory system Connections of the eighth nerve: auditory system Connections of the eighth nerve: vestibular system Visual system and visual fields

CRANIAL NERVE MOTOR NUCLEI • Fig. 8.10. Cranial nerve nuclei that innervate ordinary skeletal muscle (via cranial nerves III, IV, VI, and XII) • Fig. 8.11. Cranial nerve nuclei that innervate muscles of branchial arch origin (via cranial nerves V, VII, IX, X, and XI)

• Fig. 8.19. Gross anatomy • Fig. 8.20. Cerebellar circuitry: afferent and efferent routes through the cerebellar peduncles • Fig. 8.21. Cerebellar circuitry: structure of cerebellar cortex • Fig. 8.22. Inputs to the cerebellum • Fig. 8.23. Outputs from the cerebellum to the forebrain • Fig. 8.24. Outputs from the cerebellum to the brainstem

THALAMUS AND CEREBRAL CORTEX • Fig. 8.25. Projections of thalamic relay nuclei to the cerebral cortex • Fig. 8.26. Projections of thalamic association nuclei to the cerebral cortex • Fig. 8.27. Internal capsule

HYPOTHALAMUS AND LIMBIC SYSTEM • Figs. 8.28 and 8.29. Connections of the hypothalamus • Fig. 8.30. An overview of the limbic system • Figs. 8.31 and 8.32. Major input/output pathways of the limbic system • Fig. 8.33. Inputs to the amygdala • Fig. 8.34. Outputs from the amygdala • Fig. 8.35. Inputs to the hippocampus • Fig. 8.36. Outputs from the hippocampus

CHEMICALLY CODED NEURONAL SYSTEMS • • • • •

Fig. Fig. Fig. Fig. Fig.

8.37. 8.38. 8.39. 8.40. 8.41.

Cholinergic neurons and pathways Noradrenergic neurons and pathways Dopaminergic neurons and pathways Serotonergic neurons and pathways Modulatory outputs from the hypothalamus 125

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Nolte’s The Human Brain in Photographs and Diagrams

Figure 8.1  (A) The posterior column–medial lemniscus system.

Large-diameter primary afferent fibers, conveying information about limb position and movement and the details of tactile stimuli, enter the spinal cord in the medial division of each dorsal rootlet (Fig. 8.1B [inset 1]). The principal route through which this information reaches consciousness is the posterior column–medial lemniscus pathway. Branches of the primary afferents ascend through the ipsilateral posterior funiculus (posterior column). Entering fibers add onto the lateral aspect of fibers already present in the posterior funiculus (Fig. 8.1B [inset 2]), so by the time they reach the medulla, fibers conveying information from the leg are located in the more medial fasciculus gracilis and those conveying information from the arm in the more lateral fasciculus cuneatus. This is the beginning of a somatotopic arrangement that is maintained (with some twists and turns) throughout the remainder of this pathway. Each posterior column terminates in the ipsilateral posterior column nuclei (nuclei gracilis and cuneatus), whose axons cross the midline and ascend to the ventral posterolateral nucleus (VPL) of the thalamus. VPL in turn projects to primary somatosensory cortex in the postcentral gyrus. An analogous pathway conveying similar information from the face involves primary afferents with cell bodies in the trigeminal ganglion and the mesencephalic nucleus of the trigeminal nerve (see Fig. 8.4). Central processes of these afferents terminate in the main sensory nucleus of the trigeminal nerve. Their axons cross the midline, join the somatotopically appropriate region of the medial lemniscus, and ascend to the ventral posteromedial nucleus (VPM) of the thalamus. VPM in turn projects to the face area of the postcentral gyrus. Tactile and proprioceptive information can also reach consciousness by way of postsynaptic fibers arising from spinal cord neurons. Some of these projections travel in the posterior columns, but others travel in pathways outside the posterior funiculus (e.g., tactile information in the anterolateral system described in Fig. 8.2), so posterior column damage does not cause total loss of touch and position sensation.

CHAPTER 8  Functional Systems Figure 8.1 (Continued) (B) The posterior column–medial lemniscus system, continued. (Inset 2 redrawn from Mettler FA. Neuroanatomy. 2nd ed. St Louis: Mosby; 1948.)

Somatosensory So mat cortex (postcentral (po ostce gyrus)

Internal capsule (posterior limb)

VPL VPM

Large fiber entry zone

Mesencephalic ncephalic cleus of V nucleus Main sensory nucleus of V Medial lemniscus Trigeminal al ganglion n Nucleus gracilis Nucleus leus cuneatus

Medial lemniscus Dorsal root oot ganglia (levels els above T6)

Fasciculus ciculus cuneatus

Fasciculus gracilis

Dorsal root ganglia (levels below T6)

Fasciculus F i l gracilis ili

Fasciculus gracilis

Fasciculus cuneatus

127

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Nolte’s The Human Brain in Photographs and Diagrams

Figure 8.2  (A) The anterolateral system.

Small-diameter afferent fibers conveying pain and temperature (and a limited amount of tactile) information enter the spinal cord in the lateral division of each dorsal rootlet. The principal route through which this information reaches consciousness is the spinothalamic tract. Primary afferents terminate on tract cells in the posterior horn, whose axons cross and join the spinothalamic tract, adding onto the ventromedial aspect of fibers already present. This is the beginning of a somatotopic arrangement that is maintained (relatively unchanged) throughout the pathway. Spinothalamic fibers then ascend to VPL of the thalamus, which projects to primary somatosensory cortex in the postcentral gyrus. The analogous pathway dealing with the face involves trigeminal ganglion cells whose central processes descend through the spinal trigeminal tract to caudal parts of the spinal trigeminal nucleus (see Fig. 8.4). Axons of these second-order neurons cross the midline, join the somatotopically appropriate region of the spinothalamic tract, and ascend to VPM of the thalamus. VPM in turn projects to the face area of the postcentral gyrus. Pain and temperature information is in fact more widely distributed than this simplified account would indicate and reaches the reticular formation, additional thalamic nuclei, and multiple cortical areas. Several additional pain pathways travel with or near the spinothalamic tract, and all are commonly referred to collectively as the anterolateral system. Access to the spinothalamic tract is modulated by small neurons of the substantia gelatinosa (and at several other sites). One important pain-control pathway originates in the periaqueductal gray matter of the midbrain and involves a relay in the raphe nuclei (see Fig. 8.40) and nearby reticular formation of the medulla and caudal pons. The periaqueductal gray sums up anterolateral and limbic inputs to help determine when to turn this pathway on.

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Figure 8.2 (Continued) (B) The anterolateral system, continued.

Postcentral gyrus Pos Postcen ( (other co cortical areas also pain and temperature receive p informat information)

Internal capsule s in other Endings m nuclei mic thalamic

VPL

(posterior limb)

M VPM

u us, From hypothalamus, yg , cortex e ex amygdala,

Periaqueductal ctal gray gra ray Anterolateral system An Anterolateral

Descending pain control

((sp (spinothalamic i th l i + other th ttracts) t )

RF R F Anterolateral system Trigeminal ganglion

Raphe R h nuclei

(spinothalamic + other tracts)

RF=endings in the reticular formation Spinal trigeminal tract & nucleus RF

Dorsal root ganglia

Lissauer’s tract Sub Substantia gela gelatinosa

Anterolateral system A (spinothalamic + other tracts)

From the raphe nuclei

Substantia gelatinosa interneuron

Spinothalamic tract cells

Anterolateral system (spinothalamic + other tracts)

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Figure 8.3  (A) The corticospinal tract.

Commands for the initiation of voluntary movements are conveyed to the spinal cord via the corticospinal tract, which includes not only fibers originating in primary motor cortex of the precentral gyrus but also fibers originating in premotor, supplementary motor (not shown), and somatosensory cortex. Corticospinal axons descend through the internal capsule, cerebral peduncle, and basal pons in company with corticopontine and corticobulbar fibers. They then continue into the pyramids of the medulla. At the spinomedullary junction, most corticospinal fibers decussate (see inset below) to form the lateral corticospinal tract. Those that do not cross in the pyramidal decussation continue into the smaller anterior corticospinal tract and typically cross in the spinal cord before terminating. Finally, the axons originating in motor areas of the cortex terminate on motor neurons (or, more often, on nearby interneurons); those originating in somatosensory cortex terminate in the posterior column nuclei and posterior horn and presumably play a role in modulating the transmission of sensory information.

Cerebral peduncle Ce

Basal pons

Pyramid

Pyramidal decus ss sation decussation

Lateral corticospinal trac tract ct

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Figure 8.3 (Continued) (B) The corticospinal tract, continued.

Premotor cortex (many corticospinal fibers originate here)

Primary motor cortex Internal capsule (posterior limb)

Cerebral peduncle

Corticospinal tract Co (dispersed in the basal pons)

Pyramid Pyr dal decussation Pyramidal Lateral corticospinal tract

Anterior horn rn n motor neurons s Ventral root ot

Anterior corticospinal tract

Somatosensory cortex (many corticospinal fibers originate here)

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Figure 8.4  (A) Central connections of the trigeminal nerve.

The trigeminal nerve conveys somatic sensory information from most of the head, and it is also the motor nerve for most muscles of mastication. Connections of the trigeminal motor nucleus are noted in Fig. 8.11, and sensory connections are reviewed here. The connections of somatosensory components bear many similarities to those of spinal nerves (see Figs. 8.1 and 8.2), but there are important differences as well. Large-diameter trigeminal afferents have cell bodies in the trigeminal ganglion or in the mesencephalic nucleus of the trigeminal (in effect, a bit of the trigeminal ganglion located within the CNS instead of in the periphery). Many central processes terminate in the main sensory nucleus of the trigeminal, which in turn projects through the contralateral medial lemniscus to VPM of the thalamus. (Part of the main sensory nucleus, where the mouth is represented, sends an uncrossed projection, the dorsal trigeminal tract, to the ipsilateral VPM; the functional significance of this uncrossed projection is unclear.) Other central processes project to the trigeminal motor nucleus as part of the masseter stretch reflex arc, or to trigeminocerebellar neurons in rostral parts of the spinal trigeminal nucleus. Small-diameter trigeminal afferents, all with cell bodies in the trigeminal ganglion, travel through the spinal trigeminal tract to termination sites at various levels of the spinal trigeminal nucleus. The most caudal levels of the spinal trigeminal tract and nucleus are essentially rostral extensions of Lissauer’s tract and the posterior horn, respectively, of the upper cervical spinal cord and have an analogous function. That is, they convey information about facial pain and temperature to VPM. This seemingly odd location of the second-order neurons for facial pain and temperature ensures that, moving from the spinal cord into the brainstem, there is a smooth continuation of the somatotopic pain/temperature map. More rostral levels participate in trigeminocerebellar projections and in other reflexes, notably the bilateral blink reflex in response to an object touching either cornea.

CHAPTER 8  Functional Systems Figure 8.4 (Continued) (B) Central connections of the trigeminal nerve, continued.

Internal capsule (posterior limb)

Somatosensory cortex Somat (postce (postcentral gyrus)

Mesencephalic nucleus of V

Dorsal trig ge em min ina all tract

VPM

in sensory Main ucleus of V nucleus

Trigeminal motor nucleus

Anterolateral system (spinothalamic + other tracts)

Medial M di l llemniscus i

igeminal Trigeminal g ganglion

VII = endings in the facial motor nucleus (part of the blink reflex arc)

Spinal trigeminal tract & nucleus VII V VII VII V

Anterolateral system (spinothalamic + other tracts)

Spinal trigeminall tractt & nucleus s

Anterolateral system (spinothalamic + other tracts)

Lissauer’s tract ng The most caudally projecting ch trigeminal afferents reach the upper cervical spinal cord rd

Substantia gelatinosa Anterolateral system (spinothalamic + other tracts)

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Figure 8.5  (A) Central gustatory connections.

What we commonly refer to as “taste” is actually a complex sensation. Sensory information from taste buds is an important contributor, but this is combined with information from olfactory receptors (aroma) and trigeminal endings (texture, spiciness, temperature). To avoid ambiguity the sensations initiated in taste buds are referred to as gustatory sensations. Receptor cells in taste buds synapse on peripheral processes of fibers in the facial (VII), glossopharyngeal (IX), and vagus (X) nerves. Facial endings innervate taste buds on the anterior two thirds of the tongue, glossopharyngeal endings innervate those on the posterior third, and vagal endings innervate scattered taste buds of the epiglottis and esophagus. Central processes of these gustatory primary afferents travel through the solitary tract to reach second-order neurons in rostral parts of the nucleus of the solitary tract. Second-order gustatory neurons influence feeding-related behavior and autonomic functions by projecting to the dorsal motor nucleus of the vagus, to the nearby reticular formation, and even to preganglionic sympathetic neurons in the spinal cord (not indicated in the accompanying figures). Conscious perception of taste is mediated by a largely uncrossed projection from the nucleus of the solitary tract to the thalamus (VPM), and from there to the gustatory cortex in the insula and the adjacent frontal operculum. Gustatory information also reaches the hypothalamus and amygdala, where it influences metabolic regulation and feelings of hunger, satiety, and pleasantness or unpleasantness accompanying various tastes. The route utilized involves, at least partially, a projection from gustatory cortex to the amygdala. In many animals, gustatory information is also transmitted to the hypothalamus and amygdala more directly, through a projection from the parabrachial nuclei of the pontine reticular formation. Whether this pathway exists in humans is doubtful, as implied by question marks in Fig. 8.5B.

CHAPTER 8  Functional Systems Figure 8.5 (Continued) (B) Central gustatory connections, continued.

Gustatory cortex (insula, frontal operculum)

capsule Internal caps (posterior limb limb)

Hypothalamus

VPM

? ala Amygdala

?

?

Parabrachial nuclei

Central tegmental ttract

g Geniculate g ganglion CN V VII II

Solitary tract & its nucleus

Inferior ganglion of IX CN IX CN X

Inferior ganglion of X

R Reticular formation

Dorsal motor nucleus of the vagus

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Figure 8.6  (A) Central olfactory connections.

The olfactory bulb develops as an outgrowth of the cerebral hemisphere, leading to a unique arrangement of connections in the olfactory system. The axons of olfactory receptor neurons, collectively making up cranial nerve I, pass through the cribriform plate of the ethmoid bone and terminate in the olfactory bulb. Second-order olfactory neurons then project through the olfactory tract to a variety of nearby sites, all part of the ipsilateral cerebral hemisphere. Some olfactory tract fibers terminate in the anterior olfactory nucleus (which in turn projects through the anterior commissure to the contralateral olfactory bulb) or the olfactory tubercle (an inconspicuous part of the anterior perforated substance at the base of the cerebrum). The remaining fibers curve toward the temporal lobe as the lateral olfactory tract to reach olfactory cortical areas (piriform cortex adjacent to the lateral olfactory tract, periamygdaloid cortex overlying part of the amygdala, and entorhinal cortex at the anterior end of the parahippocampal gyrus) and a restricted part of the amygdala. This is the only known example of sensory information reaching the cerebral cortex directly, without a stop in the thalamus. Olfactory information is subsequently distributed more widely, both by projections from these primary olfactory receiving areas and by relays in the thalamus. Some of these olfactory projections converge with gustatory and somatosensory information in an area of orbital cortex important for integrated judgments of flavor.

CHAPTER 8  Functional Systems Figure 8.6 (Continued) (B) Central olfactory connections, continued.

From olfactory bulb

Olfactory tract O

Periamygdaloid cortex

Olfactory tract (and adjacent anterior olfactory nucleus)

Olfactory y epithelium Olfactory nerve (CN I)

Amygdala Olfactory bulb O

Olfactory bulb

Olfactory tract

Anterior olfactory nucleus

O Olfactory tract

Lateral olfactory tract Piriform cortex

Anterior commissure c

Olfactory tubercle Amygdala

Piriform cortex Lateral olfactory tract

Amygdala

Entorhinal cortex

Periamygdaloid cortex Entorhinal cortex

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Figure 8.7  (A) The auditory system.

Auditory information reaches the brainstem via the cochlear division of cranial nerve VIII, a collection of primary afferent fibers with cell bodies in the spiral ganglion (embedded in the cochlea), peripheral processes that innervate cochlear hair cells, and central processes that terminate in the dorsal and ventral cochlear nuclei at the pontomedullary junction. In contrast to the somatosensory system, the second-order neurons of the cochlear nuclei project bilaterally (crossing fibers in the trapezoid body) to higher levels of the auditory system, allowing for sound localization by comparing inputs from the two ears. The first site where such binaural comparisons occur is the superior olivary nucleus. Efferents from each superior olivary nucleus, together with crossed and uncrossed projections from the cochlear nuclei, ascend to the inferior colliculus through the lateral lemniscus. The inferior colliculus then projects through the brachium of the inferior colliculus to the medial geniculate nucleus of the thalamus, which in turn projects to auditory cortex in the temporal lobe. Primary auditory cortex is located in the aptly named transverse temporal gyri (of Heschl) on the superior surface of the superior temporal gyrus. One consequence of this bilateral representation of each ear at all levels beyond the cochlear nuclei is that serious hearing loss restricted to one ear implies damage at the level of the cochlear nuclei or (more likely) the middle or inner ear or the eighth nerve.

CHAPTER 8  Functional Systems Figure 8.7 (Continued) (B) The auditory system, continued.

Auditory cortex (transverse temporal gyri, on the superior surface of the temporal lobe)

Auditory cortex (transverse temporal gyri, on the superior surface of the temp temporal lobe)

Medial geniculate nucleus Internal capsule

Internal capsule

(sublenticular part)

(sublenticular part)

Inferior colliculus Lateral lemniscus

Lateral lemniscus

(ending in the inferior colliculus)

(ending in the inferior colliculus)

Lateral lemniscus s

L lemni Lateral lemniscus

Superior olivary nucleus

Transverse temporal gyri

Trapezoid body

Dorsal & ventral cochlear nuclei

Cranial nerve VIII C (cochlear division) (c

Spiral ganglion

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Figure 8.8  (A) The vestibular system.

Vestibular information reaches the brainstem via the vestibular division of cranial nerve VIII, a collection of primary afferent fibers with cell bodies in the vestibular ganglion, peripheral processes that innervate hair cells in the utricle, saccule, and semicircular ducts, and central processes that mostly terminate in the vestibular nuclei of the rostral medulla and caudal pons. The vestibular nuclei then project to the spinal cord (to mediate postural responses to linear and angular acceleration, and to coordinate head movements with eye movements) and to the abducens, trochlear (not shown), and oculomotor nuclei (to mediate eye movements compensating for head movements—the vestibuloocular reflex).

Abundant interconnections between the vestibular nuclei and the cerebellum (particularly the flocculonodular lobe and parts of the vermis) assist in these tasks, aided by some vestibular primary afferents projecting directly to the cerebellum. Finally, there is a projection (not shown) from the vestibular nuclei to the thalamus through which changes in head position or motion reach consciousness. The lateral and medial vestibulospinal tracts arise primarily from the lateral and medial vestibular nuclei respectively. Other vestibular connections, however, are shared among all the nuclei; the apparently exclusive connections in Fig. 8.8B are merely a mechanism for minimizing the number of lines in the figure.

CHAPTER 8  Functional Systems Figure 8.8 (Continued) (B) The vestibular system, continued.

Oculomotor nucleus

Medial longitudinal fasciculus (MLF)

Superior vestibular nucleus

(not the only route taken by these fibers)

Lateral vestibular nucleus Abducens nucleus Nodulus

cle un d e rp

lla be e r ce ior r fe

Inferior Inf ferior & superior vestibular ve estibular nuclei Medial vestibular nucleus cleus

In

Medial longitudinal fasciculus (MLF) Cranial nerve V VIII ((vestibular vestibular divisio division) on) o

r rio fe In b cere rp ella

u ed

nc

le

Flocculus

Medial vestibulospinal tract (only to cervical levels)

Lateral vestibulospinal tract (to all levels)

Lateral vestibulospinal tract (to all levels)

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Figure 8.9  (A) The visual system.

The part seen by both right and left eyes

The part seen by the right eye only

3. The visual field of the right eye.

Seen only by the right eye

Field of the left eye

R

L

Field of the right eye

Seen only by the right eye Peripheral vision (both eyes)

Lower vertical midline

Central vision

Upper vertical midline 1. The map of the right visual field (of both eyes) in primary visual cortex of the left occipital lobe. The foveal representation is most posterior and extends over the occipital pole. (Most visual cortex is actually in the walls of the calcarine sulcus.)

2. The visual pathway, shown over a dissection of the ventral surface of the brain. (Modified from Ludwig E, Klingler J: Atlas cerebri humani. Boston: Little, Brown & Co.; 1956.)

4. The central connections of the right optic nerve (only foveal fibers shown).

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Figure 8.9 (Continued) (B) The visual system.

Field of the left eye

Field of the right eye Field of the left eye

Field of the right eye

line

Binocular periphery

Uppe

lm

L ow er

ve r

tic al

mi d

Monocular periphery

r ve r t i c

Optic chiasm damage causes heteronymous deficits

Optic nerve damage causes a monocular deficit

(here bitemporal hemianopia)

e lin id

a

Right CN II Central 5˚ (continues onto lateral surface)

Right optic tract damage: left homonymous hemianopia Optic tract

Optic radiation damage: homonymous, but less than hemianopia Ganglion cells in right temporal and nasal retina

Lateral geniculate nucleus

(e.g., in this case superior quadrantanopia following damage to fibers curving through the temporal lobe before turning posteriorly)

Internal capsule (sublenticular & retrolenticular parts)

Optic: nerve chiasm tract

O Optic radiation L Lower quadrants in the upper ban nk bank

Lateral geniculate nucleus

Optic Op radiation Upper quadrants in the lower bank

Brachium of the superior colliculus

Right visual cortex damage: left homonymous hemianopia

Optic radiation

(often with macular sparing)

Visual cortex

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Figure 8.10  Cranial nerve nuclei that innervate ordinary skeletal muscle.

Oculomotor nucleus

Oculomotor nerve (CN III), to: inferior oblique inferior rectus levator palpebrae superioris medial rectus superior rectus (and other components shown in Fig. 8.13)

Trochlear nucleus

Trochlear nerve (CN IV), to superior oblique

Medial longitudinal fasciculus (MLF)

Abducens nucleus

Abducens nerve (CN VI), to lateral rectus

Hypoglossal nucleus

Hypoglossal nerve (CN XII), to tongue muscles

Cranial nerve motor nuclei for ordinary skeletal muscle are typically located near the floor of the ventricular system and near the midline (see Figs. 3.3, 3.4, and 3.6). The axons of these motor neurons leave the brainstem in cranial nerves III, IV, VI, and XII. Some of these axons—specifically, those for the superior oblique (CN IV) and superior rectus (CN III)—cross the midline before they exit. This is an unusual situation because motor neurons generally innervate ipsilateral muscles. It is presumed to be an adaptation to maintain certain interrelationships between head movements and eye movements (e.g., all the motor neurons needed to rotate both eyes in the same direction are located on the same side of the brainstem). The abducens nucleus contains not only the motor neurons for the ipsilateral lateral rectus, but also a population of interneurons whose axons cross the midline and ascend through the medial longitudinal fasciculus (MLF) to medial rectus motor neurons. Simultaneous activation of both populations of neurons in the abducens nucleus thus results in conjugate gaze to the ipsilateral side.

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Figure 8.11  Cranial nerve nuclei that innervate skeletal muscle of branchial arch origin.

Trigeminal motor nucleus

Trigeminal nerve (CN V, motor root) to: muscles of mastication (masseter, temporalis, pterygoids, others); tensor tympani

Facial nerve (CN VII) to: buccinator, orbicularis oris, orbicularis oculi, other facial muscles; stapedius

Internal genu of the facial nerve

Facial motor nucleus

(see Fig. 8.13 for other components)

Glossopharyngeal nerve (CN IX), to stylopharyngeus (see Fig. 8.13 for other components)

Vagus nerve (CN X), to laryngeal and pharyngeal muscles (see Fig. 8.13 for other components)

Nucleus ambiguus (extends longitudinally through the rostral medulla)

Accessory nerve (CN XI), to: sternocleidomastoid trapezius Accessory nucleus (extends longitudinally from the caudal medulla through C5)

Cranial nerve motor nuclei for skeletal muscle derived embryologically from branchial arches are typically located farther from both the midline and the floor of the ventricular system than are their counterparts for ordinary skeletal muscle (see Figs. 3.3, 3.4, and 3.6). The axons of these motor neurons leave the brainstem in cranial nerves V, VII, IX, X, and XI. Many of them make an odd, hairpin turn before their exit. Axons leaving the facial motor nucleus provide the most striking example, hooking around the abducens nucleus in an internal genu (accounting for the facial colliculus in the floor of the fourth ventricle—see Fig. 1.11A).

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Figure 8.12  (A) The corticobulbar tract.

Commands for the initiation of voluntary movements mediated by cranial nerves are conveyed to the brainstem via the corticobulbar tract, which includes not only fibers originating in primary motor cortex of the precentral gyrus but also fibers originating in premotor, supplementary motor (not shown), and somatosensory cortex. Corticobulbar axons descend through the internal capsule, cerebral peduncle, basal pons, and medullary pyramids in company with corticopontine and corticospinal fibers. At the levels of the motor nuclei of cranial nerves V, VII, IX, X, XI, and XII, contingents of these fibers peel off and terminate on motor neurons there (or, more often, on nearby interneurons). In contrast to the corticospinal tract, which mostly crosses in the pyramidal decussation, the corticobulbar fibers from each hemisphere are distributed bilaterally. This corresponds to the way in which muscles on both sides of the face and head are typically used simultaneously (e.g., chewing, swallowing, speaking). As a result of this bilateral distribution, unilateral damage to the internal capsule or corticobulbar tract typically does not cause substantial, lasting weakness of these muscles. The major exception is the muscles of the lower face, whose motor neurons receive a predominantly crossed corticobulbar input (corresponding to the way in which we can make asymmetrical lower facial expressions). Hence, weakness of one lower quadrant of the face is an important clinical sign of contralateral corticobulbar damage. (The nuclei of cranial nerves III, IV, and VI receive no direct corticobulbar inputs, because cortical projections instead reach brainstem pattern generators that in turn drive coordinated movements of the two eyes.)

CHAPTER 8  Functional Systems Figure 8.12 (Continued) (B) The corticobulbar tract, continued.

Premotor cortex (many corticobulbar fibers originate here)

Trigeminal motor nucleus

Primary motor cortex CN V

CN VII (to upper face)

Facial motor nucleus

CN VII (to lower face)

CN IX, X Nucleus ambiguus Pyramid Pyra

Pyramidal midal decussation

Lateral corticospinal tract

CN XI Accessory nucleus

Somatosensory cortex (many corticobulbar fibers originate here)

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Figure 8.13  (A) Visceral and gustatory afferents (right side of the figure); preganglionic sympathetic and parasympathetic neurons (left side of the figure). Relatively minor elements (e.g., visceral afferents in the facial nerve) and some elements lacking a distinct CNS nucleus (e.g., preganglionic parasympathetics mediating lacrimation and salivation via the facial and glossopharyngeal nerves) have been omitted.

CHAPTER 8  Functional Systems Figure 8.13 (Continued) (B) Visceral afferents and efferents, continued.

Edinger-Westphal nucleus (part of the oculomotor nucleus)

Oculomotor nerve (CN III), to the ciliary ganglion (and from there to the ciliary muscle and pupillary sphincter)

Nucleus of the solitary tract

Dorsal motor nucleus of the vagus

Solitary tract Afferents s from thoracic, abdominal and cranial viscera vi (via cranial nerves IX and X)

Nucleus ambiguus am Vagus nerve (CN X), N X) to parasympathetic ganglia for thoracic and abdominal viscera

Afferents from taste buds (via cranial nerves VII, IX, and X)

Visceral afferents affere for sympathetic reflexes and visceral pain p (dorsal roots T1–L3) Intermediolateral cell column n (spinal segments T1–L3) 3)

Spinal ventral roots ots T1–L3, T1 to sympathetic ganglia Afferents from p pelvic viscera (dorsal roots S2–S S2–S4)

Sacral parasympathetic nucleuss (spinal segments S2–S4) 4)

Spinal ventral roots ots S2–S4, S2 to parasympathetic ganglia for pelvic viscera

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Figure 8.14  The principal circuit of the basal ganglia, shown for the putamen (left side of the figure) and caudate nucleus (right side of the figure). Excitatory connections are shown in green, inhibitory connections in red.

The basal ganglia, which include the striatum,a globus pallidus, subthalamic nucleus, and substantia nigra, are prominently involved in motor control (and in cognitive functions as well, through parallel connections with other CNS areas). They affect movement not by projecting to motor neurons in the spinal cord or brainstem, but rather by influencing the output of the cerebral cortex. The principal anatomical circuit underlying this influence is a series of parallel loops of the type indicated in the inset below: A relatively widespread area of cerebral cortex projects to a particular region of the striatum, which by way of the globus pallidus and thalamus feeds back to the cerebral cortex (typically to a frontal or limbic area). Most parts of the cerebral cortex, and the hippocampus and amygdala as well, participate in such loops. Association areas of cortex are related most prominently to the caudate nucleus, somatosensory and motor cortex to the putamen, and limbic areas to the ventral striatum. The substantia nigra and subthalamic nucleus form parts of additional basal ganglia circuitry, as indicated in Figs. 8.17 and 8.18.

Cerebral cortex Cortical neuron Thalamus

Striatum

Caudate nucleus Globus pallidus

men Puta

Cortical neuron on

Thalamus halamus

Caudate nucleus

Globus palliduss Cortical neuron

a

Striatum refers to the combination of caudate nucleus, putamen, and nucleus accumbens. (Nucleus accumbens and adjacent parts of the caudate, putamen, and basal forebrain are often referred to as the ventral striatum.)

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Figure 8.15  Major connections of the striatum; afferents on the left, efferents on the right. Excitatory connections are shown in green, inhibitory connections in red. (Inputs from the compact part of the substantia nigra are shown in a third color because they excite some striatal neurons and inhibit others.)

The most prominent afferents to the striatum arise in the cerebral cortex, substantia nigra (compact part), and intralaminar nuclei of the thalamus (especially the centromedian and parafascicular nuclei). Although not portrayed in this figure, cortical inputs are topographically organized: Association areas project mainly to the caudate nucleus, somatosensory and motor areas to the putamen, and limbic areas (including the hippocampus and amygdala) to the ventral striatum. The implication of these differing inputs, borne out by other aspects of basal ganglia connections and by behavioral studies, is that the different parts of the striatum have distinct functions. Striatal efferents form the next stage in the path back to cerebral cortex by projecting to both segments of the globus pallidus and to the reticular part of the substantia nigra, which in most respects may be considered an extension of the globus pallidus (internal segment).

Cortical neuron

CM, centromedian nucleus PF, parafascicular nucleus Cortical neuron Caudate nucleus

CM Putamen

PF

Putamen

Globus pallidus (both internal and external segments)

Caudate nucleus

Caudate nucleus

Substantia nigra (compact part)

Substantia nigra (reticular part)

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Figure 8.16  Major connections of the globus pallidus; afferents on the left, efferents on the right. Excitatory connections are shown in green, inhibitory connections in red.

The globus pallidus is prominently subdivided over most of its extent into an external segment (adjacent to the putamen) and an internal segment (adjacent to the internal capsule). Both segments (as well as the reticular part of the substantia nigra, SNr) receive inputs from the striatum. The subthalamic nucleus provides a prominent excitatory input to the internal segment through fibers that penetrate the internal capsule as a series of small bundles collectively called the subthalamic fasciculus. The external (GPe) and internal (GPi) segments of the globus pallidus have distinct efferent projections. GPe projects to the subthalamic nucleus through the subthalamic fasciculus. (GPe also has widespread inhibitory outputs to other parts of the basal ganglia, omitted from this figure to keep it from getting too complicated.) GPi and SNr, in contrast, form the next stage in the path back to cerebral cortex, by projecting to the thalamus. Some efferents from GPi penetrate the internal capsule as a series of small fiber bundles collectively called the lenticular fasciculus; others emerge from the inferior surface of GPi and hook around the internal capsule in the ansa lenticularis. The ansa lenticularis and lenticular fasciculus join cerebellar efferents underneath the thalamus to form the thalamic fasciculus. Although pallidal efferents in this figure are portrayed as ending in the ventral lateral nucleus, many actually end in the ventral anterior nucleus. Others reach more widespread thalamic sites (as might be expected in view of the striatal inputs from diverse cortical areas), such as the dorsomedial nucleus.

Caudate nucleus

VL

Putamen

TF GPe GPi STF

LF STh

STF ST

STh

Abbreviations: AL, ansa lenticularis GPe, globus pallidus (external segment) GPi, globus pallidus (internal segment) LF, lenticular fasciculus STF, subthalamic fasciculus STh, subthalamic nucleus TF, thalamic fasciculus VL, ventral lateral nucleus of the thalamus

Caudate nucleus

Putamen

GPe LF GPi AL L

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Figure 8.17  Connections of the substantia nigra. Excitatory connections are shown in green, inhibitory connections in red. (Projections from the compact part of the substantia nigra are shown in a third color because they excite some striatal neurons and inhibit others.)

The substantia nigra is almost like two separate and distinct neural structures laminated together. The reticular part (SNr), adjacent to the corticospinal and corticopontine fibers of the cerebral peduncle, is functionally a displaced part of the globus pallidus (internal segment); it receives inputs from the striatum and subthalamic nucleus and projects to the thalamus. (As in the case of the globus pallidus, its thalamic projections extend beyond the ventral anterior and ventral lateral nuclei, although this is not indicated in this figure.) The compact part (SNc) is a collection of darkly pigmented neurons (from which the substantia nigra derives its name) that receive inputs from the striatum and other sites, then project to the putamen and caudate nucleus and release dopamine there; their degeneration leads to Parkinson’s disease. A comparable set of dopaminergic neurons in the nearby ventral tegmental area projects to the ventral striatum, frontal cortex, and amygdala. VL Striatum

VA

STh

SNc

Substantia nigra

SNr

(compact part)

Abbreviations: SNc, substantia nigra (compact part) SNr, substantia nigra (reticular part) STh, subthalamic nucleus VA, ventral anterior nucleus of the thalamus VL, ventral lateral nucleus of the thalamus

Red nucleus

e

l nc

u ed lp ra eb

er

C

Substantia nigra (reticular part)

Ventral tegmental area

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Figure 8.18  Connections of the subthalamic nucleus. Excitatory connections are shown in green, inhibitory connections in red.

Despite its relatively small size, the subthalamic nucleus has surprisingly widespread connections, with inputs from the cerebral cortex (especially motor cortex) and interconnections with the thalamus and reticular formation and with several other nuclei of the basal ganglia. The most important of these connections from a functional standpoint may be inputs from the external segment of the globus pallidus and outputs to the internal segment of the globus pallidus (and to the reticular part of the substantia nigra). These form part

of an indirect route through the basal ganglia (see inset below). One general strategy used by the basal ganglia may be to facilitate some cortical activities by means of signals conveyed in the direct route (described in Fig. 8.14), while simultaneously suppressing competing cortical activities by means of signals in this indirect route. However, there is undoubtedly more to the story than this; it does not take into account, for example, the widespread inhibitory projections of GPe to sites other than the subthalamic nucleus.

Cortical neuron Cerebral cortex Cortical neuron

Thalamus Globus pallidus (internal segment)

Striatum Thalamuss

Subthalamic nucleus

Striatum S tria atum

Cortical neuron euron Globus pallidus (external segment)

Subthalamic nucleus Globus pallidus (internal segment)

Globus pallidus (external segment)

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Figure 8.19  Gross anatomy of the cerebellum; shown here is the medial surface of a hemisected cerebellum (A), and the same cerebellum before hemisection seen from superior (B), posterior (C), and anterior (D) viewpoints. (See Fig. 1.9 for additional views of the same cerebellum).

The cerebellum is even more highly convoluted than the cerebral hemispheres; this makes room for a large expanse of uniformly organized cerebellar cortex (see Fig. 8.21). Its fissures are mostly oriented transversely, and prominent ones are used as landmarks to divide the cerebellum into lobes and lobules. Thus the very deep primary fissure separates the anterior and posterior lobes,

and the posterolateral fissure separates the posterior and flocculonodular lobes. Along lines roughly at right angles to the fissures, the entire cerebellum is divided into a narrow vermis that straddles the midline and a much larger hemisphere on each side.

Vermis

Primary fissure

(anterior lobe)

Vermis

Hemisphere

(posterior lobe)

(anterior lobe)

Nodulus (part of the vermis)

Posterolateral fissure Hemisphere (posterior lobe)

Tonsil

A

(part of the posterior lobe hemisphere)

Anterior lobe: Anterior

B

vermis hemisphere

Superior

Cerebellar peduncles

Superior

D

C Posterior lobe:

Tonsil

hemisphere vermis

(part of the posterior lobe hemisphere)

Nodulus

Flocculus

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Figure 8.20  Routes into and out of the cerebellum: the cerebellar peduncles.

SUPERIOR Middle cerebellar peduncle

Inferior cerebellar peduncle

Superior cerebellar peduncle

Vermis

Nodulus Flocculus

Choroid plexus

PICA branch

Tonsil

Choroid plexus

(A) Ventral surface of a cerebellum that had been removed from the brainstem by severing the cerebellar peduncles. The view is as if one were looking dorsally from the floor of the fourth ventricle toward its roof. PICA, Posterior inferior cerebellar artery.

(C) The middle cerebellar peduncle is the input route for information from cerebral cortex. Corticopontine fibers traverse the internal capsule and cerebral peduncle and terminate in pontine nuclei. Pontocerebellar fibers then project through the contralateral middle cerebellar peduncle to nearly all areas of the cerebellar cortex.

(B) The inferior cerebellar peduncle is the major input route for fibers from the inferior olivary nucleus, vestibular nuclei, trigeminal nuclei, reticular formation, and spinal cord. (The inferior peduncle also contains some cerebellar efferents, particularly those bound for vestibular nuclei.)

(D) The superior cerebellar peduncle is the major output route from the cerebellum. Cerebellar cortex projects to a series of deep cerebellar nuclei, most of whose axons leave the cerebellum through this peduncle. (A few spinocerebellar afferents also travel through the superior peduncle.)

C B

D

(E) The planes of section shown in this figure. (The odd-looking section in D is part of Fig. 6.5A turned upside down so that its orientation more closely resembles that of B and C.)

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Figure 8.21  The structure of cerebellar cortex. (A) Cross section of a single folium (as indicated in the inset). (B) Oblique longitudinal section of a folium. (C) Longitudinal section of a folium. (D) Cross section of a single folium from a human cerebellum, stained with hematoxylin and eosin. ([A–C] Modified from Ramón y Cajal S. Histologie du système nerveux de l’homme et des vertébres, Paris, 1909–1911, Norbert Maloine. [D] Provided by Dr. Nathaniel T. McMullen, Department of Cellular and Molecular Medicine, The University of Arizona College of Medicine.)

A The lobes and lobules of the cerebellum are further subdivided by smaller sulci into a large number of folia. Each folium is covered by a remarkably uniform and precisely ordered cortex. Most of Purkinje the various cell types contained in this cortex are indicated in A, cell but the basic organization is one in which two types of afferent fibers (mossy fibers and climbing fibers) enter the cortex and one type of axon (Purkinje cell axons) leaves to convey information to the deep cerebellar nuclei. Climbing The climbing fibers all come from one place—the contralateral fiber inferior olivary nucleus—and wrap around the proximal dendrites of Purkinje cells, forming powerful excitatory synapses. All other cerebellar afferents (other than a complement of the diffuse modulatory inputs indicated in Figs. 8.38 to 8.41) enter the cerebellum as mossy fibers and terminate on the vast numbers of tiny granule cells in the granular layer. (Granule cells account for half of the neurons in the CNS.) Granule cell axons ascend toward the cerebellar surface and bifurcate in the molecular layer to form parallel fibers, which run parallel to the long axis of a given folium. In so doing, each parallel fiber intersects the flattened, transversely oriented dendritic trees of hundreds of Purkinje cells, where they make excitatory synapses. Parallel fibers

VIEW IN B

VIEW IN C Stellate cell Basket cells Golgi cell

Granule cells

Mossy fiber

VIEW IN A

B

VIEW IN C

Purkinje cells

Purkinje cell dendrites

Basket cell axon

Parallel fibers Climbing fiber Molecular layer

D

VIEW IN B

C S

ce urfa

Molecular layer Purkinje cell layer

of fo

lium

Parallel fibers Purkinje cell dendrite

VIEW IN A Purkinje cell

Granular layer White matter

Granule cells

Purkinje cells Granular layer White matter

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Figure 8.22  (A) Afferents to the cerebellum.

The cerebellum receives afferent inputs of three broad categories: afferents conveying information from the cerebral cortex, afferents conveying sensory information from a variety of subcortical sites, and climbing fibers from the contralateral inferior olivary nucleus.

Cerebral cortical input (mostly, but not entirely, from motor and somatosensory areas) reaches the cerebellum through the middle cerebellar peduncle after a relay in the pontine nuclei. Most sensory information, arising most prominently in the spinal cord and vestibular nuclei, arrives via the inferior cerebellar peduncle (although a small amount traverses the superior peduncle). Axons leaving each inferior olivary nucleus travel through the contralateral inferior cerebellar peduncle before ending in the cerebellum as climbing fibers. (The connections of the cerebellum are actually more widespread than this simple account would indicate, and it seems to have correspondingly broader functions. For example, interconnections between the cerebellum and the hypothalamus have been described, and the cerebellum plays a role in coordinating autonomic functions. Cortical inputs from association areas such as prefrontal cortex indicate that the cerebellum, like the basal ganglia, is also involved in higher cognitive functions.)

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CHAPTER 8  Functional Systems Figure 8.22 (Continued) (B) Afferents to the cerebellum, continued.

Superiorr cerebellarr peduncle e

Motor, premotor and somatosensory cortex (other areas also contribute)

Climbing fibers

Internal cap capsule

(to all areas of cerebellar cortex)

le nc du e lp bra e r Ce

Inferior cerebellar peduncle

Anterior spinocerebellar tract Cer Cerebral cortex cort

Pontine nuclei

Internal capsule, cerebral peduncle

Middle cerebellar peduncle

Middle cerebellar Middl b ll p peduncle d l Po ntine Pontine nuc clei nuclei

Transverse fibers of the basal pons (p (pontocerebellar fibers)

Vestibular nuclei Inferior cerebellar peduncle

To all areas of cerebellar cortex

Lateral cuneate nucleus L (receives large-diameter afferents from the arm)

Anterior spinocerebellar tract

Inferio olivary nucleus Inferior

Large-diameter ge-diamete er afferents afferen ts from the leg le eg

Clarke’s nucleus C ((T1–L3) T

Anterior spinocerebellar tract Posterior spinocerebellar tract

(sparsely to the flocculonodular lobe)

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Figure 8.23  (A) Efferents from the cerebellum to the forebrain.

Purkinje cell axons are the sole output from cerebellar cortex. Some leave the cerebellum entirely, through the inferior cerebellar peduncle, to reach the vestibular nuclei. Most, however, project to a series of deep cerebellar nuclei in the roof of the fourth ventricle, which in turn provide most of the output from the cerebellum. There are three deep cerebellar nuclei on each side, arranged in a lateral-to-medial sequence: the dentate, interposed,b and fastigial nuclei. This arrangement of the nuclei corresponds to three longitudinal zones of cerebellar cortex: the large, lateral part of the hemisphere; a smaller, medial part of the hemisphere (also called the intermediate zone); and the vermis most medially. The pairing of deep nuclei and longitudinal zones of cortex is a reflection of functional subdivisions within the cerebellum that are also reflected in cerebellar inputs and outputs. The lateral part of each cerebellar hemisphere receives its major inputs from the cerebral cortex (motor, somatosensory, and other, more widespread areas) via pontine nuclei. Its outputs then influence the activity of motor and premotor cortex through a pathway involving the dentate nucleus and contralateral thalamus (primarily the ventral lateral nucleus). It is thought to play a role in planning skilled movements. The medial part of each cerebellar hemisphere receives information about the limbs from two major sources—motor cortex (via pontine nuclei) and the spinal cord (via spinocerebellar tracts). It is thus strategically positioned to compare intended and actual movements and to assist with moment-to-moment correction of movement by way of connections with the interposed nucleus and motor cortex (via the thalamus). The vermis receives information about axial muscles and body position from the vestibular nuclei and spinal cord and, through the fastigial nucleus, is involved in the maintenance and adjustment of posture. Most of this is accomplished at the level of the brainstem (see Fig. 8.24), and the connections of the fastigial nucleus with the thalamus are relatively minor. Finally, the flocculonodular lobe (which does not fit comfortably into this longitudinal zonation scheme) is critically involved in eye movements by way of its connections with the vestibular nuclei.

b The interposed nucleus is itself a combination of the more lateral emboliform nucleus and more medial globose nucleus.

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CHAPTER 8  Functional Systems Figure 8.23 (Continued) (B) Efferents from the cerebellum to the forebrain, continued.

Outputs from the fastigial nucleus to motor cortex (trunk area)

Outputs from the dentate nucleus to motor and premotor cortex

Outputs from the interposed nucleus to motor cortex (limb areas) Internal capsule

Thalamus (primarily VL)

Deep cerebellar nuclei: fastigial

Decussation of the superior cerebellar peduncles Interposed nucleus Cerebellar cortex: medial hemisphere lateral hemisphere

Red nucleus

Superior cerebellar peduncle Fastigial efferents cross within the cerebellum Fastigial nucleus Cerebellar cortex (vermis)

Decussation of the superior cerebellar peduncles Superior cerebellar peduncle Cerebellar cortex (hemisphere)

Dentate nucleus

interposed

dentate

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Figure 8.24  (A) Efferents from the cerebellum to the brainstem.

Each of the deep cerebellar nuclei also has outputs to sites in the brainstem; in the case of the fastigial nucleus, these represent its major connections. As the superior cerebellar peduncle passes through or around the red nucleus, some of its fibers synapse on rubral neurons (nucleus ruber is Latin for “red nucleus”). A relatively small part of the red nucleus gives rise to the rubrospinal tract, which decussates and proceeds to the spinal cord. This is one route through which the cerebellum helps make corrections to ongoing movements, but it is relatively unimportant in humans. Most neurons of the red nucleus project instead to the ipsilateral inferior olivary nucleus via the central tegmental tract. In addition, some fibers leave the superior cerebellar peduncle as it traverses the brainstem, turn caudally, cross as the descending limb of the superior cerebellar peduncle, and reach the inferior olivary nucleus directly. The functional significance of these cerebellum–(red nucleus)–inferior olivary nucleus connections is not known with certainty, but they may play a role in motor learning. The fastigial nucleus, consistent with its role in postural adjustments, projects bilaterally to the vestibular nuclei and reticular formation. Some of its efferents leave the cerebellum uncrossed through the inferior cerebellar peduncle. Others cross the midline within the cerebellum, hook over the top of the superior cerebellar peduncle (as the uncinate fasciculus), and join the contralateral inferior cerebellar peduncle.

CHAPTER 8  Functional Systems Figure 8.24 (Continued) (B) Efferents from the cerebellum to the brainstem, continued.

Red nucleus

Superior cerebellar peduncle: decussation descending limb

Interposed nucleus

Uncinate fasciculus Uncina Fastigial Fastig nucleus

Dentate nucleus

Inferior cerebellar peduncle In

Inferior cerebellar peduncle

Vestibular nuclei RF R

Vestibular nuclei RF CTT

Vestibular nuclei Vestibular nuclei Reticular formation Inferior olivary nucleus

RF = reticular formation CTT = central tegmental tract

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Figure 8.25  (A) Projections of thalamic relay nuclei to the cerebral cortex (not shown: gustatory projections from VPM to the insula).

From F rom Fig. 7.8 7

From Fig. 7.7

From Fig. 7.6

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CHAPTER 8  Functional Systems

Mammillothalamic tract

To visual cortex (17) via SP & RP

VL

To somatosensory cortex (3, 1, 2) via PL

VA

To cingulate gyrus via PL

A

To supplementary motor area (6) via PL

To cingulate gyrus via AL

To motor and premotor cortex (4, 6) via PL

To somatosensory cortex (3, 1, 2) via PL

To auditory cortex (41) via SP

To somatosensory cortex (3, 1, 2) via PL

To visual cortex (17) via SP & RP

Figure 8.25 (Continued) (B) Projections of thalamic relay nuclei to the cerebral cortex, continued (numbers = Brodmann’s areas).

LD VA VL VPL * Medial geniculate Thalamic fasciculus

Brachium of the inferior colliculus

Trigeminal projections in medial lemniscus and spinothalamic tract

Medial lemniscus, spinothalamic tract

VPL

Abbreviations for thalamic nuclei: A, anterior LD, lateral dorsal VA, ventral anterior VL, ventral lateral VPL, ventral posterolateral *, ventral posteromedial

Optic tract

Lateral geniculate

Parts of the internal capsule: AL, anterior limb PL, posterior limb RP, retrolenticular part SP, sublenticular part

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Figure 8.26  (A) Projections of thalamic association nuclei to the cerebral cortex.

From Fig. 7.8

From Fig. 7.7

From Fig. 7.6

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CHAPTER 8  Functional Systems

Lateral posterior

Pulvinar

Lateral posterior

Abbreviations: Parts of the internal capsule: AL, anterior limb PL, posterior limb RP, retrolenticular part SP, sublenticular part Other: P-O-T, parietal/occipital/temporal association cortex

Pulvinar

To P-O-T via RP

To P-O-T via PL & SP

To somatosensory association cortex (5, 7) via PL & RP

Dorsomedial

To P-O-T via SP

To prefrontal via AL

To prefrontal via AL

To P-O-T via SP

To P-O-T via PL & SP

To somatosensory association cortex (5, 7) via PL & RP

To P-O-T via RP

Figure 8.26 (Continued) (B) Projections of thalamic association nuclei to the cerebral cortex, continued (numbers = Brodmann’s areas).

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Figure 8.27  (A) The internal capsule.

1. An axial section, demonstrating four of the five parts of the internal capsule.

2. The posterior limb and the retrolenticular and sublenticular parts of the internal capsule in coronal sections.

3. The entire internal capsule, shown in a dissection of the lateral surface of the brain. Because the temporal lobe was removed in this dissection, fibers traveling through the sublenticular part from the medial geniculate nucleus to auditory cortex are no longer present. (Modified from Ludwig E, Klingler J. Atlas cerebri humani. Boston: Little, Brown & Co.; 1956.)

The internal capsule is a compact bundle of fibers traveling to or from the cerebral cortex. Above the internal capsule, the same fibers fan out within the hemisphere as the corona radiata; below it, many of them continue on into the cerebral peduncle. The internal capsule is shaped somewhat like an incomplete cone that partly surrounds the lenticular nucleus. Relationships between parts of the cone and the lenticular nucleus are used to define five regions: the anterior limb, between the lenticular nucleus and the head of the caudate nucleus; the posterior limb, between the lenticular nucleus and the thalamus; the genu, at the junction of the anterior and posterior limbs; the retrolenticular part, behind the lenticular nucleus; and the sublenticular part, dipping under the posterior end of the lenticular nucleus.

CHAPTER 8  Functional Systems

169

Figure 8.27 (Continued) (B) The internal capsule, continued.

Corticospinal & corticopontine neurons

DM

A

Posterior limb Caudate nucleus

VA/VL

Anterior limb

VA/VL VPM VPL MG

Auditory cortex

Lenticular nucleus

Genu

Lenticular nucleus

To visual cortex

Posterior limb

Pul

Pul

Thalamus

Thalamus

LG

Sublenticular part

Retrolenticular part

Pul

Sources of thalamocortical fibers: A, anterior nucleus DM, dorsomedial nucleus LG, lateral geniculate nucleus MG, medial geniculate nucleus Pul, pulvinar VA/VL, ventral anterior and ventral lateral nuclei VPL, ventral posterolateral nucleus VPM, ventral posteromedial nucleus Thalamus

Cerebral peduncle

Posterior limb Corona radiata

Retrolenticular part

Anterior limb Sublenticular part Depression left by removing lenticular nucleus Thalamic neurons (on the other side of the internal capsule)

Cerebral peduncle

Retrolenticular part Retrole (to visual cortex)

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Figure 8.28  Afferents to the hypothalamus. Various kinds of afferents are mapped out systematically in different parts of the hypothalamus, but this is not indicated in the figure. With the exception of inputs from the retina and endings in the mammillary body (MB), the exact location of endings in this figure has no significance.

The hypothalamus is tiny, accounting for much less than 1% of the weight of the CNS, but is centrally involved in essentially all homeostatic and drive-related functions. As such, it has a multitude of connections, most of them predictable from these functions. Many hypothalamic afferents are sensory, dealing with metabolic variables and the general condition of the body. Some of these are visceral afferents, arriving from places such as the spinal cord, the nucleus of the solitary tract, the parabrachial nuclei, and the periaqueductal gray. Some are collaterals of fibers in pathways to the thalamus, most prominently the spinothalamic tract. Most of these inputs arrive through the medial forebrain bundle, which travels through the reticular formation, or through the dorsal longitudinal fasciculus, which travels through the periventricular and periaqueductal gray matter; both of these bundles also convey hypothalamic efferents. Other relevant inputs arrive via the

bloodstream (not indicated in the figure): Certain hypothalamic neurons are directly sensitive to the temperature of blood passing through the hypothalamus, to its osmolality, or to its concentration of glucose, other metabolites, or various hormones. Finally, there is a direct input from a subset of retinal ganglion cells to the suprachiasmatic nucleus of the hypothalamus. The suprachiasmatic nucleus contains the master clock for circadian rhythms, and the retinal inputs help to synchronize this clock with actual day length. The hypothalamus also receives numerous inputs from prefrontal and limbic cortex, the hippocampus, the amygdala, and other subcortical limbic nuclei. Afferents from the hippocampus arrive through the fornix and largely terminate in the ipsilateral mammillary body; those from the amygdala travel through the stria terminalis or the ventral amygdalofugal pathway.

Fornix Stria terminalis Septal nuclei Ventral entral striatum From other er cortical areas as

MB Dorsal Dors longitudinal long fasciculus fasc

Orbital cortex ortex From the retina

Amygdala Am mygdala m

Hippocampus Medial Media forebrain bundle

From the spinal cord

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CHAPTER 8  Functional Systems

Figure 8.29  Efferents from the hypothalamus. Various kinds of efferents leave systematically from different parts of the hypothalamus, but this is not indicated in the figure: With the exception of neurons in the mammillary body (MB), the exact location of neurons in this figure has no significance. Other abbreviations: A, Anterior nucleus of the thalamus; Am, amygdala; DM, dorsomedial nucleus of the thalamus (as well as some other thalamic nuclei); MTT, mammillothalamic tract.

The hypothalamus projects back to some of the same sites from which it receives inputs, often via the same bundles. For example, it projects through the medial forebrain bundle to preganglionic autonomic neurons and other autonomic centers in the brainstem and spinal cord. It also projects back to prefrontal and limbic cortex and to the hippocampus, but in these cases, a thalamic relay is involved. The hippocampal projection involves the anatomically prominent mammillothalamic tract, extending from the mammillary body to the anterior nucleus of the thalamus. There are also outputs that reach the cerebral cortex directly, but these are diffuse modulatory projections that reach widespread cortical regions (see Fig. 8.41). A final set of hypothalamic outputs contributes to homeostasis by controlling the release of hormones from the pituitary gland.

The pituitary is a two-part gland, with an anterior lobe derived from the roof of the mouth and a posterior lobe that develops as an outgrowth from the hypothalamus. Hypothalamic control is exercised through a corresponding two-part system. Neurons in the walls of the third ventricle near the infundibulum produce factors (mostly peptides) that promote or inhibit the secretion of anterior lobe hormones. These factors are released near capillaries in the median eminence (which lacks a blood–brain barrier), travel down portal veins in the infundibulum, and are rereleased in the anterior pituitary. Posterior pituitary hormones are actually produced in the hypothalamus itself. Neurons in the supraoptic and paraventricular nuclei of the anterior hypothalamus produce oxytocin or vasopressin, which travels down the axons of these neurons and is released into the circulation in the posterior pituitary.

To the cingulate gyrus (and from there to the hippocampus) To limbic and prefrontal areas

DM

A

Paraventricular Par nucleus nuc

Stria terminalis

Septal nuclei

Supraoptic nucleus

To corte x (see Fig .8

.41)

MB

MTT

Median eminence

Median eminence

Dorsal longitudinal fasciculus

Infundibulum

Am Posterior pituitary

Portal vein P

Medial forebrain bundle

Venous outflow Arterial inflow

To the spinal cord

Anterior lobe Venous outflow

Posterior lobe Arterial inflow

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Figure 8.30  An overview of the limbic system.

The limbic system is a set of intricately interconnected structures that form a functional bridge between large areas of cerebral cortex and the input/output structures of the nervous system. It forms the basis of autonomic, endocrine, and behavioral responses to homeostatic challenges and events with implications for survival and reproduction, and it helps to ensure that such events are remembered. The principal structures of the limbic system are the hippocampus and amygdala in the medial temporal lobe, a collection of nuclei in and near the hypothalamus, a ring of limbic cortex that provides a link with the rest of the cerebral cortex, and the interconnections of all these areas. They are shown here in three-dimensional reconstructions of the limbic system of the same brain shown in sagittal sections in Chapter 7. Limbic structures were outlined on serial sections by Jay B. Angevine Jr.; outlines were assembled into 3D reconstructions by Cheryl Cotman.

F

Cingulate gyrus

Isthmus of the cingulate gyrus

Amygdala Hippocampus

Parahippocampal gyrus

Stria terminalis

An F S

Se

Habenula Hip

NA

Habenulointerpeduncular tract Mammillothalamic tract

H

Midbrain reticular formation (shown here as one example of limbic output to the brainstem)

AC

Hip Am

Stria terminalis

Olfactory bulb

Se

An

Abbreviations: AC, anterior commissure Am, amygdala An, anterior nucleus of the thalamus F, fornix H, hypothalamus Hi, habenulointerpeduncular tract Hip, hippocampus M, mammillary body (of the hypothalamus) MT, mammillothalamic tract NA, nucleus accumbens S, stria medullaris (of the thalamus) Se, septal nuclei

Stria medullaris (of the thalamus)

M T

AC H

Hip F Habenula

Stria terminalis

Hi

NA

M H Am

Hip

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CHAPTER 8  Functional Systems Figure 8.31  The amygdala and its input/output pathways. (3D reconstruction provided by Cheryl Cotman.)

The amygdala and hippocampus in humans are prominent examples of structures that wind up in the temporal lobe as a consequence of the C-shaped growth of the cerebral hemispheres (see Fig. 4.1). As a result, some of the pathways associated with them trace the same C shape as other parts of the hemisphere. Most connections between the amygdala and the hypothalamus and nearby areas travel through one of two routes: (1) the stria terminalis, a small but long, curved bundle of fibers that travels in the wall of the lateral ventricle adjacent to the caudate nucleus, and (2) the ventral amygdalofugal pathway (a misleading name because it contains both afferents and efferents), a loosely organized group of fibers that pass underneath the lenticular nucleus on their way to and from the amygdala.

Stria terminalis

Amygdala

Ventral “amygdalofugal” pathway

Caudate nucleus

Stria terminalis Thalamostriate (terminal) vein Thalamus Beginning of the stria terminalis

Figure 8.32  The hippocampus and fornix. (3D reconstruction provided by Dr. John Sundsten.)

The hippocampus has a much more massive output bundle, the fornix, that travels a similar C-shaped course. The fornix is a long, curved tract that starts out as fibers (the alveus) on the ventricular surface of the hippocampus. These fibers merge into the fimbria (literally “the fringe” of the hippocampus), which parts company with the dwindling hippocampus near the splenium of the corpus callosum and emerges from the temporal lobe as the crus of the fornix. Each crus then approaches its counterpart from the other hemisphere and continues traveling anteriorly, adjacent to the midline and at the inferior edge of the septum pellucidum, as the body of the fornix. The body diverges into the columns of the fornix, which travel through the hypothalamus, mostly on their way to the mammillary bodies. (The fornix also contains cholinergic afferents from the septal nuclei to the hippocampus.) Despite the size of the fornix, most hippocampal afferents and efferents actually take a more direct course to and from temporal lobe structures. These fibers, however, are distributed along the length of the hippocampus and do not form a discrete bundle.

Crus Stria terminalis (cut tangentially) Fimbria Alveus Hippocampus

Body Body Crus Body

Anterior commissure Fimbria

Column

Columns Anterior commissure

Hippocampus

Hypothalamus

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Figure 8.33  (A) Afferents to the amygdala.

The amygdala, one of the major constituents of the limbic system, is a collection of nuclei underlying the uncus of the medial temporal/limbic lobe. It is centrally involved in assessing and remembering the emotional and drive-related significance of stimuli—deciding, for example, whether to flee from something or eat it. As such, it has widespread connections with the cerebral cortex, thalamus, hypothalamus, a variety of brainstem locations, and other sites. Afferents reach the amygdala from the cerebral cortex (through the white matter of the temporal lobe), the olfactory bulb (through

the lateral olfactory tract), and from a variety of other subcortical sites (through the stria terminalis and ventral “amygdalofugal” pathway). Cortical afferents arise in limbic areas, especially orbital and anterior cingulate cortex, and in association areas, especially sensory association areas. Subcortical afferents arise in the hypothalamus (and nearby sites, such as the septal nuclei), multiple thalamic nuclei, and numerous brainstem sites, including the periaqueductal gray, parabrachial nuclei, and nucleus of the solitary tract.

CHAPTER 8  Functional Systems Figure 8.33 (Continued) (B) Afferents to the amygdala, continued.

Association areas

Cingulate gyrus

Thalamus (multiple nuclei)

Olfactory bulb

Orbital cortex

Hypothalamus Amygdala

Ventral “amygdalofugal” pathway (some also through the stria terminalis)

Brainstem (periaqueductal gray, parabrachial nuclei, other sites)

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Figure 8.34  (A) Efferents from the amygdala.

The efferents from the amygdala for the most part reciprocate its afferents, although there are none to the olfactory bulb. Efferents reach more widespread cortical areas than those in which afferents to the amygdala arise, even extending to primary sensory areas. Projections to the hippocampus help ensure that emotionally significant events are remembered, and those to the hypothalamus,

nearby regions such as the septal nuclei, and brainstem nuclei help regulate autonomic and behavioral responses to such events. In addition, efferents from the amygdala to nucleus accumbens and other parts of the ventral striatum are presumed to play a role in initiating behavioral responses to emotionally significant stimuli.

CHAPTER 8  Functional Systems Figure 8.34 (Continued) (B) Efferents from the amygdala, continued.

Somatosensory & auditory cortex

Thalamus (dorsomedial, other nuclei)

Association areas

Cingulate gyrus

Orbital cortex

Association areas

Association areas Visual cortex

Nucleus accumbens

Hypothalamus Amygdala Hippocampus

Ventral “amygdalofugal” pathway (some also through the stria terminalis)

Brainstem (periaqueductal gray, dorsal motor nucleus of X, other sites)

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Figure 8.35  (A) Afferents to the hippocampus.

The hippocampus is a specialized area of cerebral cortex (see inset in B)—conceptually, the edge of the cortical sheet—rolled into the medial temporal lobe. It extends in the wall of the lateral ventricle from an enlarged anterior end that overlaps the amygdala underneath the uncus to a tapering posterior end near the splenium of the corpus callosum.c Formally, it consists of the dentate gyrus, the hippocampus proper (also called Ammon’s horn or cornu ammonis), and the subiculum, which merges with the cerebral cortex of the parahippocampal gyrus.

c

The hippocampus actually continues over the top of the corpus callosum as a thin, apparently rudimentary, band of tissue—the indusium griseum, which is not indicated in this atlas. Hence the hippocampus, strictly defined, extends along the entire edge of the cortical mantle.

As in the case of the amygdala, the hippocampus is connected anatomically like a bridge between the diencephalon and widespread areas of cerebral cortex, in this case as the substrate for its critical role in consolidation of new memories of facts and events. Cholinergic afferents from the septal nuclei reach the hippocampus directly by traveling “backward” through the fornix, but most other inputs are relayed by adjacent parts of the anterior parahippocampal gyrus (the entorhinal cortex). Afferents to entorhinal cortex from posterior parts of the cingulate gyrus travel through the cingulum, a curved fiber bundle underlying the gyrus; those from association areas and the amygdala travel through the white matter of the temporal lobe. To simplify this figure, all cortical afferents are shown as projecting to entorhinal cortex, and all afferents from the amygdala as projecting directly to the hippocampus itself; in fact, each does both in complex patterns.

179

CHAPTER 8  Functional Systems Figure 8.35 (Continued) (B) Afferents to the hippocampus, continued. (Inset provided by Pamela Eller, University of Colorado Health Sciences Center.)

In cross section, the hippocampus is made up of two interlocking C-shaped strips of cortex (the dentate gyrus and the hippocampus proper) and the subiculum, which is a transitional zone continuous laterally with the hippocampus proper and medially with entorhinal cortex. The hippocampus proper is itself further subdivided into four longitudinal strips called CA fields (CA for cornu ammonis). Abbreviations: C, Tail of the caudate nucleus; CA, hippocampus proper (cornu ammonis); D, dentate gyrus; F, fimbria; LGN, lateral geniculate nucleus; LV, inferior horn of the lateral ventricle; ST, stria terminalis; Sub, subiculum.

Thalamus (anterior nucleus)

Cingulum

Cingulate gyrus

Association areas

Mammillary body

Entorhinal cortex Association areas

Association areas

Septal nuclei

Fornix

Choroid plexus LGN

Hippocampus

C

ST

Amygdala

F

Alveus

CA

D

D D Sub

LV CA

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Figure 8.36  (A) Efferents from the hippocampus.

The anatomically most prominent efferent pathway from the hippocampus is the fornix (see Fig. 8.32), through which hippocampal pyramidal cells project to the septal nuclei and subicular neurons project to the septal nuclei, mammillary bodies, ventral striatum, and some cortical areas. At the level of the interventricular foramen, fornix fibers begin to splay out as they move toward their final destinations. Some pass in front of the anterior commissure (the precommissural fornix) to reach the septal nuclei and parts of the frontal lobe. Others turn posteriorly and end directly in the anterior nucleus of the thalamus. A large number descend through the hypothalamus in the column of the fornix, mostly directed toward the mammillary body. Large numbers of subicular efferents, however, bypass the fornix and project directly to entorhinal cortex and other cortical areas.

(This is presumably part of the reason why bilateral damage to the hippocampus causes a much more severe memory deficit than does bilateral damage to the fornix.) As in the case of afferents to the hippocampus, more than one hippocampal component may project in parallel to the same structure (e.g., both subiculum and entorhinal cortex to other cortical areas). The fundamental pattern of information flow in the hippocampus is unidirectional: afferents (mostly from entorhinal cortex) → granule cells of the dentate gyrus → CA3 pyramidal cells → CA1 pyramidal cells → pyramidal cells of the subiculum → output targets. Thus most of the output of the hippocampus comes from the subiculum, although some comes from hippocampal pyramidal cells.

181

CHAPTER 8  Functional Systems Figure 8.36 (Continued) (B) Efferents from the hippocampus, continued.

Association areas

Entorhinal cortex Association areas

Septal nuclei, nucleus accumbens

Mammillary body Hippocampus

Fornix

Fimbria Alveus

To and from entorhinal cortex

Dentate gyrus

CA3

Subiculum

CA1

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Figure 8.37  Neurons and pathways that use acetylcholine as a neurotransmitter.

Some neurotransmitters are found in neurons widely distributed in the nervous system. Glutamate, for example, is a common transmitter used by neurons throughout the brain at excitatory synapses. Similarly, gamma-aminobutyric acid (GABA) is a nearly ubiquitous transmitter used at inhibitory synapses. In contrast, some transmitters are found only in neurons in restricted locations (although the axons of these neurons may be distributed widely). Acetylcholine, the first neurotransmitter to be discovered, is a case in point. Acetylcholine is of major importance in the peripheral nervous system, where it is the principal transmitter released by motor neurons, preganglionic autonomic neurons, postganglionic parasympathetic neurons, and a minority of postganglionic sympathetic neurons. Within the brain, its distribution is more restricted. Acetylcholine is used as a neurotransmitter by some interneurons of the striatum and by some parts of the reticular formation. However, the most prominent collection of cholinergic neurons in the brain is found in the basal nucleus (of Meynert), the septal nuclei, and nearby parts of the basal forebrain. Collectively these neurons project through the cingulum and the external capsule (the white matter between the claustrum and the putamen) and blanket the cerebral cortex and amygdala with cholinergic endings. In addition, some of the septal neurons send cholinergic axons through the fornix to the hippocampus.

O CH3

C

O

CH3 CH2

CH2

+

N

CH3

CH3

Fornix

Cingulum

Septal nuclei

T

III RF

Basal nucleus To the amygdala To the hippocampus

X

Parasympathetic ganglion cell

III, oculomotor nucleus (representing lower motor neurons in general) X, dorsal motor nucleus of the vagus (representing preganglionic autonomic neurons in general) RF, reticular formation T, thalamus Caudate nucleus Putamen

External capsule

Basal nucleus Amygdala

CHAPTER 8  Functional Systems Figure 8.38  Neurons and pathways that use norepinephrine as a neurotransmitter.

Norepinephrine, one of the catecholamine neurotransmitters (so called because of the catechol group, shown in red, that forms part of the molecule) is the transmitter used by most postganglionic sympathetic neurons. Within the CNS, it is found in a series of pontine and medullary neurons with long, branching axons that collectively innervate most areas of the brain and spinal cord. The majority of these noradrenergic neurons (noradrenaline is a synonym for norepinephrine) are located in the locus ceruleus, a column of pigmented cells in the rostral pons (see Fig. 3.14). Others are located in the dorsal motor nucleus of the vagus, the nucleus of the solitary tract, the medullary reticular formation, and a few other sites. Ascending noradrenergic fibers (mostly from the locus ceruleus) travel through the brainstem in the dorsal longitudinal fasciculus and central tegmental tract. When they reach the cerebrum, many of them join the medial forebrain bundle, which travels longitudinally through the lateral hypothalamus. They then diverge to innervate practically all cerebral areas. Descending noradrenergic fibers (many from more caudally located neurons) similarly diverge to innervate the cerebellum, brainstem, and spinal cord. These diffuse, nearly global projections are clearly unsuitable for mediating functions that depend on precise, point-to-point communication, and instead they are involved in regulating the overall level of activity in large areas of the brain (e.g., as levels of attention and vigilance vary).

OH CH

CH2

NH2

HO OH

Medial forebrain bundle

T H LC C RF F To the amygdala To the hippocampus To the spinal cord H, hypothalamus LC, locus ceruleus RF, reticular formation T, thalamus

Locus ceruleus

Dorsal motor nucleus of the vagus

Nucleus of the solitary tract

Reticular formation

Rostral medulla

Rostral pons

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Figure 8.39  Neurons and pathways that use dopamine as a neurotransmitter.

Dopamine is a second major catecholamine neurotransmitter (so called because of the catechol group, shown in red, that forms part of the molecule). Most dopaminergic neurons are located in the midbrain, either in the substantia nigra (compact part) or in the medially adjacent ventral tegmental area. They project rostrally to most parts of the forebrain in three partially overlapping streams of fibers. The first of these streams is the projection from the substantia nigra (compact part) to the caudate nucleus and putamen (see Fig. 8.17). Because of its origin in the midbrain, this nigrostriatal pathway is also referred to as the mesostriatal dopaminergic pathway (midbrain = mesencephalon). Mesolimbic and mesocortical fibers originate mainly in the ventral tegmental area, medial to the substantia nigra, and project through the medial forebrain bundle to limbic-related subcortical structures (such as the amygdala, septal nuclei, and ventral striatum) and to cerebral cortex (especially motor and limbic areas). Additional dopaminergic neurons are found in the retina and in the hypothalamus. The latter project to the median eminence, where dopamine released into capillaries of the pituitary portal system regulates the secretion of prolactin by the anterior pituitary (see Fig. 8.29).

CH2 HO OH

P C SV S, S,V

C T

H A H C HC Medial forebrain bundle A, amygdala C, caudate nucleus H, hypothalamus HC, hippocampus P, putamen S, septal nuclei T, thalamus V, ventral striatum

Substantia nigra (compact part)

Ventral tegmental area

CH2

NH2

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CHAPTER 8  Functional Systems Figure 8.40  Neurons and pathways that use serotonin as a neurotransmitter.

Medial forebrain bundle

Serotonin (shown below), a derivative of tryptophan, is used as a neurotransmitter by a collection of neurons located at most brainstem levels in a series of raphed nuclei. Serotonergic neurons, like noradrenergic neurons, give rise to widely branched axons that innervate most parts of the CNS, including the hypothalamus, striatum, and thalamus. Serotonin, like norepinephrine, is thought to be involved in regulating the overall level of activity in the brain.

S T H

d

The Greek word rhaphe means “seam” and is used in this case to refer to the midline seam between the two halves of the brainstem.

To the amygdala Raphe nuclei

To the hippocampus HO

CH2

CH2

NH2

H, hypothalamus S, striatum T, thalamus

To the spinal cord

N H

Rostral pons

Caudal midbrain

Rostral medulla Caudal pons

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Figure 8.41  Modulatory outputs of the hypothalamus. Abbreviations: C, Caudate nucleus; H, hypothalamic histaminergic neurons; LC, locus ceruleus; P, putamen; R, raphe nuclei; S, septal nuclei; T, thalamus.

The hypothalamus projects back to cortical areas and the hippocampus by way of the thalamus, but it also contains two populations of neurons with widespread modulatory outputs directly to the cerebral cortex and to other CNS targets. These neurons play important roles in the sleep-wake cycle. Neurons of the first group (below right) are located near the mammillary bodies and use the monoamine histamine as a neurotransmitter. Much like the serotonergic neurons in Fig. 8.40, they essentially blanket the CNS with endings, including projections to brainstem components of the modulatory network. Neurons of the second group (below left) are located in the lateral hypothalamus, near the fornix, and use neuropeptides called orexins (also called hypocretins) as transmitters. Their projections to the striatum, globus pallidus, and cerebellum are limited, but otherwise are widely distributed to other parts of the CNS (including the histaminergic neurons).

N CH2 N H

CH2

NH2

Histamine Medial forebrain bundle

P

C S

C T

Medial forebrain bundle

LC L R To the amygdala To the hippocampus

S

To the spinal cord

T H

LC L R

To the amygdala To the hippocampus To the spinal ccord ord

Fornix (column)

9  Clinical Imaging* For many decades, the central nervous system (CNS) of living individuals could be examined only indirectly, for example by using x-rays to study changes in the bones surrounding the CNS or the blood vessels around or within it. In addition, these imaging studies involved projecting all the x-ray density under investigation in the head (a three-dimensional structure) onto a two-dimensional sheet of film. As a result, the images of structures actually separated in space (e.g., the middle cerebral and anterior cerebral branches in Fig. 9.17A) are superimposed on each other in these studies. The past 40 years have seen revolutionary changes in clinical imaging, partly a result of the use of computers to reconstruct two-dimensional “slices” at various levels of a patient’s head (i.e., tomography) and partly a result of the ability to construct images based on parameters other than x-ray density. The most commonly used clinical imaging techniques at present are x-ray computed tomography (CT) and magnetic resonance Gray matter: cerebral cortex caudate nucleus

imaging (MRI). CT provides images based on x-ray density, so structures that attenuate x-rays, such as bone, appear light; areas filled with air or cerebrospinal fluid, which do not attenuate x-rays as much, appear much darker. Appropriate techniques can accentuate brain, bone, or blood (Figs. 9.1 to 9.3). MRI (Fig. 9.4), in contrast, provides images based on chemical concentrations (most commonly emphasizing the concentration of free water). This chapter provides a series of examples of the use of CT and MRI to demonstrate normal anatomy in clinical imaging. In addition, although traditional angiographic techniques are no longer used very often, they still yield the most highly detailed images of the cerebral vasculature, so examples of angiograms are also provided. *With gratitude for the images and assistance provided by Raymond F. Carmody, MD, Elena M. Plante, PhD, and Joachim F. Seeger, MD, my colleagues at The University of Arizona.

Nasal bone Cerebrospinal fluid (lateral ventricle)

Ethmoidal air cells Sphenoid bone (and sinuses)

White matter (internal capsule)

Calcified choroid plexus

Bone (skull)

Middle cerebral a.

Figure 9.2  An axial (approximately horizontal) CT scan, adjusted so that the gray scale is distributed over the entire range of cranial and intracranial x-ray densities. Air is black, but little soft-tissue or fluid detail can be seen. However, the details and relative densities of different bones (e.g., sphenoid versus temporal) are apparent. (Provided by Dr. Raymond F. Carmody.)

Skull: outer table diploë inner table

Eye (vitreous)

Posterior cerebral a.

Posterior communicating a.

Mastoid air cells

(petrous part)

Cerebrospinal fluid (superior cistern)

Figure 9.1  An axial (approximately horizontal) CT scan, demonstrating the relative x-ray densities of some cranial structures. The range of x-ray densities in the head, from bone through brain to air, is much greater than the human visual system can discriminate as a series of gray shades. In this case, the computer was adjusted so that the gray scale was applied to the x-ray density of brain and cerebrospinal fluid. Hence, bone is uniformly white, and fluid is black (as air would be); gray matter is very slightly more x-ray dense than white matter, so the two can be differentiated from each other. (Provided by Dr. Raymond F. Carmody.)

Anterior cerebral a.

Temporal bone

Sigmoid sinus

Figure 9.3  Blood flowing through arteries and veins can be seen more easily if an iodinated, x-ray dense contrast agent is injected intravenously before the CT scan. (Provided by Dr. Raymond F. Carmody.)

Air (maxillary sinus)

Muscle (masseter)

CSF Gray matter (insular cortex)

Scalp White matter Transverse sinus Perilymph (in the cochlea)

Temporal bone (petrous part)

Figure 9.4  Parasagittal MRI. The concentration of water ranges from very low (air, bone) to intermediate levels (brain, muscle) to very high (cerebrospinal fluid [CSF], perilymph), allowing all of these to be differentiated. The lack of signal from certain spaces that contain a lot of water—blood vessels—is explained later. (Provided by Dr. Raymond F. Carmody.)

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Figure 9.5  (A–D) A series of seven CT images at different levels of a normal brain. (Provided by Dr. Raymond F. Carmody.)

Medial rectus

H G F E D

Lens Vitreous

Lateral rectus

Sphenoid sinus

C B

Mandible (condyle)

External acoustic meatus

Basiocciput (A) The planes of the “slices” shown in B–H.

Mastoid air cells

Cerebellum

Medulla

(tonsil)

(B) Foramen magnum.

Infundibulum

Anterior & posterior clinoid processes

Frontal lobe Temporalis

Third ventricle

Hypothalamus Temporal lobe

Uncus

Lateral ventricle (inferior horn)

Cerebral peduncle Mastoid air cells

Ambient cistern

Fourth ventricle Cerebellum:

Basal pons

hemisphere vermis

(C) Pituitary gland and fourth ventricle. (The streaks cutting across the cerebellum and pons are artifacts resulting from the presence of dense bone nearby. The density in each frontal lobe results from nearby bone in the orbital roofs.)

(D) Base of the diencephalon.

189

CHAPTER 9  Clinical Imaging Figure 9.5 (Continued) (E–H) Normal CT images.

Corpus callosum:

Longitudinal fissure

genu body

Cingulate gyrus Septum pellucidum

Lateral ventricle (anterior horn)

Lateral sulcus

Caudate nucleus

Lenticular nucleus

Putamen Internal capsule:

Globus pallidus

anterior limb genu posterior limb

Third ventricle

Thalamus

Ambient cistern

Choroid plexus

Transverse fissure

(calcified, in the atrium of the lateral ventricle)

Midbrain

Superior cistern

Superior cistern (E) Inferior thalamus.

(F) Midthalamus.

Caudate nucleus Cingulate gyrus Choroid plexus (in the body of the lateral ventricle)

Corpus callosum (splenium)

Falx cerebri Choroid plexus (in the atrium of the lateral ventricle)

(G) Just above the thalamus.

(H) Above the corpus callosum.

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Figure 9.6  (A–D) A series of seven CT images from the same patient shown in Fig. 9.5. In this case an iodinated intravenous contrast agent was administered before the CT study, making blood vessels visible. (Provided by Dr. Raymond F. Carmody.)

Lens

H

Vitreous

G F E D

Sphenoid sinus

C B

Mandible (condyle)

External acoustic meatus Mastoid air cells

Basiocciput Cerebellum

(A) The planes of the “slices” shown in B–H.

(tonsil)

Vertebral artery Medulla (B) Foramen magnum.

Cavernous sinus

Middle cerebral artery

Frontal lobe Infundibulum

Anterior cerebral artery

Middle cerebral artery

Posterior cerebral artery

Posterior communicating artery

Clinoid processes Lateral ventricle (inferior horn)

Mastoid air cells

Temporal bone

Basilar artery

Cerebellum:

Basal pons

hemisphere vermis

Fourth ventricle

Pons/midbrain

Choroid plexus (in the roof of the fourth ventricle)

(C) Cavernous sinus. The infundibulum and choroid plexus appear x-ray dense because the blood–brain barrier is lacking at these sites, allowing the contrast agent to leak out.

(D) Circle of Willis.

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CHAPTER 9  Clinical Imaging Figure 9.6 (Continued) (E–H) Contrasted CT images.

Corpus callosum

Anterior cerebral artery

Putamen

(body)

Septum pellucidum

Lateral ventricle (anterior horn)

Third ventricle

Caudate nucleus

Venous angle

Internal capsule: anterior limb genu posterior limb

Putamen

Thalamus

Internal cerebral veins

Posterior cerebral artery

Midbrain

Superior cistern

Choroid plexus (in the atrium of the lateral ventricle)

Superior cistern

Straight sinus

Confluence of the sinuses

(E) Near the bottom of the thalamus.

(F) Interventricular foramen.

Caudate nucleus Choroid plexus (in the body of the lateral ventricle)

Corpus callosum (splenium)

Great cerebral vein (of Galen)

Straight sinus Choroid plexus (in the atrium of the lateral ventricle)

(G) Just above the thalamus.

Falx cerebri Superior sagittal sinus (H) Above the corpus callosum. The falx (dura mater) is outside the blood–brain barrier, so contrast agent leaks out here.

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Figure 9.7  (A–F) The use of CT to demonstrate intracranial pathology. By convention, all axial scans (both CT and MRI) are oriented with anterior toward the top of the page and the patient’s left on the right side, as though you were looking up from the patient’s feet. (Provided by Dr. Raymond F. Carmody.)

A

B

2 1

1

3

2 R

R

L

(A) CT measures x-ray density, so structures and substances more dense than brain stand out and are light. In this 31-year-old woman, blood in a recent left intracerebral hemorrhage (1) is apparent, spreading through subarachnoid space on either side of the falx cerebri (2) and through the lateral ventricle (3).

4

(B) Structures and substances less dense than brain also stand out, but are dark. In this case, two old infarcts, one (1) in part of the right middle cerebral artery territory and another (2) in the left posterior cerebral territory, are apparent in this 67-year-old woman.

3

C

L

D

1 2

5 1 2

6 R

L

R

(C) Over a period of weeks, intracranial blood breaks down and becomes less dense than brain. The chronic left subdural hematoma in this 60-year-old man has re-bled and contains a mixture of old (1) and new (2) blood. Pressure from the hematoma bows the falx cerebri toward the right (3) and squeezes out CSF on the left, so that the subarachnoid space (4, 6) and lateral ventricle (5) apparent on the right can no longer be seen on the left.

E

L

(D) An epidural hematoma (1) in a 1-year-old boy with a head injury. Because dura mater adheres tightly to the skull, these hematomas usually have a characteristic convex shape (versus the long crescent shape of subdural hematomas such as the one in C). Contused and swollen tissue (2) can also be seen at the site of injury.

F

1

2

R

L

(E) The same patient as in (D) but with the CT contrast window set to show bone detail. Now the basal and occipital skull fractures (1, 2) are visible, but the hematoma is not.

(F) The same patient as in D. Multiple bone-window images such as that in E were combined to make a three-dimensional reconstruction of the skull, showing the occipital fracture in detail.

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CHAPTER 9  Clinical Imaging Scalp Skull: outer table diploë inner table

CSF Gray matter (cerebral cortex)

White matter Flowing blood (superior sagittal sinus)

Figure 9.8  In T1-weighted images (left), white matter is lighter than gray matter and cerebrospinal fluid (CSF) is dark. Conversely, in T2-weighted images (right), white matter is darker than gray matter, and CSF is bright and prominent. In both, air and dense bone, which contain relatively few hydrogen nuclei, are dark. The appearance of flowing blood depends on a number of technical parameters, but in many instances (e.g., the T2-weighted image on the right), perturbed nuclei have left the area before the imaging measurement is made, so the blood vessel appears dark, as though no hydrogen nuclei were present. (Provided by Dr. Raymond F. Carmody.)

A B

R

L

C

Figure 9.9  Use of diffusion-weighted imaging for early detection of stroke damage. (A) On the day of a stroke, CT images fail to reveal significant damage. (B) On the same day, diffusion-weighted MRI shows areas of edema and restricted diffusion in part of the right middle cerebral artery distribution. (C) Three days later, damage in the edematous areas shows up in CT images. (Provided by Dr. Raymond F. Carmody.) Figure 9.10  Use of diffusion tensor imaging in planning a neurosurgical procedure. (A) A 20-year-old man was found to have a tumor (glioblastoma multiforme) in his left temporal lobe (1). Because part of the optic radiation travels in this part of the temporal lobe (see Fig. 8.9), diffusion tensor imaging was used before surgery to study the relationship between the tumor and the optic radiation. (B) In this axial slice through the body of the corpus callosum, fibers traveling in different directions can be distinguished. By convention, areas where it is easier for water to diffuse in an anterior-posterior direction are green, here including fibers traveling to or from the frontal (1) or occipital (3) lobes and fibers in long association bundles (2). Areas with fibers traveling in an inferior-superior 1 direction are blue, here including those in the corona radiata (4). Areas with fibers traveling in a side-to-side direction are 2 red, here including those in the corpus callosum (5). (C) At the level of the anterior commissure (1), the right optic radiation (2) has a normal course back toward the occipital lobe. The left optic radiation (3) 1 3 is bowed laterally by the tumor (4) but is outside it. (Provided by Dr. Raymond F. A Carmody.)

CT reconstructs images based on spatial variations in x-ray density, so the relatively small density differences between gray and white matter limit its ability to differentiate between different areas of the brain. In addition, the much greater x-ray density of bone can overwhelm these small gray-white differences and cause artifacts in bony areas such as the posterior fossa (see Fig. 9.5C). MRI overcomes these problems by being exquisitely sensitive to spatial variations in the concentration and physicochemical situation of particular atomic nuclei (almost always hydrogen nuclei). Nuclei with an odd number of protons or neutrons, such as hydrogen nuclei, behave like tiny magnets. Imposing a powerful magnetic field on something containing these nuclei (e.g., someone’s head) causes a net tendency for the nuclei to align themselves with the external field. Once so aligned, the nuclei preferentially absorb and then emit electromagnetic energy at a particular frequency (the resonant frequency for that kind of nucleus in that situation). Hence, applying radiofrequency pulses to a subject in a strong, static magnetic field and then measuring the spatial distributions of various time constants with which the absorbed energy is re-emitted can provide the data for construction of images based on different tissue properties. Two time constants—T1 and T2—are particularly important in clinical imaging. T1 is the time constant with which nuclei return to alignment with the static field. T2 is the time constant with which nuclei, all perturbed at the same time by radiofrequency pulses, lose alignment with each other. T1- and T2-weighted images emphasize different tissue parameters in different ways (Fig. 9.8). T1-weighted images show anatomical detail more clearly and so are used in Figs. 9.11 through 9.13. T2-weighted images, on the other hand, are highly sensitive to small changes in water concentration and so are very useful for demonstrating pathology within the brain (see Fig. 9.14A and B). MRI parameters can be adjusted in additional ways to emphasize other tissue properties. For example, diffusion-weighted images map the ease with which water can diffuse through different parts of the brain. Cells swell when their energy supply is interrupted, moving water from extracellular to intracellular spaces and making it less able to diffuse. As a result, diffusion-weighted images provide a very early indication of the areas damaged in a stroke (Fig. 9.9). Measurements can also be made of the ease with which water can diffuse in particular directions. Because it is easier for water molecules to diffuse in a direction parallel to axons than to snake their way between axons in a direction perpendicular to a tract, it is possible to use this technique to map out the locations of known pathways. Such diffusion tensor images are now commonly used in planning neurosurgical procedures (Fig. 9.10).

1

4

B

5

2

4

C

3

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Figure 9.11  (A–O) T1-weighted coronal magnetic resonance (MR) images of the brain of a young man. The same brain is shown in different planes in Figs. 9.11 through 9.13, with the planes of “section” indicated in three-dimensional reconstructions. *The brain was remapped into Talairach space (i.e., morphed to match a standard brain), which is commonly done in preparation for functional imaging studies, making the data obtained from different subjects comparable. (Provided by Dr. Elena M. Plante.)

DA

A D A D

Superior sagittal sinus

A

Optic nerve & extraocular muscles

B Superior, middle, inferior frontal gyri

Cingulate gyrus Corpus callosum (genu)

Lateral ventricle (anterior horn)

Lateral sulcus Orbital gyri Gyrus rectus

Optic nerve

Superior sagittal sinus

C

D

Cingulate gyrus

Superior, middle, inferior frontal gyri

Temporal lobe

Internal capsule (anterior limb)

Corpus callosum (body)

Caudate nucleus

Putamen

(head)

Lateral ventricle (anterior horn)

Lateral sulcus Insula

Superior, middle, inferior temp. gyri

Nucleus accumbens Optic nerve Internal carotid a.

Corpus callosum (rostrum)

Pituitary gland Parahippocampal gyrus

Occipitotemporal gyrus

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CHAPTER 9  Clinical Imaging Figure 9.11 (Continued) T1-weighted coronal MR images.

H E

E H E H

Superior sagittal sinus Falx cerebri

Cingulate gyrus

E

F

Corpus callosum (body)

Superior, middle, inferior frontal gyri

Septum pellucidum

Dura mater

Lateral ventricle

Putamen

(anterior horn)

Caudate nucleus

Putamen

Internal capsule:

Globus pallidus

anterior limb genu

Third ventricle

Insula

Superior, middle, inferior temp. gyri

Optic chiasm Optic tract Internal carotid a. Pituitary gland

Middle cerebral a.

Nucleus accumbens

Amygdala Anterior commissure

Occipitotemporal gyrus Parahippocampal gyrus

Superior sagittal sinus

G

H

Cingulate gyrus Corpus callosum (body) Lateral ventricle (body)

Hypothalamus Anterior commissure

Caudate nucleus Fornix Pr

Insula Superior, middle, inferior temp. gyri

Internal capsule: genu posterior limb

Pr

Superior, middle, inferior frontal gyri Putamen Globus pallidus

Third ventricle Optic tract Thalamus

Amygdala Lateral ventricle (inferior horn)

Mammillary body

Hippocampus Internal jugular v. Occipitotemporal gyrus Parahippocampal gyrus

Basilar a. Pr = precentral gyrus

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Figure 9.11 (Continued) T1-weighted coronal MR images.

L I

I L I L

Superior sagittal sinus Cingulate gyrus

I

Superior, middle frontal gyri

J

Corpus callosum (body) Lateral ventricle (body) Caudate nucleus Fornix

Pr

Insula

Pr

Putamen

Thalamus Internal capsule

Globus pallidus

(posterior limb)

Third ventricle Internal capsule (sublenticular part)

Optic tract

Hippocampus

Red nucleus

Cerebral peduncle Basal pons Substantia nigra

Interpeduncular cistern Superior frontal gyrus

Superior frontal gyrus

K

Central sulcus

Pr

L

Cingulate gyrus Central sulcus

Central sulcus Posterior commissure

Pr

Caudate nucleus Po

Superior, middle, inferior temporal gyri

Superior sagittal sinus

TT

Fornix

Po

Thalamus

Lateral geniculate nucleus

Aqueduct Third ventricle Internal capsule (sublenticular part)

Hippocampus Cerebral peduncle Basal pons

Middle cerebellar peduncle

Medulla

Olive Occipitotemporal gyrus Spinal cord Parahippocampal gyrus Po, Pr = postcentral, precentral gyri

TT = transverse temporal (Heschl’s) gyrus

197

CHAPTER 9  Clinical Imaging Figure 9.11 (Continued) T1-weighted coronal MR images.

OM

MO MO Superior frontal gyrus

Superior sagittal sinus

M

Superior frontal gyrus

Central sulcus

Central sulcus

Pr

Corpus callosum:

Pr

Central sulcus Inferior colliculus

N

Cingulate gyrus

Po

body splenium Po

Superior cistern

SM

Caudate nucleus

Superior, middle, inferior temporal gyri

Fornix (crus)

Thalamus Hippocampus Aqueduct Fourth ventricle Sigmoid sinus

Middle cerebellar peduncle

Cerebellum: hemisphere tonsil vermis

Medulla Spinal cord

Parahippocampal gyrus

Central sulcus Pr Po SM

Occipitotemporal gyrus

Cisterna magna

O

Pr

Corpus callosum (splenium) Po

Lateral ventricle (atrium) SM

Glomus Fornix (crus) Hippocampus

Superior, middle, inferior temporal gyri

Superior cistern Transverse sinus Fourth ventricle

Occipitotemporal gyrus Cingulate gyrus (isthmus) Cisterna magna

Cerebellum: hemisphere vermis tonsil

Po, Pr = postcentral, precentral gyri; SM = supramarginal gyrus

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Figure 9.12  (A–O) T1-weighted axial (horizontal) MR images of the brain of a young man. The same brain is shown in different planes in Figs. 9.11 through 9.13, with the planes of “section” indicated in three-dimensional reconstructions. (Provided by Dr. Elena M. Plante.)

A

D

D

A

A

Nasal septum

B

Internal carotid a. Internal jugular v.

Parotid gland

Sigmoid sinus

Vertebral a. Medulla Cerebellum:

Fourth ventricle

hemisphere tonsil

Foramen magnum

C

Cisterna magna

D

Internal carotid a.

Orbital fat

Temporal lobe Basilar a.

Pyramid Basal pons Sigmoid sinus

Fourth ventricle Cerebellum:

Inferior cerebellar peduncle Fourth ventricle

flocculus hemisphere vermis

Middle cerebellar peduncle Transverse sinus

199

CHAPTER 9  Clinical Imaging Figure 9.12 (Continued) T1-weighted axial (horizontal) MR images.

H E

Lens

H E

Orbital gyri

E

F

Gyrus rectus Amygdala

Vitreous Internal carotid a.

Lateral ventricle

Optic chiasm

(inferior horn)

Middle cerebral a.

Inferior temporal gyrus

Pituitary gland Pontine cistern Interpeduncular cistern Cerebral peduncle Aqueduct

Middle temporal gyrus

Basal pons Fourth ventricle Cerebellum: Collateral sulcus Parahippocampal gyrus

Straight sinus

hemisphere vermis

Superior sagittal sinus

Confluence of the sinuses Orbital gyri

G Optic tract

Inferior frontal gyrus (orbital part)

H Nucleus accumbens Putamen

Insula

Anterior commissure

Third ventricle Superior, middle temporal gyri

Cerebral peduncle Aqueduct Hippocampus

Superior, middle temporal gyri

Lateral ventricle: Medial geniculate nucleus Superior colliculus

inferior horn atrium

Fimbria

Superior cistern Great vein Internal cerebral vein Superior sagittal sinus

Posterior commissure

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Figure 9.12 (Continued) T1-weighted axial (horizontal) MR images.

L I

L I

Lateral ventricle

Anterior commissure Superior, inferior frontal gyri

Corpus callosum (genu)

(anterior horn)

I

J

Caudate nucleus Putamen Insula

Cingulate gyrus

Cingulate gyrus

Fornix: a g

column body

Globus pallidus Thalamus

p

a g p

Third ventricle

r

Superior, inferior frontal gyri

r

Stria medullaris (of the thalamus)

Superior temporal gyrus

Superior temporal gyrus

Fornix (crus) Lateral ventricle (atrium)

Cingulate gyrus (isthmus)

Cingulate gyrus

Corpus callosum (splenium)

Superior sagittal sinus

Visual cortex

Cingulate gyrus Superior, middle, inferior frontal gyri

K

L

Corpus callosum

Superior, middle, inferior frontal gyri

(genu)

Lateral ventricle (anterior horn)

Caudate nucleus Fornix (body)

a g

Superior temporal gyrus

p

Superior temporal gyrus

Insula Thalamus Fornix (body) Lateral ventricle (atrium/body)

Corpus callosum

Postcentral gyrus

(splenium)

Cingulate gyrus Parietooccipital sulcus Superior sagittal sinus a, g, p, r = anterior limb, genu, posterior limb, retrolenticular part of the internal capsule

Supramarginal gyrus Angular gyrus

CHAPTER 9  Clinical Imaging

201

Figure 9.12 (Continued) T1-weighted axial (horizontal) MR images.

O M

M

O M

N

Superior frontal gyrus

Caudate nucleus

Lateral ventricle

Middle frontal gyrus

(body)

Cingulate gyrus Inferior frontal gyrus Precentral gyrus Central sulcus Postcentral gyrus Supramarginal gyrus Angular gyrus Corpus callosum

Cingulate gyrus

Lateral ventricle

(body)

(body)

Superior sagittal sinus

Corpus callosum (body)

Superior frontal gyrus

O

Superior sagittal sinus

Middle frontal gyrus Inferior frontal gyrus Precentral gyrus Central sulcus

Cingulate gyrus

Postcentral gyrus Supramarginal gyrus

Superior sagittal sinus

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Figure 9.13  (A–G) T1-weighted sagittal and parasagittal MR images of the brain of a young man. The same brain is shown in different planes in Figs. 9.11 through 9.13, with the planes of “section” indicated in three-dimensional reconstructions. (Provided by Dr. Elena M. Plante.)

A

D

A Inferior frontal gyrus

A

D

D

Precentral & postcentral gyri

Middle frontal gyrus

A

D

Precentral & postcentral gyri

B

Supramarginal, angular gyri

Supramarginal gyrus Angular gyrus

Lateral sulcus

A

Transverse temporal (Heschl’s) gyrus Insula Vitreous

Orbital gyri

Transverse sinus

Transverse sinus

Cerebellum (hemisphere)

Cerebellum (hemisphere)

Sigmoid sinus Parotid gland

Inferior temporal gyrus

Sigmoid sinus

Occipitotemporal gyrus

C Middle frontal gyrus

Precentral & postcentral gyri

Precentral & postcentral gyri

Superior parietal lobule

Middle frontal gyrus Superior parietal lobule

Orbital gyri

D

Glomus

Putamen

Fimbria

Orbital gyri Lens

Hippocampus Amygdala Transverse sinus

Optic nerve

Cerebellum (hemisphere)

Cerebellum (hemisphere)

Sigmoid sinus Internal carotid a.

Hippocampus

Internal jugular v. Parahippocampal gyrus

Parahippocampal gyrus Internal carotid a.

203

CHAPTER 9  Clinical Imaging Figure 9.13 (Continued) T1-weighted sagittal and parasagittal MR images.

E G

E G

E

G E

Precentral & postcentral gyri

Precentral & postcentral gyri

Superior frontal gyrus

Superior frontal gyrus

Superior parietal lobule

Caudate nucleus

G E F

Superior parietal lobule

Caudate nucleus

Fornix

Thalamus

(crus)

b

Parietooccipital sulcus

g

Fornix (crus) Nucleus accumbens

s

Thalamus Trans. sinus Calcarine sulcus

Optic nerve & tract Cerebellum (hemisphere)

Cerebellum:

Pons

hemisphere tonsil

Tongue Internal capsule

Putamen Globus pallidus Amygdala Internal carotid a.

(posterior limb)

Medulla

Vertebral a. Fornix (body)

G

Fourth ventricle

Top of the central sulcus Cingulate sulcus (marginal branch)

Cingulate gyrus

Superior sagittal sinus

Superior frontal gyrus

Thalamus

Interventricular foramen Anterior commissure Hypothalamus Optic chiasm Pituitary gland Mammillary body Midbrain Basal pons Medulla Tongue

Posterior commissure

b g

s

Superior & inferior colliculi Straight sinus Confluence of the sinuses Fourth ventricle Cerebellum: vermis tonsil

Cisterna magna Spinal cord g, b, s = genu, body, and splenium of the corpus callosum

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Figure 9.14  (A–F) The use of MRI to show intracranial pathology. (Provided by Dr. Raymond F. Carmody.)

B

A

1

1

R

R

L

(A) This T1-weighted image shows a slight change in signal in the cerebral white matter (1) of a patient with multiple sclerosis (MS).

L

(B) In a T2-weighted image of the same patient as in (A), the MS plaque in the white matter (1) is much more apparent.

C

D

2

3 1 1

2 R

L

R

(C) The same patient as in (A) and (B). A contrast agent (gadolinium) effective in MRI studies was injected intravenously before this MRI, revealing a rim around the edge of the plaque (1) where the blood–brain barrier had broken down. Blood vessels, including the superior sagittal sinus (2), can also be seen, as can the falx cerebri (3) (because the dura mater is outside the blood–brain barrier).

E

L

(D) This T2-weighted image demonstrates the results of a stroke in the territory of the left middle cerebral artery. The damaged cerebral cortex (1) is edematous, and the increased water concentration makes it appear lighter than the neighboring cortex.

F

5 6 4 3 1

2 3

2 1

R

L

(E) A T2-weighted image showing a tumor (1) of the eighth nerve (a vestibular schwannoma, often referred to as an acoustic neuroma). Because fluids are bright in T2-weighted images, the cochlea (2) and semicircular canals (3) can also be seen.

R

L

(F) A T1-weighted image of a patient with a tumor (1 and 2, a glioblastoma multiforme) in the left temporal lobe. The tumor has a disrupted blood–brain barrier around its edges that allows contrast material to leak into it (1), and a necrotic core (2). Adjacent areas (3) appear darker than normal because of edema. The tumor has compressed the left lateral ventricle (4) and shifted parts of the left hemisphere to the right. Structures normally made visible by contrast agents include the superior sagittal sinus (5) and the falx cerebri (6).

CHAPTER 9  Clinical Imaging Blood vessels can be visualized with most imaging techniques by finding a way to make the blood contained within them differ in some way from surrounding structures. Traditional cerebral angiography uses the intravenous injection of iodinated dyes to make blood much more opaque than brain to x-rays (Fig. 9.15). More recently, MRI techniques that depend on the intrinsic properties of flowing blood have been developed (Fig. 9.16). MR angiography (MRA) has the advantage of being completely noninvasive—no intravenous contrast material is required—but the resulting images are not as detailed as those produced by traditional angiography.

A

205

An x-ray–based cerebral angiogram is typically produced by introducing a catheter into the femoral artery, threading it (under fluoroscopic control) up the aorta and into the aortic arch, then steering the catheter tip into the artery of interest. In this way, the contrast material can be introduced into a single vertebral or internal carotid artery. Once the dye has been introduced, a rapid series of radiographs can follow it as it flows through the artery, into capillaries, and then into veins (Fig. 9.15). Finally, photographic (as in Fig. 9.15) or digital (Fig. 9.21) techniques can be used to remove bone images and reveal blood vessels in relative isolation.

B

C

Figure 9.15  Movement of contrast material through the intracranial vasculature, as seen in a series of anterior-posterior (AP) views (as though you were looking at the patient’s forehead) after injection of the right internal carotid artery. (A) About 2 seconds after injection, the arteries are filled. (B) About 5 seconds after injection, the contrast agent has moved out of arteries and into capillary beds. (C) About 7 seconds after injection, the contrast agent has moved into veins and venous sinuses. (Provided by Dr. Joachim F. Seeger.)

8

9

6

1

13

2

9

3

10

1

2

A

7

5

12

4

11 8

Figure 9.16  Magnetic resonance angiography uses some of the intrinsic properties of flowing blood to create images of parts of the vasculature; appropriate adjustments of technical parameters can emphasize arteries or veins. The views in these images are as though you were looking from the front (A) or looking up from below (B) at the entire arterial supply of the brain. The internal carotid artery can be seen ascending through the neck (11), traversing the temporal bone (3), and passing through the cavernous sinus (2). The other arteries of the circle of Willis can also be seen—the anterior cerebral (1), posterior cerebral (4), and anterior (13) and posterior (7) communicating arteries—in addition to the middle cerebral artery (9), its branches on the surface of the insula (8), the vertebral (12) and basilar (5) arteries, the superior sagittal sinus (6), and even the ophthalmic artery (10). (Provided by Dr. Raymond F. Carmody.)

3

4 7

5 6

B

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Figure 9.17  The arterial phase of a right internal carotid angiogram. (A) A lateral view; the patient’s face is to the right. (B) An anterior-posterior projection; the view is as though you were looking at the patient’s forehead.

A

View in B

B

View in A

CHAPTER 9  Clinical Imaging

207

Figure 9.17 (Continued) (C) The internal carotid artery bifurcates into the anterior and middle cerebral arteries. The anterior cerebral artery in turn gives rise to two prominent branches, the pericallosal (dark blue arrows) and callosomarginal (green arrows) arteries, which curve around above the corpus callosum and supply most of the medial surface of the cerebral hemisphere. Branches of the middle cerebral artery traverse the insula (light blue arrows), emerge from the lateral sulcus ( ), and supply the lateral surface of the hemisphere. (D) In an anterior-posterior projection, the separation between anterior and middle cerebral territories can be seen more easily. (Provided by Dr. Joachim F. Seeger.)

C

Middle cerebral branches

Anterior choroidal artery

Internal carotid artery: in the cavernous sinus traversing the temporal bone ascending through the neck

Anterior cerebral artery

Eye (choroid)

Ophthalmic artery

D Anterior cerebral branches (both arteries can be seen, supplying the medial surfaces of both cerebral hemispheres)

Middle cerebral branches Middle cerebral branches: supplying the lateral surface of the cerebral hemisphere emerging from the lateral sulcus on the surface of the insula

Lenticulostriate arteries Ophthalmic artery

(a small amount of contrast medium reaches branches in the left hemisphere, via the anterior communicating artery)

Anterior cerebral artery

Anterior communicating artery

Internal carotid artery: in the cavernous sinus traversing the temporal bone ascending through the neck

Anterior choroidal artery

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Figure 9.18  The venous phase of a right internal carotid angiogram. (A) A lateral view; the patient’s face is to the right. (B) An anterior-posterior projection; the view is as though you were looking at the patient’s forehead. Flow into the transverse sinuses is typically asymmetrical; in this patient, most blood from the superior sagittal sinus flows into the left transverse sinus (more commonly it flows to the right).

A

View in B

B

View in A

209

CHAPTER 9  Clinical Imaging

Figure 9.18 (Continued) (C) Blood flows through a system of deep veins (dark blue arrows) to the straight and transverse sinuses and through a system of superficial veins (light blue arrows) mostly into the superior sagittal sinus; both systems meet at the confluence of the sinuses. (D) In an anterior-posterior view, the superior sagittal sinus occupies much of the midline, obscuring other vessels. (Provided by Dr. Joachim F. Seeger.)

C

Superior anastomotic vein

Internal cerebral vein

(of Trolard)

Superior sagittal sinus

Superior sagittal sinus

Straight sinus Terminal (thalamostriate) vein

Inferior anastomotic vein (of Labbé) Confluence of the sinuses

Venous angle

Transverse sinus

(location of the interventricular foramen)

Great cerebral vein (of Galen) Septal vein

Sigmoid sinus Sphenopetrosal vein (continuation of the superficial middle cerebral vein into the transverse sinus)

Superficial middle cerebral vein (unusually prominent in this patient)

Basal vein (of Rosenthal) Internal jugular vein

Superior anastomotic vein (of Trolard)

D

Superior sagittal sinus

Confluence of the sinuses

Basal vein (of Rosenthal)

*

Transverse sinus

Superficial middle cerebral vein Sigmoid sinus

Tip of the catheter

*A filling defect, where blood from the uninjected hemisphere enters the transverse sinus (perhaps through the left vein of Labbé).

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Figure 9.19  The arterial phase of a left vertebral-basilar angiogram. (A) A lateral view; the patient’s face is to the right. (B) An anterior-posterior projection; the view is as though you were looking at the patient’s forehead. The basilar artery appears shorter than it really is because of the angle of view—you are looking almost longitudinally along it. (The right vertebral artery is visible because the pressure of the injection propelled some contrast material into it.)

A

View in B

B

View in A

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CHAPTER 9  Clinical Imaging

Figure 9.19 (Continued) (C) The vertebral and basilar arteries and their branches supply areas below the tentorium cerebelli (location of the tentorium indicated by *), and the posterior cerebral arteries supply parts of the midbrain and supratentorial structures (including much of the thalamus). (D) The two vertebral arteries (green arrows) join to form a single, midline basilar artery (light blue arrow), which gives rise to a series of branches as it courses along the anterior surface of the pons, finally bifurcating at the level of the midbrain to form the two posterior cerebral arteries (orange arrows). (Provided by Dr. Joachim F. Seeger.)

C Posterior cerebral branch

Posterior cerebral branches

(to choroid plexus in the roof of the third ventricle)

(to medial occipital and parietal cortex)

Location of the thalamus Posterior cerebral branches (to visual cortex)

Superior cerebellar branches (outlining the superior surface of the cerebellum!)

Posterior cerebral artery

* * *

*

Superior cerebellar artery

*

Basilar artery Posterior cerebral branches

Location of the vermis

(to the temporal lobe)

Anterior inferior cerebellar artery (AICA)

PICA branches (outlining the inferior surface of the vermis)

(mostly concealed by the shadow of the temporal bone)

Posterior inferior cerebellar artery (PICA)

Vertebral artery

D

Location of the midbrain

Posterior cerebral artery

Superior cerebellar artery

Anterior inferior cerebellar artery (AICA)

ˆ

Posterior inferior cerebellar artery (PICA)

Basilar artery Vertebral artery

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Figure 9.20  The venous phase of a vertebral angiogram. (A) A lateral view; the patient’s face is to the right. (B) An anterior-posterior projection; the view is as though you were looking at the patient’s forehead.

A View in B

B

View in A

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CHAPTER 9  Clinical Imaging

Figure 9.20 (Continued) (C) A network of veins drains from the cerebellum and brainstem into the great vein or straight sinus (dark blue arrows), or into the transverse or petrosal sinuses. The medial surface of the occipital lobe drains into the superior sagittal sinus (light blue arrows). (D) In an anterior-posterior view, the straight sinus is seen almost end-on. (Provided by Dr. Joachim F. Seeger.)

Great cerebral vein (of Galen)

C

Superior sagittal sinus

Straight sinus Location of the thalamus

Confluence of the sinuses Transverse sinus

Precentral cerebellar vein (crossing the superior cistern between cerebellum and midbrain)

Superior vermian vein (outlines the top of the cerebellum)

Sigmoid sinus Internal jugular vein

D Superior sagittal sinus

Straight sinus and confluence of the sinuses

Transverse sinus

Sigmoid sinus

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Figure 9.21  (A–F) The use of angiography to show intracranial pathology. (Provided by Dr. Raymond F. Carmody.)

A

B

1 2

4

2 1

3 R

L

(A) An anterior-posterior view of a patient who had subarachnoid bleeding from a ruptured aneurysm (a balloon-like swelling of the wall of an artery). The internal carotid artery (1) was injected, and the left (2) and right (3) middle cerebral arteries and the anterior cerebral arteries (4) can be seen.

(B) The same patient as in A. Rotating the point of view by about 45 degrees makes the aneurysm (1) apparent, at a branch point of the anterior cerebral artery (2).

C

D

2 2

1

1

R (C) A 38-year-old woman with an aneurysm. A three-dimensional reconstruction based on contrast-enhanced CT scans shows the aneurysm (1), at a branch point of the middle cerebral artery (2).

E

L

(D) An angiogram of a 78-year-old man who complained of a headache reveals that the left middle (1) and anterior (2) cerebral arteries were bowed outward, as though something were distorting them.

F 1

1

(E) The same patient as in D. A lateral view shows a forward bowing of the middle meningeal artery (1).

(F) The same patient as in D. A T1-weighted MRI reveals a large meningioma (1).

10  An Introduction to Neuropathology The different diagnoses of diseases and disorders within the nervous system are made using neuropathology in coordination with clinical signs/symptoms and imaging. The imaging techniques discussed in Chapter 9, coalesced with biopsies, the use of selective antibodies to identify cellular markers, and particular stains to highlight cellular structures, are all used to make a diagnosis. This chapter will present some common neuropathological diseases/disorders. Stains used to help identify the different cells of the central nervous system (CNS) include hematoxylin and eosin (H&E), Nissl stain, Luxol-fast blue stain, and silver stains. H&E stains are the most commonly used, with the cytoplasm of cells being more acidic (eosinophilic) and staining red, whereas the nuclei and nucleoli are more basic (hematoxylinophilic) and are stained blue. Nissl bodies, which are the rough endoplasmic reticulum of neurons, are basophilic, and the use of a Nissl stain (cresyl violet) results in a dark purple highlight of the rough endoplasmic reticulum. Axons and dendrites cannot be distinguished unless there are swelling-related changes. Astrocytes lack an eosinophilic cytoplasm and have nuclei that appear large and quite clear. When astrocytes react to tissue damage, they appear eosinophilic because their cytoplasm becomes more abundant as a result of an increase in fibrous components, which also accumulate in the nerve processes. Oligodendroglia are smaller than astrocytes, with basophilic densely staining nuclei and a barely visible cytoplasm. The nuclei of microglia present with basophilic club-shaped terminations and are thus easily distinguished. Luxol-fast blue stains the myelin sheath (lipids) blue and is often used to help diagnose demyelinating diseases. Silver stains (i.e., Bodian staining) use silver, copper, and gold to stain neuronal cell bodies and nerve processes dark brown. Parts of the cells that take up the “silver” stain (called argentaffin parts) can include areas of localized axonal swelling, dendritic lesions, and Alzheimer neurofibrillary degeneration (neurofibrillary tangles [NFTs]). Other silver staining procedures enable clear visualization of amyloid components of senile plaques; immunostained images of β-amyloid proteins show similar results.

PRIMARY BRAIN TUMORS Tumors of the brain include astrocytomas, oligodendrogliomas, and ependymomas, medulloblastomas as well as several others. Originally these primary brain tumors were thought to originate from glial cells, hence the name (gliomas); recent evidence suggest that they may not only come from glial cells but also from neural stem cells and are characterized based on the expression of particular cell markers. Primary brain tumors are classified not only using stains, selective antibodies, and/or their location (i.e., intra-axial

= within the brain parenchyma, or extra-axial = outside of the brain parenchyma) but also based on how well defined the borders of the tumor are (i.e., well circumscribed vs. diffuse). In addition, there are tests, such as KI67 staining for identifying mitotic activity, performed in order to detect how rapidly the cancer is dividing, and the majority of tumors are given a “grade” (grades I-IV from slow to fast) for growth aggressiveness.

ASTROCYTOMAS Astrocytomas are thought to develop from astrocytes and may arise anywhere in the brain or spinal cord (intra-axial), yet they most often occur in the cerebrum. Astrocytomas are the most common primary CNS tumors and can be further divided based on their ability to either remain localized or diffusely infiltrate.

*

A Figure 10.1  (A) Pilocytic astrocytoma MRI-T1, parasagittal view and (B) MRI-T1 gadolinium enhanced axial view (arrows). The more localized, slow growing astrocytomas (i.e., grade I) are called pilocytic astrocytomas. These typically well-circumscribed tumors are found more often in children and young adults in areas like the cerebellum, but they are not limited to the cerebellum. These tumors are highly vascular and enhance well with contrast injection. They are often cystic (*) with a protruding solid nodule. Illustration continued on following page

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Vermis

Cerebellar hemisphere

4th Ventricle

*

Pilocytic astrocytoma

C Pons

B

D E Figure 10.1 (Continued) (C) Pilocytic astrocytoma of the pons. Though more common in the cerebellum and hypothalamus, pilocytic astrocytoma may occur anywhere. As this example illustrates, pilocytic astrocytoma is frequently grossly cystic. Many cystic pilocytic astrocytomas have a solid mural nodule. (D) Biphasic (cystic and solid) pilocytic astrocytoma with numerous Rosenthal fibers (arrows). These are cytoplasmic inclusions composed of GFAP (glial fibrillary acidic protein—a marker of neural glial cells), the intermediate filament protein of astrocytes. These types of tumors tend to lack signs of necrosis and mitotic figures with very limited infiltration of surrounding brain. (E) Granular eosinophilic bodies (arrows) are another cellular marker of pilocytic astrocytoma in addition to Rosenthal fibers. ([A-B] Provided by Dr. Raymond Carmody. [C-E] Provided by Dr. Dimitri P. Agamanolis.)

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INFILTRATING ASTROCYTOMAS Infiltrating astrocytomas are the most common adult primary CNS (intra-axial) tumor; they are often found in the cerebrum but can also appear in the cerebellum, brainstem, and spinal cord. These types of tumors can range from diffuse astrocytoma (grade II), to anaplastic astrocytoma (grade III), to glioblastoma (grade IV), depending on markers and their speed of proliferation (tumor aggression).

B

A

C Figure 10.2  (A) Diffuse astrocytoma MRI-FLAIR axial view of the brainstem (arrows indicating low-grade astrocytoma in temporal lobe). Diffuse astrocytomas are poorly defined and tend to not be well demarcated, but unlike pilocytic astrocytomas they can show signs of infiltration of surrounding brain but often do not enhance using gadolinium. They have a cellular density that is greater than normal white matter with GFAP staining but not as dense as the anaplastic or glioblastoma stages. (B) Diffuse astrocytoma. Low grade cellularity, no atypia or mitoses. The tumor cells show mild atypia and rare mitoses and spread in a diffuse fashion. Diffuse astrocytoma corresponds to WHO grade II. (C) Gemistocytic astrocytoma. The tumor cells are plump with a large eosinophilic cytoplasmic mass (arrows), similar to certain reactive astrocytes. This is also a WHO grade II tumor. They tend to have some nuclear pleomorphism (i.e., variability in the size, shape, and staining of cell nuclei). ([A] Provided by Dr. Raymond Carmody. [B-C] Provided by Dr. Dimitri P. Agamanolis.)

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Nolte’s The Human Brain in Photographs and Diagrams

B

A

*

C Figure 10.3  Anaplastic astrocytomas. MRI-T1 gadolinium-enhanced images of the temporal lobe as well as the midbrain of the brainstem ([A] axial view, [B] coronal view). Arrows indicate enhancing tumor in cerebral peduncle, mesial temporal lobe, and CSF spaces (extensive CSF “seeding” of tumor). The CSF spread is also causing communicating hydrocephalus. (C) Gliomatosis cerebri. Poorly differentiated glial cells infiltrate the brain and aggregate around blood vessels and neurons. Anaplastic astrocytomas demonstrate dense cellularity, have mitotic figures present demonstrating active proliferation, and have advanced nuclear pleomorphism as compared to the diffuse astrocytomas. Most anaplastic astrocytoma cases are composed of poorly differentiated glial cells, probably astrocytes, that infiltrate the brain diffusely and crowd around neurons and blood vessels (*) and under the pia. ([A–B] Courtesy Dr. Raymond Carmody. [C] Courtesy Dr. Dimitri P. Agamanolis.)

CHAPTER 10  An Introduction to Neuropathology

A

219

B Cerebral cortex Corpus callosum

Caudate Internal capsule Putamen Nucleus accumbens Temporal lobe

C

D

E

Figure 10.4  Glioblastoma (previously called glioblastoma multiforme [GBM]). (A) Grade IV, MRI-T1 with Gadolinium axial view of the tumor crossing via the corpus callosum (arrow). (B) MRI-T1 with Gadolinium sagittal view (arrow). These are aggressively growing tumors of the glial cells (i.e., astrocytes, oligodendrocytes) with recent suggestions that neural stem cells may also be a possible origin. Glioblastoma will have mitotic figures displaying rapidly dividing cells that often exhibit nearby necrosis and/or microvascular proliferation. Glioblastomas commonly exhibit a “butterfly appearance” since they can infiltrate through the white matter tracts of the corpus callosum, spreading to both hemispheres. (C) Glioblastoma of the frontal lobe. A large tumor with a variegated appearance due to necrosis and old hemorrhage (arrows). This is the basis of the term glioblastoma multiforme. Glioblastoma. (D) Viable tumor cells are arranged in a perpendicular (pseudopalisading) fashion around serpiginous necrotic areas (arrows). Glioblastoma. (E) Microvascular proliferation. The new vessels are often arranged in glomeruloid formations (arrows) and lack a blood–brain barrier. This contributes to cerebral edema and accounts for contrast enhancing in imaging studies. Glioblastomas can be stained for isocitrate dehydrogenase 1 (IDH1) as an important marker for GBM prognosis (IDH1w = poor prognosis [0.8–1.1 years]; IDH1m = better prognosis [2.0–3.8 years]). ([A-B] Provided by Dr. Raymond Carmody. [C-E] Provided by Dr. Dimitri P. Agamanolis.)

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OLIGODENDROGLIOMAS

A

D

*

C

B

* 40X

E

40X

Figure 10.5  Oligodendroglioma. (A) T1-MRI axial image of an oligodendroglioma in the right frontal cortex, (B) MRI-FLAIR image and (C) MRI-T1 with Gadolinium image (arrows). Oligodendrogliomas are subtle, slowly growing, abnormal proliferations of oligodendrocytes that can be found anywhere in the central nervous system (intra-axial), yet they are most often found in the frontal and temporal lobes of the cerebral cortex. These tumors often arise in middle-aged adults. Oligodendrogliomas are more circumscribed than astrocytomas. (D) An H&E stained biopsy of a grade II oligodendroglioma demonstrating a blue (hematoxylin stained) nucleus and the appearance of the “fried egg” in which the oligodendroglioma lacks extensions (arrows). Notice also the rich capillary network (*), another feature of this neoplasm. (E) Example of perineuronal satellitosis (the accumulation of the oligodendroglial cells encircling a neuron; arrows). This particular biopsy is classified as grade II (low grade) due to no mitotic figures observed. (Provided by Dr. Raymond Carmody.)

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EPENDYMOMAS

A

B

Vermis Colliculus Midbrain 4th Ventricle

Pons

C Medulla

D Figure 10.6  Ependymoma. (A) A sagittal MRI-T1 Gadolinium enhanced of an ependymoma within the fourth ventricle (arrow). Ependymomas typically occur in or next to the ventricular system within the brain and the central canal of the spinal cord. (B) A coronal MRI-T1 Gadolinium enhanced of the ependymoma (arrow) demonstrating the blockage of CSF fluid resulting in a noncommunicating hydrocephalus. Notice in both (A) and (B) the increased ventricle sizes. (C) Ependymoma arising from the floor of the fourth ventricle. These solid tumors tend to grow in an exophytic fashion (tending to grow outward beyond the surface epithelium from which it originates), protruding into and out of the fourth ventricle. Ependymoma. (D) Perivascular pseudorosette (arrows). A tissue pattern characteristic of ependymoma in which the tumor cell nuclei are located at some distance from a central vessel with delicate cytoplasmic processes that radiate toward the vessel wall. Nuclei of an ependymoma are round-to-oval with abundant granular chromatin. Ependymomas can be classified from grade II to IV depending on the mitotic activity, cellular density, and necrosis. ([A-B] Provided by Dr. Raymond Carmody. [C-D] Provided by Dr. Dimitri P. Agamanolis.)

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MEDULLOBLASTOMAS

B

A

C Pons

Medulla

4th ventricle

Vermis

Figure 10.7  Medulloblastoma. MRI-T1, gadolinium enhanced axial view (arrows) (A). MRI-T1 gadolinium enhanced sagittal view (B) of a medulloblastoma in the cerebellum (arrow) pushing into the brainstem. Medulloblastomas are defined as an embryonal tumor of the brain that appears in the cerebellum, often in children, but that can appear in adults as well. This malignant, intra-axial, embryonal tumor, when in the midline, often blocks CSF flow through the ventricular system, resulting in noncommunicating hydrocephalus. These tumors may spread to other parts of the CNS via the CSF. Fortunately, they are very responsive to radiation. (C) Medulloblastoma as a midline cerebellar tumor (arrows) that is necrotic following previous treatments with radiation and chemotherapy.

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Granule Cells of the Cerebellum

D Granule cells (cerebellum)

Molecular layer (cerebellum)

E

Purkinje cells (cerebellum)

F Figure 10.7 (Continued) (D) Medulloblastoma within the granular layer and extending towards the molecular layer of the cerebellum (arrows). Medulloblastomas tend to be cellularly dense (E), have hyperchromatic nuclei (arrows), and have abundant mitotic figures with high Ki67 staining. These tumors are composed of diffuse masses of small, undifferentiated oval or round cells. Medulloblastoma. (F) Homer-Wright rosettes (groups of tumor cells arranged in a circle around a fibrillary center). Similar rosettes are seen in adrenal neuroblastoma. ([A-B, D-E] Provided by Dr. Raymond Carmody. [C, F] Provided by Dr. Dimitri P. Agamanolis.)

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MENINGIOMA Typically meningiomas have round to oval nuclei, dispersed chromatin (demonstrating active proliferation) with inconspicuous nucleoli. These tumors are also graded with a range from I to III based on brain invasion and mitoses. Grade I is a more benign tumor whereas a grade III is anaplastic/malignant.

A

B Cerebral Cortex (frontal lobe)

Corpus callosum

Internal capsule

Lateral ventricle Caudate Putamen Globus pallidus (external segment) Globus pallidus (internal segment)

C Hypothalamus

Mamillary body

3rd Ventricle

Figure 10.8  Meningioma (arrow). (A) Gadolinium-enhanced T1-MRI axial. Meningiomas are typically slow-growing tumors of the epithelial cells of the meninges. These types of tumors are extra-axial (outside of the brain) and well circumscribed. (B) T2-MRI axial view. They are most often benign, hard tumors with a grayish color. Meningioma. (C) An extra-axial tumor that usually displaces brain tissue without invading the parenchyma (arrows). Notice how the ventricular system is compressed.

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D

225

E

Figure 10.8 (Continued) (D) Meningiomas have characteristic whorls in H&E stains (arrows). (E) Psammomatous meningioma. A pattern of meningioma in which tumor cells are arranged in whorls with hyalinized and calcified centers that are called psammoma (sand) bodies because they resemble tiny grains of sand (arrows). ([A-B, D] Provided by Dr. Raymond Carmody. [C, E] Provided by Dr. Dimitri P. Agamanolis.)

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DETECTION OF AN ABSCESS

*

** A

B

Figure 10.9  Abscess. Differentiating a CNS abscess from a tumor using imaging can at first be a bit tricky. (A) A T1-MRI enhanced with gadolinium demonstrating the ring-enhancing effect. A T1-MRI of an abscess will present with the central portion as being hypointense (*), with vasogenic edema surrounding the abscess (**). The wall of an abscess typically shows ring enhancement after gadolinium administration (arrow). (B) A T2-MRI demonstrating the pathology often seen with T2 imaging (arrow). The abscess center will demonstrate restricted diffusion using a DWI imaging technique (not shown), and as the abscess matures the capsule will show decreased low T2 signal. Typically abscesses are categorized into a four-stage model of disease development with the first stage of bacteria inoculation of the brain parenchyma that causes focal inflammation and edema (1 to 3 days after inoculation). On days 4 to 9 there is neutrophil accumulation, edema, and some tissue necrosis. Macrophages and lymphocytes predominate in the infiltrate. The third stage (days 10 to 14) is characterized by the development of a capsule that is vascularized and ring enhancing. In the fourth stage, the host immune response causes the capsule to wall off with destruction of surrounding healthy brain tissue in an attempt to sequester the infection. (Provided by Dr. Raymond Carmody.)

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DEMYELINATING SYNDROMES Demyelinating diseases of the central nervous system affect the oligodendrocytes. These types of disease are characterized by damage to the myelin (i.e., white matter) with preservation of the neuron itself, resulting in difficulties in conduction properties. There are many different types of infections that may cause the loss of myelin, while in some cases the immune system itself may attack the myelinating cells of the nervous system.

B A Posterior column Dorsal horn (Substantia gelatinosa) Lateral funiculus Ventral horn

C

Spinothalamic tract

D Figure 10.10  Multiple sclerosis (MS), a common demyelinating disease, is a CNS autoimmune demyelinating disorder that (A) presents with multiple lesions (often lateral to the ventricles, arrows) that are typically well circumscribed but often irregular in shape and referred to as plaques (MRI-FLAIR sagittal view). Clinical features include distinct episodes that may wax-and-wane over time. In the case of MS, autoantibodies attack components of the myelin made by oligodendrocytes in which distinct gray-tan spots in normally white matter tract areas within the CNS are observed. MS. (B) Periventricular plaques. MS plaques are randomly distributed (arrows). They have a predilection for the periventricular white matter, optic nerves, and spinal cord but spare no part of the CNS. MS of the spinal cord. (C) The pale lesions are plaques (arrows). The deep blue areas are normal myelin. Unlike neurodegenerative (ALS) or nutritional disorders (subacute combined degeneration), plaques have an irregular anatomical distribution. (D) Perivascular lymphocytes in an active MS plaque (arrows). In the acute phase (active plaque), activated mononuclear cells, including lymphocytes, microglia, and macrophages destroy myelin and, to a variable degree, oligodendrocytes. ([A] Provided by Dr. Raymond Carmody. [B-D] Provided by Dr. Dimitri P. Agamanolis.)

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Progressive multifocal leukoencephalopathy (PML) is a deadly demyelinating disease of the CNS due to lytic infection of oligodendrocytes by the ubiquitous opportunistic polyomavirus JC (JCV). Most persons acquire this virus at a young age but the virus remains latent. The virus is reactivated when cellular immunity is suppressed. Most PML cases occur in patients with AIDS, cancer,

inflammatory disorders, and organ transplant recipients due to suppressive-immune medications. PML presents clinically as a variety of neurologic deficits (visual loss, paralysis, dementia) evolving rapidly towards death. Unlike MS, inflammation is minimal in PML.

Gray-white border

4th Ventricle Gray matter

A

White matter

Middle cerebellar peduncle

Cerebellum (lack of white matter)

Inferior cerebellar peduncle

B Pons

C Figure 10.11  (A) Progressive multifocal leukoencephalopathy (PML) myelin stain. PML begins with small demyelinative foci at the cortex-white matter junction (arrows). Confluence of these foci results in large irregular white matter lesions that involve the cerebrum, cerebellum, and brainstem. PML. (B) Demyelination of the cerebellum and pons (arrows). PML. (C) Enlarged homogeneous oligodendrocyte nucleus with inclusion (arrow). The nuclei of infected oligodendrocytes are packed with viral particles that cause them to enlarge and have a ground glass appearance. (Provided by Dr. Dimitri P. Agamanolis.)

CHAPTER 10  An Introduction to Neuropathology Central Pontine Myelinolysis (CPM) is characterized as a loss of myelin on neurons within the base and tegmentum of the pons of the brainstem. Although the name suggests that this occurs only in the pons, it can also be extended to the cerebellum, cerebrum, and spinal cord (extrapontine myelinolysis). There is loss of myelin while axons are typically spared with very little to no inflammation.

A

229

Clinically, symptoms can vary from no symptoms to severe cases in which there can be spastic bulbar paralysis, quadriplegia, stupor, coma, or the locked-in syndrome. CPM is often caused by fluid and electrolyte imbalance precipitated by a rapid electrolyte influx in hyponatremia patients. CPM can be regarded as an osmoticinduced demyelination syndrome.

B

Figure 10.12  (A) MRI-T2 FLAIR axial view of a patient with central pontine myelinolysis (CPM) and the loss of the brainstem tissue (arrow). CPM. (B) CPM is a degeneration of a symmetrical midline patch of the basis pontis (arrows). There is loss of myelin and less severe loss of axons. Neurons of the nuclei pontis are relatively spared. No inflammation is seen. There is no selective involvement of fiber systems. ([A] Provided by Dr. Raymond Carmody. [B] Provided by Dr. Dimitri P. Agamanolis.)

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NEURODEGENERATIVE DISEASES Alzheimer Disease (AD) is the most common cause of global dementia that can be diagnosed based on the accumulation of two proteins—amyloid-Aβ and tau. Typically the likelihood of AD diagnosis is based on cognitive impairment over time along

A

with CNS imaging. On imaging studies, the degree of cortical atrophy, based on expansion of sulci and enlargement of the ventricles (ex vacuo hydrocephalus), can be used along with clinical signs to make the diagnosis. Moreover, imaging studies are used to rule out treatable causes of dementia, such as unsuspected tumor.

B Longitudinal fissure

Frontal cortex Lateral ventricle

Caudate Putamen

Nucleus accumbens Temporal lobe

C Optic chiasm Figure 10.13  Alzheimer Disease (AD). (A) CT scan, axial view of a patient with AD demonstrating large sulci and ventricles. (B) Cortical atrophy in advanced AD. Notice the larger than normal sulci and reduced size of gyri. AD. (C) Cortical atrophy and dilatation of the lateral ventricles due to loss of brain tissue (hydrocephalus ex vacuo).

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D

231

E

F Figure 10.13 (Continued) AD. (D) Beta amyloid immunostain reveals a myriad of plaques in the cerebral cortex (arrows). Vascular amyloid is also present. AD. (E) Neurofibrillary tangle and neuritic plaque. Bielschowsky silver stain. There are two main lesions in AD: senile plaques (also called Alzheimer plaques, neuritic plaques) and neurofibrillary tangles. Neuritic plaques are amyloid deposits containing degenerating neuronal processes with tau paired helical filaments (arrows). AD. (F) Two senile plaques and multiple neurofibrillary tangles (the small dark objects around the plaques). Bielschowsky silver stain. ([A] CT image provided by Dr. Raymond Carmody. [B-F] Provided by Dr. Dimitri P. Agamanolis.)

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Plaques are characterized as aggregates of Aβ peptide within the neuropil, while tangles are aggregates of tau, a microtubule binding protein. The amyloid Aβ protein within a plaque can be stained using Congo red and viewed under polarized light. The NFTs are tau-containing bundles of filaments that surround the nucleus of the neurons. Within the pyramidal cells they give a “flame-like” appearance using a silver stain and immunohistochemistry towards tau protein.

Parkinson Disease (PD) is a neurodegenerative disease that results in a decrease in the initiation of movements and a resting tremor. It is characterized by a loss of the dopaminergic neurons of the substantia nigra (in the midbrain of the brainstem). The confirmation of the diagnosis upon autopsy is the whiteness (pallor) of the substantia nigra (Latin for black substance).

Aqueduct Superior colliculus

Periaqueductal gray

Red nucleus Substantia nigra Cerebral peduncle PD

A

B

Normal

Dopaminergic containing neurons of the SN

C

PD

D

Normal

E Figure 10.14  Parkinson disease (PD) (A) and (B) normal. Depigmentation of the substantia nigra (SN) of the zona compacta in PD (arrow) (A). Normal SN (arrow) (B). The pathology of PD affects the dopamine-producing neurons of the SN. In advanced PD, loss of pigmented neurons results in gross depigmentation of the SN. Micro of PD pathology (C) and (D) normal. The mid-section of the SN (zonal compacta) is involved earliest and most severely. Loss of SN neurons in the zona compacta (C). Normal SN in the same area (D). PD. (E) Lewy body in an SN neuron. The melanin granules are red-brown. The key pathology in PD is α-synuclein accumulation. Lewy bodies are large α-synuclein aggregates in the neuronal body forming round lamellated eosinophilic cytoplasmic inclusions (arrow). (Provided by Dr. Dimitri P. Agamanolis.)

CHAPTER 10  An Introduction to Neuropathology Huntington Disease (HD) is an autosomal dominant disease characterized by the progressive loss of selective neurons in the basal ganglia. Unlike in PD, patients with HD experience more erratic, hyperkinetic movements. HD is due to a polyglutamine trinucleotide repeat expansion in which the protein, huntingtin, is made with an excess of glutamine that can result in protein

233

aggregation and neuronal loss. Protein aggregates of huntingtin can be found in neurons of the striatum. On CT or MR imaging there is prominent atrophy of the caudate nucleus with secondary atrophy of the putamen and clear signs of lateral ventricular expansion (hydrocephalus ex vacuo).

Lateral ventricle Lateral ventricle Internal capsule Putamen Putamen

Globus pallidus

Anterior commissure

A

B

Figure 10.15  Huntington disease control. (A) Normal caudate nuclei (arrow), small lateral ventricles. (B) Huntington disease. Gross examination of the brain reveals atrophy of the caudate nucleus (arrow) and putamen and dilatation of the anterior horns of the lateral ventricles, which are obvious on MRI in advanced cases. (Provided by Dr. Dimitri P. Agamanolis.)

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Amyotrophic lateral sclerosis (ALS) is a progressive disease that affects both the upper and lower motor neurons, resulting in the denervation of muscle and the advance of weakness over time. ALS is thought to be caused by the accumulation of toxic proteins. At autopsy patients with ALS have a lack of gray matter in the anterior horns of the spinal cord, as well as atrophy of the precentral (primary motor cortex) gyrus.

A

B Posterior columns Dorsal horn Lateral funiculus

Atrophy of the muscle fascicle

Anterior horn

C D Figure 10.16  Amyotrophic lateral sclerosis (ALS). (A) MRI-T2, (B) MRI-T2 FLAIR axial views in the loss of motor fibers running though the descending corticospinal tract of the cerebral peduncle (arrows). ALS. (C) Degeneration of the corticospinal tracts (arrows) (the axons of the upper motor neurons). Myelin stain. In ALS there is also degeneration and loss of motor neurons in the anterior horns of the spinal cord and motor nuclei of the brainstem (not illustrated in this picture). Remaining neurons will contain eosinophilic cytoplasmic inclusions called Bunina bodies (remnants of vacuoles) (not illustrated here). (D) Muscle, ALS. Denervation atrophy indicating chronic denervation. ([A-B] Images provided by Dr. Raymond Carmody; [C-D] Provided by Dr. Dimitri P. Agamanolis.)

G LO S S A RY

This glossary provides brief descriptions and definitions of the neuroanatomical structures labeled in the preceding chapters (except for the bones and muscles indicated in Chapter 9). Within each entry, terms discussed further in their own entries elsewhere in the glossary are italicized. Although these definitions were written specifically for this atlas, many are adapted from passages in Nolte’s The Human Brain, seventh edition.a Some others derive, with modifications, from a text by Jay B. Angevine Jr. (with Carl W. Cotman), Principles of Neuroanatomy.b We thank Jeffrey House of Oxford University Press for permission to draw on the latter source. We have illustrated most of the glossary terms, placing adaptations of figures from the atlas and some from Nolte’s The Human Braina after relevant entries. Space did not permit doing this for all entries, however, so alternative terms that may be consulted for an illustration are indicated by an asterisk (*).

Accessory nerve.  The 11th cranial nerve, which emerges laterally from the upper cervical spinal cord and innervates the sternocleidomastoid and trapezius muscles to mediate turning the head and elevating the shoulder. (The accessory nerve used to be described as having both cranial and spinal parts. The spinal part corresponded to the accessory nerve as defined here, and the cranial part to a series of rootlets that emerge laterally from the caudal medulla, join the vagus nerve, and run to the palate, pharynx, and larynx.)

CN VI

Abducens nerve.  The 6th cranial nerve, which emerges anteriorly from the brainstem between the pons and medulla. It innervates the lateral rectus of the ipsilateral eye, producing abduction (hence its name). Internal genu (facial nerve)

MLF

Accessory nucleus.  A column of motor neurons for the ipsilateral sternocleidomastoid and trapezius, extending from the midcervical spinal cord into the caudal medulla.

Medial lemniscus

Abducens nerve fibers

Abducens nucleus.  Contains the motor neurons for the ipsilateral lateral rectus, as well as interneurons that project through the contralateral medial longitudinal fasciculus (MLF) to medial rectus motor neurons. Activating the motor neurons and interneurons simultaneously provides for conjugate horizontal eye movements.

CN XI fibers

C3 a

Nolte J: The human brain, ed 9, Philadelphia, 2009, Mosby Elsevier. Angevine JB Jr, Cotman CW: Principles of neuroanatomy, New York, 1981, Oxford University Press. b

Alveus.  A layer of white matter on the ventricular surface of the hippocampus*, mostly conveying hippocampal efferents. 235

236

Glossary

Ambient cistern. The combination of the superior cistern and sheetlike extensions from it that partially encircle the midbrain.

supplying gyrus rectus and orbital gyri, the medial surface of the frontal and parietal lobes, and an adjoining narrow band of cortex along their superior surfaces.

Provided by Dr. Elena Plante, University of Arizona

Amygdala.  A collection of nuclei in the anteroinferior part of the limbic lobe, just beneath the uncus, forming the core of one of the two major limbic circuits. (The core of the other is the hippocampus.)

Anterior choroidal artery.  A long, thin branch of the internal carotid artery that accompanies the optic tract and supplies many structures along the way: the optic tract, choroid plexus of the inferior horn of the lateral ventricle, part of the cerebral peduncle, deep regions of the internal capsule, and parts of the thalamus and hippocampus. The anterior choroidal artery is a particularly large example of the numerous penetrating arteries that arise from all arteries around the base of the brain and supply nearby deep structures.

Hippocampus

Angular gyrus.  The part of the inferior parietal lobule* formed by the cortex surrounding the upturned end of the superior temporal sulcus; although variable in size and shape, this region (usually on the left) is important in language functions. Ansa lenticularis.  Part of the projection from the globus pallidus to the thalamus. It has fewer axons than the other part (the lenticular fasciculus). It forms a compact, conspicuous cable of myelinated fibers running beneath the internal capsule and hooking around its medial edge.

Anterior commissure.  A small, sharply defined bundle of commissural fibers just beneath and behind the rostrum of the corpus callosum, to which it is closely related developmentally. A few inconspicuous anterior fibers interconnect olfactory structures, whereas the million or so posterior fibers interconnect the two temporal lobes. Fornix

Interventricular foramen

Anterior cerebral artery.  The more anterior of the two terminal branches of the internal carotid artery (the other being the middle cerebral artery). It curves around the corpus callosum with branches

Anterior communicating artery. A short vessel at the anterior end of the circle of Willis interconnecting the two anterior cerebral arteries just anterior to the optic chiasm; a common site of aneurysm formation.

Glossary

237

cerebellum, including the flocculus, and lateral parts of the caudal pons; often referred to by the acronym AICA. Posterior cerebral a. Superior cerebellar a. Basilar

Anterior corticospinal tract.  The smaller of the two corticospinal tracts. It consists of the fibers (about 15%) in each medullary pyramid that continue directly into the anterior funiculus of the spinal cord without decussating; many fibers eventually cross in the anterior white commissure of the cord before terminating, but some end ipsilaterally. Fibers of the anterior corticospinal tract end (mainly in the cervical and thoracic spinal cord) on spinal motor neurons or nearby interneurons.

Anterior funiculus.  One of the three major divisions of the spinal white matter, the others being the lateral and posterior* funiculi. (Funiculus is Latin for “string” or “cord,” as in the term “funicular” for “cable car.”) The anterior funiculus is located between the anterior median fissure and the exiting ventral roots and contains various tracts (mostly descending), including the anterior corticospinal tract. Anterior horn.  One of the three general divisions of the spinal gray matter, the others being the posterior horn and the intermediate gray; contains numerous local-circuit neurons, cell bodies of alpha motor neurons, axons of which enter ventral roots and end on skeletal muscle, and cell bodies of gamma motor neurons that regulate muscle spindles.

PICA Vertebral a.

Anterior nucleus. See thalamus*. Anterior perforated substance.  The inferior surface of the forebrain, roughly between the orbital gyri and the hypothalamus. So named because numerous lenticulostriate and other small penetrating branches enter the brain here.

Anterior root. See ventral root*. Anterior spinal artery. A single midline vessel that originates rostrally as two arteries (one from each vertebral artery), which shortly join and then course within the anterior median fissure along the entire spinal cord. It receives additional blood from the thoracic/abdominal aorta through numerous anastomoses with radicular arteries below the upper cervical region and gives rise to hundreds of central and circumferential branches that supply the anterior two thirds of the cord.

Motor neurons

Anterior inferior cerebellar artery.  A long, circumferential branch of the basilar artery arising just above the union of the two vertebral arteries. It supplies anterior regions of the inferior surface of the

Provided by Dr. Norman Koelling, University of Arizona

238

Glossary

Anterior spinocerebellar tract.  Crossed fibers from lumbosacral spinal gray matter, carrying mechanoreceptive and other information related to leg movement. The anterior spinocerebellar tract stays in a lateral position along the spinal cord and brainstem until the rostral pons and there moves over the superior cerebellar peduncle and enters the cerebellum, where it largely recrosses before terminating.

Arachnoid. The middle layer of the three layers of meninges, named for its cobweb-like appearance. The arachnoid is loosely adherent to the dura mater and connected to the pia mater by fine strands of connective tissue (arachnoid trabeculae). The resulting subarachnoid space, between arachnoid and pia, provides a route for the distribution of blood vessels and the flow of cerebrospinal fluid over the surface of the CNS.

T10

Anterior white commissure.  A thin sheet of spinal white matter between the central canal and the anterior median fissure, providing a route for fibers such as those of the spinothalamic tract to cross the midline in the spinal cord.

Anterolateral system.  An umbrella term for the spinothalamic tract and closely related ascending fibers, all of which deal with pain, temperature, and to some extent tactile/pressure sensation. Many do not reach the thalamus, ending instead at higher spinal levels and/or in brainstem sites such as the reticular formation. Aqueduct (of Sylvius). The narrow channel (a remnant of the lumen of the embryonic mesencephalon) through the midbrain connecting the third and fourth ventricles. The aqueduct lacks choroid plexus and serves only as a conduit for cerebrospinal fluid descending through the ventricular system (its stenosis or obstruction is the most common cause of congenital hydrocephalus). Third ventricle Pineal gland Superior & inferior colliculi

Fourth ventricle

Arachnoid granulations

Arachnoid granulations. Small evaginations of the arachnoid* protruding through a hiatus in dural connective tissue into the lumen of a dural sinus of the brain (especially the superior sagittal sinus), so that only loosely arranged arachnoid cells and endothelium intervene between subarachnoid space and venous blood. Arachnoid granulations are the major (but not exclusive) sites of reabsorption of cerebrospinal fluid into the venous system. Area postrema. A small region at the caudal end of the fourth ventricle where the ventricular walls join at the obex. The area postrema is one of several circumventricular organs of the brain where cerebral capillaries are fenestrated and allow free communication between the blood and brain extracellular fluid (“holes” in the blood-brain barrier); it is thought to monitor blood for toxins and to trigger vomiting. Basal forebrain.  A loosely used umbrella term for an area at and near the inferior surface of the cerebrum between the hypothalamus and orbital gyri. It includes the anterior perforated substance superficially and extends superiorly into the septal nuclei and the adjacent oxymoronically named substantia innominata (see also basal nucleus).

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Glossary Basal ganglia. A group of subcortical nuclei, most prominently including the striatum, globus pallidus, substantia nigra, and subthalamic nucleus, that collectively modulate the output of frontal cortex. Basal ganglia damage has traditionally been thought to cause disorders characterized by involuntary movements, difficulty initiating movement, and alterations in muscle tone (e.g., Parkinson’s disease). However, damage to certain parts of the basal ganglia can cause disturbances of cognition and motivation instead. Subthalamic nucleus Striatum

Great cerebral vein

Basilar artery.  A large vessel formed by union of the two vertebral arteries. The basilar artery runs upward along the anterior median surface of the pons and gives rise to many branches that supply the pons, superior surface of the cerebellum, and caudal midbrain; it bifurcates at the level of the midbrain into the two posterior cerebral arteries.

Posterior cerebral a. Superior cerebellar a.

Globus pallidus

Substantia nigra

AICA PICA

Basal nucleus (of Meynert).  Groups of large cholinergic neurons in the substantia innominata of the basal forebrain. Widespread projections of these and nearby septal neurons blanket the neocortex, hippocampus, and amygdala with cholinergic endings, suggesting that it plays a role in general regulation of cerebral activity.

Vertebral a.

Brachium of the inferior colliculus.  Auditory afferents from the inferior colliculus on their way to the medial geniculate nucleus. Inferior colliculus

Basal pons.  A mass of gray and white matter, straddling the anterior surface of the pons and filled with transversely and longitudinally coursing fibers. The basal pons looks like a bridge (thus the name pons, which is Latin for bridge) between the two cerebellar hemispheres, but in fact it is a key link between the cerebrum and cerebellum: Corticopontine fibers end in its scattered pontine nuclei, which in turn give rise to pontocerebellar fibers that project across the midline and enter the cerebellum via the middle cerebellar peduncle.

Medial geniculate nucleus Pontine nuclei Middle cerebellar peduncle

Brachium of the superior colliculus.  A bundle of fibers that passes over the medial geniculate nucleus to reach the superior colliculus. Contains afferents from the retina directly to the superior colliculus and pretectal area, as well as projections from cerebral cortex to the superior colliculus and from the superior colliculus to the pulvinar. Superior colliculus To pulvinar

Pontocerebellar fibers

Corticopontine & corticospinal fibers

Basal vein (of Rosenthal).  A deep cerebral vein whose tributaries drain the insula and some structures near the inferior surface of the forebrain. The basal vein then curves around the midbrain and joins the great cerebral vein.

MGN

From retina, visual cortex

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Glossary

Brainstem. In common medical usage, the midbrain, pons, and medulla. (Earlier definitions sometimes included various parts of the diencephalon and telencephalon as well [e.g., thalamus, basal ganglia].)

Central canal.  The narrow, functionless vestige of the lumen of the spinal part of the embryonic neural tube, lined by ependyma and usually obstructed by epithelial debris. It runs the length of the spinal cord, contains traces of cerebrospinal fluid, and opens into the fourth ventricle at the obex of the medulla.

n

brai

Mid

s

Pon

lla du Me

Calcarine sulcus.  A prominent, deep cerebral infolding. It originates anteriorly in the temporal lobe near the splenium of the corpus callosum and continues posteriorly into the occipital lobe, where it terminates near the occipital pole. Its upper and lower banks contain the primary visual cortex. Anteriorly along this course, the parietooccipital sulcus branches off from it. Parietooccipital sulcus

Callosomarginal artery.  A branch of the anterior cerebral artery that follows the cingulate sulcus. Cauda equina.  A collection of dorsal and ventral roots, named for their collective resemblance to a horse’s tail, descending from the caudal end of the spinal cord (at about vertebral level L1/L2) to the intervertebral foramina at which they exit the vertebral canal. Filum terminale

Conus medullaris

Provided by Dr. Norman Koelling, University of Arizona

Caudate nucleus.  The more medial part of the striatum*, bulging into the lateral ventricle with its large head in the wall of the anterior horn, tapering body immediately behind, and long slender tail running posteriorly into the atrium and then anteriorly into the inferior horn. It is principally connected with prefrontal and other association areas of the cortex and is involved more in cognitive functions and less directly in movement.

Central sulcus (of Rolando). An anatomically and functionally important infolding of the cerebral hemisphere, beginning just medial to its superior border, proceeding over its superior margin, and descending obliquely forward almost to the lateral sulcus. The central sulcus is the boundary between frontal and parietal lobes and the transition zone between primary motor and primary somatosensory cortex.

Central tegmental tract.  A complex, heterogeneous tract running centrally through each side of the brainstem reticular formation and providing a major highway through which reticular afferents and efferents are distributed. It also contains a major projection from the red nucleus to the inferior olivary nucleus, axons intrinsic to the reticular formation, and undoubtedly other types of fibers that are not yet fully characterized.

Glossary Centromedian nucleus. See thalamus*. Cerebellar cortex.  The extensively folded, three-layered sheet of gray matter that covers the cerebellum. Granular layer.  The deepest layer, adjacent to the cerebellar white matter. Named for the enormous number of tiny granule cells that occupy it: about half of all the neurons in the CNS live in this layer. Molecular layer.  The most superficial layer, containing relatively few neurons. Mainly a layer in which the axons of granule cells and other cerebellar interneurons synapse on Purkinje cell dendrites. Purkinje cell layer.  A layer of relatively large neurons whose axons provide the output from cerebellar cortex.

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Tonsil.  A medial, inferior part of the posterior lobe hemisphere, adjacent to the medulla as it passes through the foramen magnum. Vermis (Latin for “worm”).  The most medial zone of the cerebellum, straddling the midline. Extends through the anterior, posterior, and flocculonodular lobes. Hemisphere: anterior lobe posterior lobe

Vermis: anterior lobe nodulus posterior lobe

Molecular Purkinje cells

Tonsil

Flocculus

Granular Primary fissure

Vermis (anterior lobe)

White matter Provided by Dr. Nate McMullen, University of Arizona

Cerebellothalamic fibers.  Efferent fibers from the deep cerebellar nuclei (mainly the dentate nucleus) that pass via the superior cerebellar peduncle and its decussation through or around the contralateral red nucleus* to the ventral lateral nucleus of the thalamus (VL), which in turn projects to motor areas of cortex. This tract completes a long, doubly crossed circuit between each cerebral hemisphere and the contralateral cerebellar hemisphere that is crucial for the planning and coordination of skilled movements. Because most of these fibers arise in the dentate nucleus, they are sometimes referred to as the dentatothalamic tract. Cerebellum.  A large, convoluted subdivision of the nervous system (cerebellum literally means “little brain”) that receives input from sensory systems, the cerebral cortex, and other sites and participates in the planning and coordination of movement. Anterior lobe. All of the cerebellum anterior to the primary fissure (partly vermis, partly hemisphere). Flocculus.  The hemispheral component of the flocculonodular lobe, the part of the cerebellum particularly concerned with the vestibular system and eye movements. Hemispheres. The large paired lateral parts, important for coordination of the limbs. Nodulus.  The vermal component of the flocculonodular lobe, the part of the cerebellum particularly concerned with the vestibular system and eye movements. Posterior lobe.  All of the cerebellum, except for the flocculonodular lobe, posterior to the primary fissure (partly vermis, partly hemisphere). Primary fissure.  Separates the anterior and posterior lobes of the cerebellum.

Vermis (posterior lobe)

Tonsil

re he be) isp r lo m io He ster o (p

Vermis (nodulus)

Cerebral peduncle.  As the term is used in this book, a massive bundle of tightly packed corticospinal, corticobulbar, and corticopontine fibers traveling along the base of the midbrain. (Others use the term cerebral peduncle to refer to all of one side of the midbrain inferior to the aqueduct. In this terminology, the bundle of corticofugal fibers is called the pes pedunculi, basis pedunculi, or crus cerebri.)

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Glossary

Choroid fissure.  A C-shaped fissure on the medial surface of each cerebral hemisphere, leading into the choroid plexus of each lateral ventricle. Because of this C shape, coronal sections often cut through the choroid fissure in two places. Choroid plexus

Cingulate sulcus.  A more or less continuous, curved infolding of each cerebral hemisphere clearly demarcating the outer margin of the cingulate gyrus*; posteriorly a branch (the marginal branch) ascends to the superior surface of the parietal lobe immediately behind the upper end of the central sulcus. Cingulum. An association bundle located in the white matter underlying the cingulate gyrus and interconnecting limbic cortical areas. Circle of Willis.  The anastomotic arterial polygon at the base of the brain, consisting of parts of the internal carotid, anterior cerebral, and posterior cerebral arteries, interconnected by the anterior and posterior communicating arteries.

Choroid plexus.  Long, highly convoluted, vascularized strands in the lateral, third, and fourth ventricles that produce most of the cerebrospinal fluid. Choroidal vein.  A tortuous vessel that joins the terminal (thalamostriate) vein near the interventricular foramen and drains the choroid plexus of the body of the lateral ventricle.

Cisterna magna.  A large subarachnoid cistern between the medulla and the inferior vermis. Also referred to as the cerebellomedullary cistern.

Provided by Dr. Elena Plante, University of Arizona

Cingulate gyrus. A broad belt of cortex partially encircling the corpus callosum. The cingulate gyrus forms the upper part of the limbic lobe, continuing through a narrow isthmus into the parahippocampal gyrus. It has extensive limbic connections, particularly in cortical circuits leading ultimately to or from the hippocampus. Marginal branch

Cingulate sulcus

Clarke’s nucleus (nucleus dorsalis). A rounded group of large cell bodies in the intermediate gray of the spinal cord near the medial edge of the base of the posterior horn, from about T1 through L2 or L3. Clarke’s nucleus is the origin of the posterior spinocerebellar tract, through which stretch receptor and other mechanoreceptive input from the leg reaches the ipsilateral cerebellar vermis and medial part of the cerebellar hemisphere.

Glossary Claustrum.  A thin but extensive layer of gray matter beneath the insula, separated from it and the underlying putamen by the extreme and external capsules respectively. The claustrum has reciprocal connections with cerebral cortex, but incompletely understood functions. External & extreme capsules

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internal capsule (immediately anterior to the closely related corticospinal fibers) to terminate (via numerous, often intricate routes) in the “bulb” (an old term for the medulla or, by extension, for the entire brainstem) on neurons of sensory relay nuclei, the reticular formation, and motor nuclei of cranial nerves. In common usage, the term refers only to the last fibers of this group. Basically the equivalent of the corticospinal tract for cranial nerve nuclei. Corticopontine tract.  A very large collection of fibers originating in the frontal, parietal, occipital, temporal, and even limbic lobes and descending through the internal capsule (anterior and posterior to the corticospinal/corticobulbar projections) to pontine nuclei of the basal pons*, from which axons pass to the contralateral half of the cerebellum through the middle cerebellar peduncle.

Cochlear nuclei.  The nuclei in which the primary auditory afferents of the vestibulocochlear nerve terminate. The dorsal and ventral cochlear nuclei form a continuous band of gray matter draped over the inferior cerebellar peduncle* near the pontomedullary junction and project bilaterally to the superior olivary nucleus and into the lateral lemniscus. Collateral sulcus.  A deep infolding of the inferior surface of the temporal lobe*, bulging into the wall of the inferior horn of the lateral ventricle as the collateral eminence. It separates the occipitotemporal (fusiform) gyrus from the parahippocampal gyrus.

Corticospinal tract. A collection of about a million axons that originate in the cerebral cortex, descend through the internal capsule, cerebral peduncle, basal pons, and medullary pyramid, then reach the spinal cord, where they terminate, via the lateral and anterior corticospinal tracts. Roughly a third of them originate in primary motor cortex, the rest arising from premotor and supplementary motor areas and the parietal lobe (especially somatosensory cortex). Corticospinal axons end in the spinal cord on cells of the posterior horn, intermediate gray, and anterior horn, where some synapse directly on alpha and gamma motor neurons. Although the corticospinal tract has multiple functions, the principal one is mediating voluntary movements. Cuneate tubercle. A swelling on the dorsolateral aspect of the lower medulla overlying nucleus cuneatus, which contains the cells of origin of the part of the medial lemniscus carrying tactile and proprioceptive information from the arm and upper body.

Conus medullaris.  The pointed caudal end of the spinal cord, at about vertebral level L1/L2, beyond which the pial covering of the spinal cord continues as the filum terminale, surrounded by the cauda equina*. Corpus callosum.  Latin for “hard body,” a massive curvilinear bridge of commissural fibers, shaped in sagittal sections like an overturned canoe. The corpus callosum interconnects most cortical areas of the two cerebral hemispheres and serves to join them functionally, providing an important substrate for a unitary consciousness. Body.  The main arched part of the corpus callosum. Its fibers distribute extensively within each hemisphere. Genu.  The kneelike sharp anterior bend, containing fibers to and from the frontal lobes. Rostrum.  The slender, narrow part beneath the genu, resembling the prow of the (overturned) boat; interconnects orbital gyri. Splenium. The thick, rounded posterior bend (like a rolled bandage, for which it was named), containing fibers to and from the occipital and temporal lobes. Genu

Body

Cuneus. The wedge-shaped area of the medial surface of the occipital lobe between the calcarine and parietooccipital sulci. Includes the upper half of primary visual cortex and parts of visual association cortex.

Splenium

Rostrum

Corticobulbar tract.  Strictly defined, a large collection of fibers originating in the cerebral cortex and descending through the

Dentate nucleus.  The largest and most lateral of the deep cerebellar nuclei, featuring a highly convoluted narrow band of neurons arranged like a bag, with an anteriorly directed opening (hilus)

244

Glossary

from which efferents emerge to form most of the superior cerebellar peduncle.

Decussation of superior cerebellar peduncles

Superior cerebellar peduncle

Dorsal raphe nucleus. See raphe nuclei. Denticulate ligament.  A thickened, lateral, serrated sheet of pia mater on each side of the spinal cord, with periodic extensions that attach to the arachnoid and dura mater, supporting the weight and stabilizing the position of the cord within the dural sac.

Dorsal root.  The posterior (sensory) root of a spinal nerve, which divides into a variable number of regularly spaced rootlets that enter the spinal cord along its posterolateral sulcus. Ventral root

Spinal dura and arachnoid Provided by Dr. Norman Koelling, University of Arizona

Diencephalon.  Literally the “in-between brain,” the caudal subdivision of the embryonic forebrain, giving rise to the pineal gland, habenula, thalamus, subthalamic nucleus, retina, optic nerve and tract, hypothalamus, infundibulum (pituitary stalk), and posterior lobe of the pituitary gland. Dorsal cochlear nucleus. See cochlear nuclei. Dorsal longitudinal fasciculus.  Ascending and descending fibers connecting the hypothalamus directly and indirectly to visceral sensory neurons and preganglionic autonomic neurons, traveling through the periaqueductal and periventricular gray matter.

Dorsal motor nucleus of the vagus.  A prominent autonomic efferent nucleus containing most of the preganglionic parasympathetic neurons for thoracic and abdominal viscera.

Provided by Dr. Norman Koelling, University of Arizona

Dorsomedial nucleus (DM). See thalamus*. Dura mater.  The outermost of the three layers of meninges, providing critical mechanical support for the CNS. Cranial dura mater is continuous with the periosteum of the inner surface of the skull, whereas in the vertebral canal it forms a dural sac within which the spinal cord is suspended by denticulate ligaments*. Edinger-Westphal nucleus.  A column of small nerve cell bodies near the midline of the oculomotor nucleus. Its neurons form the efferent limb of the direct and consensual pupillary light reflexes, through which preganglionic parasympathetic neurons (via postganglionic neurons in the ciliary ganglion) cause contraction of the pupillary sphincter. Also part of the efferent limb of the near reflex, through which it causes (again via postganglionic neurons in the ciliary ganglion) ciliary muscle contraction to thicken the lens and pupillary constriction to increase depth of focus.

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Glossary Entorhinal cortex. The cortex covering the anterior part of the parahippocampal gyrus, near the uncus. Entorhinal cortex receives inputs from the amygdala, olfactory bulb, the limbic lobe, and other cortical areas and in turn is the major source of afferents to the hippocampus.

preganglionic parasympathetic axons for submandibular, sublingual, and lacrimal glands. CN VII

CN VIII

(motor root)

CN VII (intermediate nerve)

External capsule.  A thin layer of white matter interposed between the claustrum* and putamen, containing association fibers that interconnect various cortical areas and modulatory fibers from sites such as the basal nucleus. External medullary lamina (of the thalamus).  A thin, curved sheet of myelinated fibers (afferent and efferent), in places reticulated and in others dense, surrounding the lateral surface of the thalamus*; enclosed by a thin shell of gray matter, the reticular nucleus, which intervenes between it and the internal capsule. Extreme capsule.  A thin layer of white matter interposed between the claustrum* and insula. The extreme capsule is the subcortical white matter of the insula but also contains association fibers that interconnect various other cortical areas.

CN VI

Provided by Dr. Norman Koelling, University of Arizona

Facial nucleus.  A group of motor neurons in the caudal pontine tegmentum that innervate muscles of the ipsilateral half of the face. Their axons loop around the abducens nucleus in the internal genu of the facial nerve, forming the facial colliculus* in the floor of the fourth ventricle, before leaving the brainstem. Fasciculus cuneatus. Uncrossed, large, myelinated, primary afferents entering the posterior column of the spinal cord rostral to T6 and carrying tactile and proprioceptive information from the ipsilateral arm; many of these fibers ascend to the medulla to terminate in nucleus cuneatus. Fasciculus gracilis

Fasciculus cuneatus

Facial colliculus.  A swelling in the floor of the fourth ventricle, caused by the underlying internal genu of the facial nerve looping around the abducens nucleus.

Facial nerve

Internal genu

Fasciculus gracilis.  Uncrossed, large, myelinated, primary afferents entering the posterior column of the spinal cord caudal to T6 and carrying tactile and proprioceptive information from the ipsilateral leg; many of these fibers ascend to the medulla, medial to fasciculus cuneatus*, to terminate in nucleus gracilis. Facial nucleus

Abducens nucleus

Facial nerve.  The 7th cranial nerve, which emerges anterolaterally from the brainstem along the groove between the basal pons and the medulla. Motor root. Large, medial root containing axons of motor neurons for muscles of facial expression. Sensory root (intermediate nerve).  The smaller of the two roots, emerging between the motor root and the vestibulocochlear nerve, containing afferents from taste buds, nasopharyngeal mucous membranes, and skin of the outer ear, as well as

Fastigial nucleus.  The most medial of the deep cerebellar nuclei. Its afferents come mainly from the cerebellar vermis, and its efferents project bilaterally to the vestibular nuclei and reticular formation.

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Glossary

Filum terminale.  A thin strand of connective tissue that anchors the caudal end of the spinal cord to the coccyx. It begins as a pial extension from the conus medullaris, extends through the lumbar cistern surrounded by the cauda equina*, picks up a covering of dura mater at about vertebral level S2 (where the spinal dural sac ends), and merges with the periosteum of the coccyx.

Fourth ventricle.  The most caudal of the brain ventricles, shaped like a tent with a peaked roof protruding into the overlying cerebellum and a diamond-shaped floor formed by the dorsal surface of the pons and rostral medulla; continuous with the third ventricle via the cerebral aqueduct and open to the subarachnoid space through three foramina: one median aperture and two lateral apertures.

Fimbria.  Literally the “fringe,” a prominent band of white matter along the medial edge of the hippocampus*. The fimbria is an accumulation of myelinated axons (mostly efferent) that first collect on the ventricular surface of the hippocampus as the alveus. Near the splenium of the corpus callosum the fimbria separates from the hippocampus as the crus of the fornix*. Flocculus. The hemispheral component of the flocculonodular lobe, the part of the cerebellum* particularly concerned with the vestibular system and eye movements. Foramen of Monro. See interventricular foramen*.

P

Frontal lobe.  The most anterior lobe of each cerebral hemisphere. The frontal lobe includes motor, premotor, and supplementary motor cortex; an extensive prefrontal region; and a large expanse of orbital cortex. The latter two regions have access via long association fibers to all other lobes and also the limbic system; they are important (in ways still only partially understood) in working memory, decision making, and regulating emotional tone.

Su p

Fornix.  A prominent paired fiber bundle, mostly containing hippocampal efferents, that interconnects the hippocampus of each cerebral hemisphere and the ipsilateral septal nuclei and hypothalamus. Body.  Upper arched cable formed by the union of the crura beneath the septa pellucida in the midline. Column.  One of the two bundles that diverge from the body, then pass down and back toward the mammillary bodies. Crus.  One of the two origins (“legs”) of the body, formed by detachment of the fimbria from the hippocampus. Fimbria.  Hippocampal efferents that have assembled from the alveus on their way into the crus. Precommissural fornix.  Fornix fibers that leave the columns just above the anterior commissure, bound for the septal nuclei, ventral striatum, and some nearby cortical areas.

Septum pellucidum

e dl

In fe

M id

Interventricular foramen

ior er

rio

r

r e c e n t r a l

Body Column

Anterior commissure

Orbital Triangular Opercular Anterior paracentral lobule

Supe rior

Crus/body

Fimbria Alveus

Hippocampus

Fusiform gyrus. See occipitotemporal gyrus*. Globus pallidus.  A wedge-shaped nucleus medial to the putamen that gives rise to most of the efferents from the basal ganglia.

Glossary

GP e

External segment (GPe).  Afferents from the striatum, efferents (via the subthalamic fasciculus) to the subthalamic nucleus. Internal segment (GPi). Afferents from the striatum and subthalamic nucleus, efferents (via the ansa lenticularis and lenticular fasciculus) to the thalamus.

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Gracile tubercle.  A dorsomedial swelling on the caudal medulla, just caudal to the obex, overlying nucleus gracilis. Nucleus gracilis in turn gives rise to the part of the medial lemniscus that carries tactile and proprioceptive information from the leg and lower body.

GPi

Glomus.  An enlarged strand of choroid plexus in the atrium of the lateral ventricle. The glomus (“ball of thread”) accumulates calcium deposits with age and so can often be seen in CT images.

Great vein (great cerebral vein of Galen).  A large unpaired vessel arising in the superior cistern by union of the two internal cerebral veins. During its short course it receives the basal veins (of Rosenthal), then turns superiorly around the splenium of the corpus callosum and joins the inferior sagittal sinus to form the straight sinus. The great vein is a key conduit in the deep venous drainage of the brain. Internal cerebral vein

Gyrus rectus.  A slender straight convolution, medial to the orbital gyri* covering the rest of the inferior surface of the frontal lobe. Gyrus rectus has extensive limbic connections, particularly in circuits involving the amygdala. Provided by Dr. Raymond Carmody, University of Arizona

Glossopharyngeal nerve.  The 9th cranial nerve. Its rootlets emerge laterally from a shallow groove on the lateral surface of the medulla at the rostral end of the series of filaments that form the vagus nerve. The glossopharyngeal nerve contains afferents from taste buds, pharyngeal and middle ear mucous membranes, the carotid body and sinus, and skin of the outer ear; axons of motor neurons for a pharyngeal muscle (stylopharyngeus); and preganglionic parasympathetic axons for the parotid gland.

Habenula.  A small mound of neurons (derived from the embryonic diencephalon) on the dorsomedial surface of the posterior thalamus. The habenula receives diverse afferents from the ventral and medial forebrain (e.g., septal nuclei, preoptic area) that arrive through the stria medullaris of the thalamus. Habenular efferents descend to various paramedian midbrain reticular nuclei via the habenulointerpeduncular tract. Hence it is anatomically evident that the habenula is a relay in caudally directed limbic projections, although its exact role in primates is poorly understood.

IX X

XI Habenulointerpeduncular tract Provided by Dr. Norman Koelling, University of Arizona

XII

Habenulointerpeduncular tract.  Also called fasciculus retroflexus, owing to its lordotic curvature, conveys outputs from the stria

248

Glossary

medullaris/habenula* route precipitously down again to the paramedian midbrain reticular formation (where most other caudally directed limbic projections arrive more expediently by passing caudally through the hypothalamus).

Hypoglossal nucleus.  A group of motor neurons that innervate muscles of the ipsilateral half of the tongue. 

Heschl’s gyri. See transverse temporal gyri*. Hippocampus.  A specialized cortical area rolled into the medial temporal (or limbic) lobe. The hippocampus plays a critical role in the consolidation of new memories of facts and events. Anatomically, it has three subdivisions (until recently, usually referred to collectively as the hippocampal formation rather than the hippocampus), from within outward as follows: Dentate gyrus.  In cross section, one of two interlocking C-shaped strips of cortex (the hippocampus proper is the other). Afferents from entorhinal cortex, efferents to hippocampal pyramidal cells. Hippocampus proper (also called cornu ammonis, or Ammon’s horn).  Afferents from the dentate gyrus and septal nuclei, efferents to the subiculum and septal nuclei. Subiculum. A transitional zone between the hippocampus proper and entorhinal cortex, the subiculum receives afferents from the hippocampus proper and is the principal source of efferents from the hippocampus in general.

Hypoglossal trigone. A triangular elevation in the floor of the caudal fourth ventricle formed by the underlying hypoglossal nucleus. 

Fimbria

Ammon’s horn Alveus Dentate gyrus Subiculum

Hypoglossal nerve.  The 12th cranial nerve, whose rootlets emerge from the medulla in an anterolateral sulcus between the pyramid and the olive. It innervates intrinsic and extrinsic skeletal muscles of the tongue.

Hypothalamic sulcus.  A shallow, curved indentation (convex side down) in the wall of the third ventricle, extending from the interventricular foramen to the opening of the cerebral aqueduct. The hypothalamic sulcus is the boundary between the thalamus and the hypothalamus*.  Olive Pyramid

XII

Hypothalamus. The most inferior of the four divisions of the diencephalon, the hypothalamus plays a major role in orchestrating visceral and drive-related activities. It has three general zones: Anterior region.  Includes the suprachiasmatic, supraoptic, and paraventricular nuclei and continues anteriorly into the preoptic area; projects axons to the posterior lobe of the pituitary gland and to caudal sites (including the spinal cord). Tuberal region.  Includes the dorsomedial, ventromedial, and arcuate nuclei. The last secretes releasing hormones and inhibiting hormones into the pituitary portal system.

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Glossary Posterior region.  Includes the mammillary and posterior nuclei and projects to the thalamus and midbrain tegmentum. Preoptic area

Hypothalamic sulcus

Inferior parietal lobule.  The lower part of the lateral surface of the parietal lobe, below the intraparietal sulcus and behind the postcentral gyrus. The inferior parietal lobule consists of the angular and supramarginal gyri, which (in the dominant hemisphere) are functionally related to Wernicke’s area and thus important in the comprehension of language. Intraparietal sulcus

Angular gyrus Anterior

Tuberal

Posterior

Inferior brachium. See brachium of the inferior colliculus*. Inferior cerebellar peduncle.  A major input route to the cerebellum, containing crossed olivocerebellar fibers, the uncrossed posterior spinocerebellar and cuneocerebellar tracts, vestibulocerebellar fibers, and other cerebellar afferents. Sometimes referred to as the restiform (Latin for “ropelike”) body. Vestibular nuclei

Cochlear nuclei

Supramarginal gyrus

Inferior temporal gyrus.  The most inferior of three longitudinally oriented convolutions visible on the lateral aspect of the temporal lobe*. The inferior temporal gyrus is part of a large region of visual association cortex occupying most of the occipital lobe and much of the temporal lobe. Inferior thalamic peduncle. A small bundle of fibers emerging anteriorly from the thalamus and curving down toward the basal forebrain (just anterior to the ansa lenticularis). Its fibers include interconnections between the dorsomedial nucleus and orbital cortex, but they do not traverse the internal capsule like other thalamic connections. Mammillothalamic tract Stria medullaris

Ansa lenticularis + Lenticular fasciculus

Inferior olivary nucleus

Inferior colliculus.  A large, rounded mass of gray matter in the roof of the caudal midbrain. The inferior colliculus is a major link in the auditory system, receiving the lateral lemniscus and giving rise to the brachium of the inferior colliculus*, which in turn conveys auditory fibers to the thalamus (medial geniculate nucleus). Inferior frontal gyrus.  The most inferior of three longitudinally oriented gyri in the anterior part of the frontal lobe*. The opercular and triangular parts of this gyrus in the dominant hemisphere form Broca’s area, which is a language area important for the production of spoken and written language. Inferior olivary nucleus. A large nucleus in the anterolateral medulla, shaped like a bag, with a convoluted wall of gray matter (like a crumpled, pitted olive). Olivary afferents are diverse (from the spinal cord, red nucleus, deep cerebellar nuclei, etc.), but efferents are all olivocerebellar. They pour out of its medially facing mouth (or hilus), cross the midline as internal arcuate fibers, join the inferior cerebellar peduncle*, and blanket the contralateral cerebellum as climbing fibers that powerfully excite Purkinje cells and other neurons.

Inferior vestibular nucleus. See vestibular nuclei. Infundibulum.  The hollow, funnel-like stalk of the pituitary gland descending from the median eminence of the hypothalamus to the posterior lobe of the pituitary gland. The infundibulum arises during embryonic development as a ventral outgrowth of the floor of the diencephalon and is later joined by the anterior lobe derived from the roof of the oral cavity.

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Glossary

Insula.  The original lateral surface of the embryonic telencephalic vesicle overlying an area of fusion with the diencephalon, forming in the adult a central lobe of the cerebral hemisphere, typically convoluted into about three short gyri (located more anteriorly) and two long gyri. With rapid cerebral expansion during fetal development, the insula is overgrown and by birth concealed by frontal, parietal, and temporal opercula. It includes limbic, gustatory, and autonomic areas but is less well understood than other cortical areas because of its hidden location.

Intermediate gray. The spinal gray matter interposed between the posterior and anterior horns. It contains interneurons and tract cells of various sensory and motor circuits (including Clarke’s nucleus), preganglionic sympathetic neurons in thoracic and upper lumbar segments, and preganglionic parasympathetic neurons in segments S2-S4.

Anterior limb.  Between the lenticular nucleus and the head of the caudate nucleus. Connections between the thalamus (dorsomedial and anterior nuclei) and prefrontal and anterior cingulate cortex, plus many frontopontine fibers. Genu.  At the junction between the anterior and posterior limbs, adjacent to the anterior end of the thalamus. Connections between the thalamus (VA, VL) and motor/premotor cortex, plus some frontopontine fibers. Posterior limb.  Between the lenticular nucleus and the thalamus. Connections between the thalamus (VA, VL, VPL/VPM) and motor, somatosensory, and other parietal cortex, plus corticobulbar and corticospinal fibers. Retrolenticular part.  Passing posterior to the lenticular nucleus. Connections between the thalamus (pulvinar, LP) and parietaloccipital-temporal association cortex, plus the upper part of the optic radiation (from the lateral geniculate nucleus). Sublenticular part. Dipping under the posterior part of the lenticular nucleus. Projections to and from the temporal lobe, including the auditory radiation (from the medial geniculate nucleus) and the lower part of the optic radiation (from the lateral geniculate nucleus) before it turns posteriorly toward the occipital lobe.

Anterior limb Genu

Posterior limb

Preganglionic sympathetic neurons

Internal arcuate fibers.  A general term for the large collection of axons that arch across the midline of the medulla. Many internal arcuate fibers are axons leaving the posterior column nuclei to form the contralateral medial lemniscus, some are trigeminothalamic fibers leaving the spinal trigeminal nucleus to join the contralateral spinothalamic tract, and most others are efferents from the inferior olivary nucleus to the contralateral half of the cerebellum.

Sublenticular part Retrolenticular part

Internal carotid artery.  A large distributing artery, originating from the bifurcation of the common carotid artery and running cranially in the neck to enter the base of the skull and eventually the cranial vault. The internal carotid artery branches at the circle of Willis into anterior and middle cerebral arteries. The paired carotids account for about 80% of cerebral blood flow and thus supply most of the blood to the brain. Anterior cerebral arteries

Internal capsule. A compact, curved sheet of thalamocortical, corticothalamic, and other cortical projection fibers shaped like part of a funnel. The internal capsule is divided into five regions, based on each region’s relationship to the lenticular nucleus:

Middle cerebral arteries

Glossary Internal cerebral vein. The major deep vein of each cerebral hemisphere, formed at the interventricular foramen by the confluence of the smaller septal and terminal (thalamostriate) veins (the latter receiving the choroidal vein, which drains much of the choroid plexus). Immediately after its origin the internal cerebral vein bends sharply posteriorly (through the venous angle), proceeds posteriorly in the transverse fissure, and fuses with its counterpart in the superior cistern to form the unpaired great vein*.

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of the third ventricle but anatomically making the thalamus almost a single unpaired structure; see third ventricle*.) Interventricular foramen (of Monro).  The narrow orifice between each lateral ventricle and the third ventricle. Fornix

Internal medullary lamina (of the thalamus). A dense, curved sheet of myelinated fibers within the thalamus* that divides it into medial and lateral compartments everywhere except posteriorly, where it does not enter the pulvinar, and anteriorly, where it forks into a V-shaped groove for the anterior nuclei. The internal medullary lamina contains several small and two large intralaminar nuclei (the centromedian and parafascicular nuclei). Interpeduncular fossa.  A depression on the anterior aspect of the midbrain between the two cerebral peduncles. Its surface is pierced by penetrating branches of the basilar artery and is therefore termed the posterior perforated substance. Rootlets of the oculomotor nerve exit here. III

Cerebral peduncle

Anterior commissure

Intraparietal sulcus.  A longitudinally oriented sulcus on the lateral aspect of the parietal lobe, separating it into a superior parietal lobule above and an inferior parietal lobule* below. Lamina terminalis.  A thin membrane at the anterior end of the third ventricle, curving down from the rostrum of the corpus callosum to the optic chiasm and corresponding (roughly, if not precisely) to the rostral end of the neural tube. The lamina terminalis connects the two telencephalic vesicles of the embryonic forebrain and provides a route through which commissural fibers that will later make up the anterior commissure and corpus callosum begin to grow.

Interposed nucleus. The deep cerebellar nucleus interposed between the dentate and fastigial nuclei. The interposed nucleus has two distinct subdivisions, the globose nucleus medially and emboliform nucleus laterally (looks like an embolus in the hilus of the adjoining dentate nucleus). Both subdivisions receive input from the medial part of the ipsilateral cerebellar hemisphere; both project (via the superior cerebellar peduncle, like the dentate nucleus) to the red nucleus and the ventral lateral nucleus (VL) of the thalamus. (The projection of the interposed nucleus differs mainly in emphasis, favoring the red nucleus over VL, whereas the dentate projection is just the opposite.) Lateral aperture.  The aperture (also called the foramen of Luschka) at the end of each lateral recess of the fourth ventricle, through which this ventricle communicates with subarachnoid space.

Interthalamic adhesion (massa intermedia).  A small, ovoid area of continuity between the two thalami resulting from expansion and fusion of the walls of the third ventricle during development. The interthalamic adhesion is mainly gray matter, containing neurons and axonal and dendritic processes. (This structure is often reduced in size or absent, especially in the brains of older persons; however, in some mammals, such as rodents, it is massive, reducing the size

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Glossary

Lateral corticospinal tract.  The larger of the two corticospinal tracts, comprising those fibers (about 85%) in each medullary pyramid that enter the pyramidal decussation and cross the midline to the opposite lateral funiculus. The axons of this tract end on spinal motor neurons or (more often) on smaller interneurons that in turn synapse on motor neurons. Its fibers are often said to be arranged somatotopically, with those passing to more caudal cord levels located more laterally, but anatomical evidence does not support this view.

Lateral olfactory tract.  A small tract in humans (although relatively much larger in animals that rely more extensively on the sense of smell) through which fibers that originated in the olfactory bulb and passed through the olfactory tract continue on their way by traveling across the surface of the basal forebrain to olfactory cortex and the amygdala. C8

Piriform cortex

Lateral cuneate nucleus.  The equivalent for the arm of Clarke’s nucleus for the leg. Proprioceptive primary afferents travel through fasciculus cuneatus to this nucleus, which then gives rise to uncrossed cuneocerebellar fibers that enter the cerebellum via the inferior cerebellar peduncle. Lateral dorsal nucleus (LD). See thalamus*. Lateral funiculus.  One of the three major divisions of the spinal white matter, the others being the anterior and posterior* funiculi. The lateral funiculus contains various ascending and descending tracts, including the anterior and posterior spinocerebellar, spinothalamic, and lateral corticospinal tracts. Lateral geniculate nucleus (LGN). See thalamus*. Lateral horn.  A small, pointed lateral extension of the intermediate spinal gray from T1 through L2 or L3. The lateral horn contains the intermediolateral cell column, a long slender column of preganglionic sympathetic neurons supplying the entire body. Axons of these preganglionic sympathetic neurons leave through the ventral roots.

Preganglionic sympathetic neurons

Lateral lemniscus.  A flattened ribbon of fibers on the lateral surface of the rostral pontine tegmentum, arising from the cochlear and superior olivary nuclei. The lateral lemniscus is part of the ascending auditory pathway, conveying information from both ears to the inferior colliculus.

Periamygdaloid cortex

Lateral posterior nucleus (LP). See thalamus*. Lateral sulcus (Sylvian fissure).  A long, deep indentation on the lateral aspect of each cerebral hemisphere resulting from downward and forward expansion of the temporal lobe during fetal development. The insula lies hidden within the depths of this sulcus, which separates the temporal lobe from the frontal and parietal lobes and provides a route by which the middle cerebral artery accesses the lateral convexity.

Lateral ventricle.  The large central cavity of each cerebral hemisphere, following a C-shaped course through the hemisphere and derived from the lumen of the embryonic telencephalic vesicle. Anterior horn.  The frontal horn, in the frontal lobe anterior to the interventricular foramen. Body.  In the frontal and parietal lobes, extending posteriorly to the region of the splenium of the corpus callosum. Atrium (or trigone). The region near the splenium of the corpus callosum where the body and the posterior and inferior horns meet.

Glossary Inferior horn.  The temporal horn, curving down and forward into the temporal lobe. Posterior horn.  The occipital horn, projecting backward into the occipital lobe. Body

Anterior horn

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Lenticulostriate arteries. A collection of about a dozen small branches of the middle cerebral artery along its course toward the lateral sulcus. They penetrate the overlying brain near their origin and pass upward to supply deep structures (internal capsule, globus pallidus, putamen). The lenticulostriate arteries exemplify a large collection of small penetrating arteries that arise from all arteries around the base of the brain; these narrow, thin-walled vessels are involved frequently in strokes that deprive deep cerebral structures of blood and thus cause neurological deficits out of proportion to their size.

Posterior horn

Inferior horn

Provided by Dr. John Sundsten, University of Washington

Lateral vestibular nucleus. See vestibular nuclei. Lenticular fasciculus.  Part of the projection from the globus pallidus to the thalamus. It has more axons than the other part (see ansa lenticularis) and is more spread out, forming numerous conspicuous bundles of myelinated fibers running medially through the internal capsule, like the teeth of a comb. Medial to the internal capsule, the lenticular fasciculus is joined by the ansa lenticularis before both enter the thalamus through the thalamic fasciculus.

Limbic lobe.  The most medial lobe of the cerebral hemisphere, facing the midline and visible grossly only in sagittal sections. The limbic lobe consists of a continuous border zone of cortex around the corpus callosum, comprising the cingulate and parahippocampal gyri and their narrow connecting isthmus; this lobe and its many connections, cortical and subcortical, make up a large part of the limbic system and give the latter its name. Cingulate gyrus

Lenticular nucleus. The putamen and globus pallidus considered as one anatomical structure.

Isthmus

Parahippocampal gyrus

Limen insulae.  Limen is Latin for “threshold” and in this case refers to the transition point from anterior perforated substance to insula. The circular sulcus, which surrounds almost the entire insula, ends on either side of the limen insulae, allowing access for the middle cerebral artery.

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Lingual gyrus.  The gyrus forming the inferior bank of the calcarine sulcus. The lingual gyrus overlaps the posterior part of the occipitotemporal gyrus, separated from it by the collateral sulcus.

Papez circuit—a grand loop from hippocampus through hypothalamus, thalamus, and cortex back to hippocampus again—was unquestionably the impetus for the decades of research that led to the limbic system concept of today. Fornix

Mammillothalamic tract

Lissauer’s tract.  A pale-staining area of white matter between the substantia gelatinosa* (capping the posterior horn of the spinal gray matter) and the pial surface of the cord. Lissauer’s tract stains more lightly than the rest of the spinal white matter because it contains finely myelinated and unmyelinated pain and temperature fibers (derived from the lateral division of each dorsal root filament) that then distribute into the underlying substantia gelatinosa over several segments. Locus ceruleus.  A column of pigmented, blue-black neurons (locus ceruleus is Latin for “blue place”) near the floor of the fourth ventricle, extending through the rostral pons. Locus ceruleus neurons provide most of the far-flung noradrenergic innervation of the forebrain.

Provided by Dr. Norman Koelling, University of Arizona

Mammillothalamic tract.  The projection from the mammillary body* to the anterior nucleus of the thalamus; part of the Papez circuit. Medial geniculate nucleus (MGN). See thalamus*. Medial forebrain bundle.  A collection of thinly myelinated and unmyelinated fibers running longitudinally through the lateral hypothalamus and reaching the basal forebrain and the brainstem tegmentum. It interconnects the hypothalamus with both these areas and also conveys monoaminergic fibers on their way from the brainstem to widespread forebrain areas. Medial lemniscus.  Somatosensory afferents originating from the contralateral posterior column nuclei and trigeminal main sensory nucleus and ascending through the brainstem to the thalamus (VPL/ VPM). The medial lemniscus is the principal ascending pathway for tactile and proprioceptive information.

Longitudinal fissure.  An extensive vertical cleft, oriented sagittally and occupied by the falx cerebri, separating the two cerebral hemispheres around the margin of the undivided corpus callosum.

Medial longitudinal fasciculus (MLF).  A longitudinal fiber bundle involved in coordinating eye and head movements. Each MLF

Mammillary body. A prominent component of the posterior hypothalamus. The mammillary body receives afferents from the hippocampus (chiefly the subiculum) via the fornix and sends efferents to the anterior nucleus of the thalamus via the mammillothalamic tract. This is part of a historic neural circuit proposed by James Papez in 1937 as an anatomical substrate for emotion. Although derided by some then and viewed as simplistic by others now, the

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Glossary includes fibers from contralateral abducens interneurons to medial rectus motor neurons in the oculomotor nucleus. It is also the route of descent for fibers of the medial vestibulospinal tract. Medial striate artery.  A large penetrating branch of the anterior cerebral artery, also known as the recurrent artery of Heubner. It supplies the striatum and internal capsule in the region of nucleus accumbens and some posterior parts of orbital cortex. Medial vestibular nucleus. See vestibular nuclei. Median aperture.  One of the three apertures through which the fourth ventricle communicates with subarachnoid space. The median aperture (also called the foramen of Magendie) opens into cisterna magna.

and caudally with the spinal cord. This small structure is important out of proportion to its size: it is crucial to vital functions (respiratory, cardiovascular, visceral activity) and other integrative activities. In addition, most sensory and motor tracts of the CNS run up and down through it. Midbrain (mesencephalon).  The most rostral of the three subdivisions of the brainstem. The midbrain remains tubular in plan but features a great variety of structures: the superior and inferior colliculi in its roof (tectum), aqueduct and periaqueductal gray, oculomotor and trochlear nuclei and pretectal area, upper part of the reticular formation, red nuclei, substantia nigra, and cerebral peduncles. Like the medulla, a small region of enormous importance.

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Median eminence.  A swelling at the base of the hypothalamus, in the middle of the tuber cinereum, from which the infundibulum arises. The median eminence lacks a blood-brain barrier and is the site at which hypothalamic releasing hormones and inhibiting hormones gain access to the portal system that delivers them to the anterior pituitary.

Middle cerebellar peduncle.  The largest of the cerebellar peduncles, containing fibers that arise in the basal pons* from contralateral pontine nuclei and end as mossy fibers in almost all areas of cerebellar cortex. Sometimes referred to as the brachium pontis (the “arm of the pons”). Middle cerebral artery.  The more posterior of the two terminal branches of the internal carotid artery*. The middle cerebral artery runs laterally beneath the basal forebrain to reach the lateral sulcus, where many branches arise. It supplies the insula, most of the lateral surface of the cerebral hemisphere, and the anterior tip of the temporal lobe. Middle frontal gyrus.  One of three longitudinally oriented gyri in the anterior part of the frontal lobe*, situated between the superior and inferior frontal gyri. It includes part of premotor cortex, as well as the frontal eye field, which is involved in initiating voluntary eye movements to the contralateral side.

Medulla (medulla oblongata). The most caudal of the three subdivisions of the brainstem, continuous rostrally with the pons

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Middle temporal gyrus.  One of three longitudinally oriented gyri on the lateral surface of the temporal lobe* between the superior and inferior temporal gyri. It contains some visual association cortex, as well as multimodal or heteromodal association cortex. MLF. See medial longitudinal fasciculus*.

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Nucleus accumbens.  The most inferior part of the striatum*, with predominantly limbic connections. Nucleus accumbens was traditionally known as nucleus accumbens septi but is now recognized as a major component of the ventral striatum. (The original, longer name reflects its position immediately lateral to the base of the septum pellucidum, as if leaning against it.)

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Nucleus ambiguus.  A collection of motor neurons for laryngeal and pharyngeal muscles, and preganglionic parasympathetic neurons for the heart. So called because these neurons are somewhat scattered in the reticular formation of the rostral medulla and do not form a compact, easily seen nucleus.

Occipital lobe.  The most posterior lobe of each cerebral hemisphere. The occipital lobe includes the primary visual cortex in the banks of the calcarine sulcus, as well as adjoining areas of visual association cortex.

Cuneus

Lingual gyrus

Nucleus cuneatus.  The more lateral of the posterior column nuclei*. Site of termination of fasciculus cuneatus and origin of the arm region of the medial lemniscus. Nucleus gracilis.  The more medial of the posterior column nuclei*. Site of termination of fasciculus gracilis and origin of the leg region of the medial lemniscus.

Occipitotemporal gyrus (fusiform gyrus).  A long gyrus, beginning just lateral to the uncus and running posteriorly along the inferior surface of the temporal lobe into the occipital lobe. Along its course in the temporal lobe, the occipitotemporal gyrus is bounded laterally by the inferior temporal gyrus and medially by the parahippocampal gyrus.

Nucleus of the solitary tract.  The principal visceral sensory nucleus of the brainstem; the site of termination of the visceral and gustatory primary afferents in the solitary tract, which it surrounds, doughnutlike, in cross section.

Solitary tract

Oculomotor nerve. The 3rd cranial nerve, emerging into the interpeduncular fossa of the midbrain. The oculomotor nerve innervates most of the extrinsic ocular muscles (see also oculomotor nucleus): superior, medial, and inferior recti, inferior oblique, and levator palpebrae superioris. It also conveys preganglionic parasympathetic fibers to the ciliary ganglion, where postganglionic fibers arise to innervate the pupillary sphincter and ciliary muscle.

Obex. Apex of the V-shaped caudal fourth ventricle, where the ventricle narrows into the central canal of the caudal medulla and the spinal cord.

Oculomotor nucleus. Motor neurons for the ipsilateral medial and inferior recti and inferior oblique, the contralateral superior rectus, and the levator palpebrae of both sides. Preganglionic parasympathetic neurons in one of its columns, the Edinger-Westphal nucleus*, control the ipsilateral pupillary sphincter and ciliary muscle.

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Opercula (singular, operculum).  The parts of the frontal, parietal, and temporal lobes bordering the lateral sulcus and overlying the insula, hiding it from view.

Oculomotor nerves

Olfactory bulb.  The knoblike anterior end of the olfactory tract* on the orbital surface of the frontal lobe. The olfactory bulb is the site of central termination of incoming olfactory fibers (cranial nerve I) from the olfactory epithelium in the nasal cavity. It is large and well laminated in animals that depend heavily on the sense of smell (e.g., rats, dogs), but relatively small and poorly differentiated in the human brain. Olfactory sulcus.  A sulcus on the orbital surface of the frontal lobe, immediately lateral to gyrus rectus and harboring the olfactory bulb and tract*.

Opercular part (of the inferior frontal gyrus).  The most caudal part of the inferior frontal gyrus, the most inferior of three longitudinally oriented gyri in the anterior part of the frontal lobe*. In the dominant hemisphere, it forms the posterior half of Broca’s area.

Olfactory tract.  Projections from olfactory bulb neurons (mitral and tufted cells) to olfactory (piriform) cortex and the amygdala. The olfactory tract also conveys modulatory efferents traveling from deeper CNS centers back to the olfactory bulb.

Optic chiasm.  The site at which optic nerve fibers from ganglion cells in the nasal half of each retina decussate, so that each optic tract contains fibers arising in the temporal retina of the ipsilateral eye and the nasal retina of the opposite eye.

Olfactory: sulcus bulb tract

Optic: nerve chiasm tract

Infundibulum Mammillary body CN III Provided by Dr. Norman Koelling, University of Arizona

Optic nerve.  The 2nd cranial nerve, containing axons of the various types of retinal ganglion cells projecting to the lateral geniculate nucleus of the thalamus, the superior colliculus, pretectal area, suprachiasmatic nucleus of the hypothalamus, and a few other sites. Olfactory tubercle. A restricted area of the anterior perforated substance where some olfactory tract fibers terminate. The olfactory tubercle forms a distinct elevation in some animals but is not very apparent in human brains. Olive.  Protuberance on the lateral aspect of the rostral medulla, just dorsolateral to the pyramid, caused by the underlying inferior olivary nucleus.

Provided by Dr. Norman Koelling, University of Arizona

Optic radiation. A conspicuous, sharply defined, and heavily myelinated bundle of visual fibers originating in the lateral geniculate nucleus of the thalamus, departing through the retrolenticular and sublenticular parts of the internal capsule, curving in a broad fan around the atrium and the posterior and inferior horns of the lateral ventricle, and terminating in the primary visual cortex in the upper and lower banks of the calcarine sulcus.

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Optic tract.  Axons of ganglion cells from corresponding (homonymous) halves of each retina on their way to the lateral geniculate nucleus of the thalamus, superior colliculus, pretectal area, and a few other sites.

Paraterminal gyrus.  A small patch of cortex adjacent to the lamina terminalis, continuous with the subcallosal gyrus* and through it with the rest of the limbic lobe.

Orbital gyri.  The variably sulcated (in a pattern often resembling the letter H) group of gyri that make up most of the orbital surface of the frontal lobe. The orbital gyri usually are not named individually, in contrast to the gyrus rectus immediately medial to them. (Gyrus rectus is on the orbital surface but is usually not included among the orbital gyri.)

Parietal lobe. A cerebral lobe bounded by the frontal, temporal, and occipital lobes on the lateral surface of each hemisphere, and by the frontal, limbic, and occipital lobes on the medial surface. The parietal lobe contains primary somatosensory cortex in the postcentral gyrus, areas involved in language comprehension (in the inferior parietal lobule, usually on the left), and regions involved in complex aspects of spatial orientation and perception.

Gyrus rectus

Orbital gyri

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Parabrachial nuclei.  A collection of nuclei adjacent to the superior cerebellar peduncle (brachium conjunctivum) as the latter traverses the rostral pons. Various parts of the parabrachial nuclei are involved in transferring visceral, pain, and temperature information to the hypothalamus and amygdala.

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Orbital part (of the inferior frontal gyrus). The most anterior part of the inferior frontal gyrus, the most inferior of three longitudinally oriented gyri in the anterior part of the frontal lobe*, so named because it merges with the orbital gyri.

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Intraparietal sulcus

Posterior paracentral lobule Parietooccipital sulcus Precuneus

Parietooccipital sulcus.  A deep fissure separating the parietal* and occipital lobes on the medial aspect of the cerebral hemisphere. Inferiorly, the parietooccipital sulcus joins the calcarine sulcus*, which continues into the temporal lobe as a common stem for both these sulci. Paracentral lobule.  The extensions of the precentral and postcentral gyri onto the medial surface of the hemisphere, forming a lobule that surrounds the end of the central sulcus. Top of central sulcus

Periamygdaloid cortex.  A cortical area covering part of the amygdala and merging with it; part of primary olfactory cortex. (See lateral olfactory tract*.) Periaqueductal gray.  An area of gray matter and poorly myelinated fibers surrounding the aqueduct in the midbrain. The periaqueductal

Parafascicular nucleus (PF). See thalamus*. Parahippocampal gyrus.  The gyrus immediately adjacent to (and continuous with) the hippocampus, forming a major part of the limbic lobe*. Its anterior region contains the entorhinal cortex, a meeting ground for cortical projections from multiple areas and the source of most afferents to the hippocampus.

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Glossary gray is the site of origin of a descending pain-control pathway that relays in nucleus raphe magnus (among other connections). Periventricular gray.  The continuation of the periaqueductal gray into the floor of the fourth ventricle.

It secretes a variety of hormones that control other endocrine glands at rates dictated by releasing hormones and inhibiting hormones that reach it from the median eminence via the pituitary portal system. Pons.  The second of the three parts of the brainstem, continuous rostrally with the midbrain and caudally with the medulla. The pons is overlain by the cerebellum and includes an enlarged basal region (see basal pons).

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Pineal gland.  A dorsal outgrowth of the diencephalon, protruding from the third ventricle immediately caudal to the paired habenulae. The pineal is an endocrine gland important in seasonal cycles of some animals. In humans it secretes the hormone melatonin, which is involved in the synchronization of circadian rhythms.

Pontine nuclei.  A collective term for the many small nuclei in the basal pons* that receive afferents from the cerebral cortex (via the internal capsule and cerebral peduncle) and project to the contralateral cerebellar cortex (via the middle cerebellar peduncle). Pontocerebellar fibers.  Projections from pontine nuclei that cross in the basal pons*, traverse the middle cerebellar peduncle, and enter the contralateral cerebellar cortex, where they terminate as mossy fibers (as do all cerebellar afferents except those from the inferior olivary nucleus).

Piriform cortex.  A cortical area adjacent to the lateral olfactory tract* as it moves toward the temporal lobe; part of primary olfactory cortex. Pituitary gland.  The two-part gland through which the hypothalamus controls most other endocrine glands. The posterior lobe of the pituitary is an outgrowth of the diencephalon and remains connected to the median eminence through the infundibulum. Neurons of the hypothalamic supraoptic and paraventricular nuclei release oxytocin and vasopressin into the bloodstream in the posterior lobe. The anterior lobe, although attached to the posterior lobe and infundibulum, is derived embryologically from the roof of the oral cavity.

Postcentral gyrus.  A vertically oriented convolution of the parietal lobe* immediately posterior to the central sulcus. The postcentral gyrus is the site of the primary somatosensory cortex. Posterior cerebral artery.  A prominent artery that arises from the bifurcation of the basilar artery at the level of the midbrain. The posterior cerebral artery forms the caudal part of the circle of Willis and supplies the rostral midbrain, much of the thalamus, the medial occipital lobe, and inferior and medial surfaces of the temporal lobe.

Superior cerebellar a. Basilar AICA PICA Vertebral a.

Provided by Dr. Elena Plante, University of Arizona

Posterior column.  The entire contents of one posterior funiculus except for its share of the propriospinal tract (a thin shell of white matter around the gray matter).

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Posterior column nuclei.  Nuclei gracilis and cuneatus, the principal collections of second-order neurons receiving touch and position information from the body. Site of termination of fasciculi gracilis and cuneatus and origin of the contralateral medial lemniscus.

lemniscus system, the major pathway to cerebral cortex for lowthreshold cutaneous, joint, and muscle receptor information.

Posterior funiculus Nucleus gracilis Nucleus cuneatus

Fasciculus cuneatus

Posterior commissure. Crossing fibers interconnecting the two sides of the rostral midbrain and pretectal area. These crossing fibers are involved in the consensual pupillary light reflex and in coordinating vertical eye movements. Pretectal area

Pulvinar

Anterior funiculus

Lateral funiculus

Posterior horn.  One of the three general divisions of the spinal gray matter, the others being the anterior horn and the intermediate gray; contains second-order sensory neurons of multiple types and is capped at all levels by the substantia gelatinosa.

Substantia gelatinosa

Posterior communicating artery. A short vessel connecting the posterior cerebral artery to the internal carotid, thereby forming one link in the circle of Willis. These arteries are often asymmetrical, with one being considerably larger than the other. Normally pressures in the internal carotid and posterior cerebral arteries are balanced so that little or no blood flows around the circle, but if one vessel is occluded, the posterior communicating artery may allow anastomotic flow and thus prevent neurologic damage.

Posterior inferior cerebellar artery.  A long, circumferential branch of the vertebral artery, arising before the two vertebrals fuse to form the basilar artery. It supplies much of the inferior surface of the cerebellar hemisphere and vermis, en route sending shorter branches to the choroid plexus of the fourth ventricle and to much of the lateral medulla; commonly referred to by the acronym PICA.

Posterior cerebral a. Superior cerebellar a. Basilar AICA

Posterior funiculus.  One of the three major divisions of the spinal white matter, the others being the anterior and lateral funiculi. Principally occupied by ascending collaterals of large myelinated primary afferents carrying impulses from various kinds of mechanoreceptors. This is the first stage of the posterior column–medial

Vertebral a.

Posterior root. See dorsal root.

Glossary Posterior spinocerebellar tract. Uncrossed fibers from Clarke’s nucleus, carrying proprioceptive information from the arm to the ipsilateral half of the cerebellar vermis and medial hemisphere via the inferior cerebellar peduncle.

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to premotor and supplementary motor areas. The putamen forms the outer component of the lenticular nucleus (the globus pallidus is the inner part). Pyramid.  Corticospinal fibers from the ipsilateral precentral gyrus and adjacent areas of cerebral cortex, forming a prominent fiber bundle (roughly triangular in cross section, which gave rise to the name) on the ventral surface of the medulla.

Precentral gyrus.  A vertically oriented convolution of the frontal lobe* immediately anterior to the central sulcus. The precentral gyrus is the site of primary motor cortex. Precuneus.  The part of the parietal lobe* on the medial surface of the hemisphere, excluding the posterior paracentral lobule (the medial extension of the postcentral gyrus).

Pyramidal decussation.  The site, located at the spinomedullary junction, at which most fibers in each pyramid cross the midline to form the contralateral lateral corticospinal tract.

Preoccipital notch.  The midpoint of a shallow, curved indentation along the inferior margin of the lateral aspect of each cerebral hemisphere. The preoccipital notch serves as a landmark for synthesizing boundaries for the parietal, occipital, and temporal lobes on the lateral and medial surfaces of hemisphere.

Raphe nuclei.  A series of nuclei extending through the brainstem near the midline of the tegmentum, collectively providing the serotonergic innervation of the CNS. Red nucleus.  The site of termination of part of the superior cerebellar peduncle, and the site of origin of uncrossed fibers to the inferior olivary nucleus and of the crossed rubrospinal tract.

Preoptic area.  The area in the walls of the third ventricle immediately anterior to the optic chiasm, continuing into the lamina terminalis; once considered a telencephalic region, but structurally and functionally continuous with the hypothalamus* of the diencephalon. Pretectal area. The region between the superior colliculus and posterior thalamus. The pretectal area receives afferents from the retina and visual association cortex. It projects efferents bilaterally to the Edinger-Westphal nuclei, crossing both in the posterior commissure* and in the ventral periaqueductal gray. It is important in the pupillary light reflex. Pulvinar. See thalamus*. Putamen.  The part of the striatum* involved most prominently in the motor functions of the basal ganglia. The putamen receives afferents from cerebral cortex (primarily motor and somatosensory areas) and from the substantia nigra (compact part) and the centromedian nucleus of the thalamus. It projects efferents to the globus pallidus, which in turn projects via the thalamus (VA, VL)

Cerebellothalamic fibers

Reticular formation.  The central region of the brainstem, forming most of the tegmentum of the midbrain, pons, and medulla, with a complex netlike fabric of nerve cell bodies and interwoven processes; its myriad multimodal afferents, profusely collateralizing efferents running upward and downward to every level of the CNS, and involvement in virtually every activity from visceral functions to consciousness, make it a core integrating structure of the brain. Reticular nucleus. See thalamus*.

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Rhinal sulcus.  A sulcus demarcating the lateral boundary of the uncus on the medial aspect of the temporal lobe; sometimes continuous with the collateral sulcus behind it.

Spinal cord.  The most caudal subdivision of the CNS, extending from the pyramidal decussation to the conus medullaris at about vertebral level L1-L2. The human spinal cord has 31 segments and 2 enlargements (cervical, C5-T1, and lumbar, L2-S3). Spinothalamic tract.  Crossed fibers from neurons in the posterior horn of the spinal cord conveying pain and temperature information to the thalamus (VPL and other nuclei). Straight sinus.  A venous channel in the line of attachment between the falx cerebri and tentorium cerebelli. The straight sinus collects blood from the deep cerebral veins, which reaches it primarily by way of the great vein. The straight and superior sagittal sinuses* then meet at the confluence of the sinuses and empty into the transverse sinuses.

Septal nuclei.  A component of the medial wall of each cerebral hemisphere just beneath the base of the largely glial septum pellucidum. The septal nuclei are continuous inferiorly with the preoptic area of the hypothalamus and are reciprocally connected with the hippocampus, amygdala, hypothalamus, and other limbic structures via the fornix, stria terminalis, and other tracts. They are also the source of cholinergic input to the hippocampus. Septum pellucidum

Stria medullaris (of the thalamus).  The site of attachment of the roof of the third ventricle and a route through which efferents from the septal nuclei reach the habenula.

Septal vein

Septal vein.  A deep cerebral vein that runs posteriorly across the septum pellucidum to join the terminal (thalamostriate) vein and form the internal cerebral vein. Septum pellucidum.  A thin, chiefly glial, almost transparent, paired membrane separating the two lateral ventricles, grading inferiorly into the septal nuclei*. (In most brains the two septa pellucida are so closely apposed as to appear as a single structure, and for simplicity they are so labeled in most of the illustrations in this book.) Solitary tract.  Primary afferents conveying visceral and gustatory information from cranial nerves VII, IX, and X to the adjacent nucleus of the solitary tract*, which surrounds it.

Stria terminalis.  A slender, poorly myelinated tract following a long C-shaped course within the thalamostriate groove that separates the caudate nucleus from the thalamus. The stria terminalis plays a role analogous to that played by the fornix for the hippocampus: it conveys efferents from the amygdala to the septal nuclei and hypothalamus.

Glossary Striatum. An inclusive term for the caudate nucleus, putamen, and nucleus accumbens.

Caudate nucleus

Putamen Nucleus accumbens

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difficult to justify anatomically. (The frequently mentioned strumulotrivionimboeffluviostrumular loop apparently does not exist.) The clinical importance of the strumus is based on the disorder subacute combined strumuloma. This is an idiopathic disease of exquisitely rare occurrence and indeterminate symptomatology that forms the basis for the identification of the strumus as the center controlling involuntary higher cortical functions. Subcallosal fasciculus. A compact group of lightly staining myelinated fibers in the white matter of each cerebral hemisphere (visible mainly in the frontal lobe). The subcallosal fasciculus forms a pale, arched band adjacent to the corpus callosum and caudate nucleus and contains afferents on their way from the cerebral cortex (mainly association areas) to the caudate nucleus. Nearby association fibers that interconnect the frontal lobe and the occipital, parietal, and temporal lobes are sometimes considered separately as the superior occipitofrontal fasciculus.

Stripe of Gennari.  A sheet of myelinated fibers that run through one of the middle layers of primary visual cortex, giving it the distinctive appearance that gave rise to its alternate name, striate cortex. Named for the medical student who first described it in the 18th century.

Subcallosal gyrus.  The continuation of the cingulate gyrus under the rostrum of the corpus callosum, in turn continuing into the paraterminal gyrus. Paraterminal gyrus

Strumus (commonly misspelled “strumous”).  A primitive telencephalic extension that, unlike structures such as the neocortex that have expanded greatly in primates, has remained constant in size and position. It is located rostral to the lamina terminalis, medial to gyrus rectus, and ventromedial to the substantia innominata. Only the anterior and ventral nuclear groups are developed in humans, and these are subdivided cytoarchitectonically into four discrete nuclei: the anteroventral, the anterior ventral, and the subdivided anterior and ventral anterior nuclei. The interconnections of the strumus are extensive and complex, but their importance cannot be underestimated. There are four major afferent pathways: a substantial input from a variably present limbic nucleus, the effluvium, traveling through the superior and inferior effluviostrumular tracts; and minor inputs from the trivium and nimbus in the temporal lobe. Because the strumus has no known efferent pathways, however, its functional importance has been

Subiculum. See hippocampus*.

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Glossary

Subparietal sulcus. A variable sulcus on the medial surface of the hemisphere, separating the precuneus from the posterior part of the cingulate gyrus. The subparietal sulcus is roughly in line with the cingulate sulcus, and in about a third of hemispheres the two are continuous with each other (see Fig. 1.8A).

Subthalamic fasciculus. Small bundles of fibers that cross the internal capsule like the teeth of a comb. Fibers of the subthalamic fasciculus interconnect the globus pallidus and subthalamic nucleus*, which face each other on either side of the internal capsule. Subthalamic nucleus.  A lens-shaped, biconvex mass of gray matter just medial and superior to the junction of the internal capsule and cerebral peduncle. The subthalamic nucleus is a major link in an indirect route through the basal ganglia: striatum → globus pallidus (external segment) → subthalamic nucleus → globus pallidus (internal segment) → thalamus. The globus pallidus–subthalamic nucleus connections travel in the subthalamic fasciculus.

Caudate

Putamen

Substantia gelatinosa.  A distinctive region of gray matter, adjacent to Lissauer’s tract, that caps the posterior horn of the spinal cord at all levels. The substantia gelatinosa looks pale in myelin-stained material because its inputs are poorly myelinated or unmyelinated. It deals mostly with pain and temperature sensation.

GPe GPi

Lissauer’s tract

Subthalamic fasciculus

Substantia innominata.  Literally “the stuff with no name,” a now seldom-used term roughly synonymous with basal forebrain, left over from an era when the components of the basal forebrain were less well understood.

Sulcus limitans.  A longitudinal groove in the embryonic neural tube that separates sensory nuclei from motor nuclei. In the adult brain it persists as a groove in the floor of the fourth ventricle that separates motor nuclei of cranial nerves (medial to it) from sensory nuclei of cranial nerves.

Substantia nigra. A large, flattened nucleus in the midbrain, interposed between the red nucleus and cerebral peduncle. The substantia nigra has two parts: a compact part, containing closely packed, pigmented (with neuromelanin) dopaminergic neurons that project to the striatum, and a reticular part, containing more loosely arranged neurons, receiving inputs from the striatum and projecting to the thalamus. Compact part

Superior brachium. See brachium of the superior colliculus*. Superior cerebellar artery.  A branch of the basilar artery* that arises just caudal to the bifurcation of the basilar artery into the posterior cerebral arteries. Long circumferential branches supply the superior surface of the cerebellum, and shorter branches supply much of the rostral pons and caudal midbrain.

Reticular part

Ventral tegmental area

265

Glossary Superior cerebellar peduncle.  The major efferent route from the cerebellum, containing projections from deep cerebellar nuclei on their way to the red nucleus and the thalamus (mainly VL). Sometimes referred to as the brachium conjunctivum (a “conjoined arm,” named for its course through a decussation with its contralateral counterpart).

Superior olivary nucleus. A complex of nuclei near the rostral end of the facial nucleus in the caudal pons. The superior olivary nucleus is the first site of convergence of fibers representing the two ears and is the source of many fibers of the lateral lemniscus. It is also the origin of olivocochlear fibers that travel centrifugally in the vestibulocochlear nerve and terminate in the organ of Corti, modulating hair cell activity. Internal genu (facial nerve)

MLF

Facial nucleus

Decussation

Medial lemniscus

Superior cistern.  The enlarged, CSF-filled subarachnoid cistern above the midbrain, also termed the quadrigeminal cistern and the cistern of the great cerebral vein. The superior cistern is an important radiological landmark, continuous anteriorly and posteriorly with the transverse fissure and laterally with thin, curved spaces that partially encircle the midbrain before joining its underlying interpeduncular cistern (see interpeduncular fossa). (The combination of the superior cistern and these sheetlike extensions is known as the ambient cistern.)

Superior parietal lobule.  The upper part of the lateral surface of the parietal lobe*, above the intraparietal sulcus. The superior parietal lobule contains somatosensory association cortex. Superior sagittal sinus.  A venous channel in the superior line of attachment of the falx cerebri, providing the major outflow pathway for superficial cerebral veins.

Straight sinus Provided by Dr. Elena Plante, University of Arizona

Provided by Dr. Elena Plante, University of Arizona

Superior colliculus.  A large, rounded mass of gray matter in the roof of the rostral midbrain. The superior colliculus receives afferents from the retina and visual cortex (via the brachium of the superior colliculus*), sends efferents to the pulvinar of the thalamus and other structures, and plays a role in visual attention and control of eye movements. Superior frontal gyrus.  The most superior of three longitudinally oriented gyri in the anterior part of the frontal lobe*, continuing on to the medial surface of the hemisphere. The superior frontal gyrus includes supplementary motor cortex and part of premotor cortex.

Superior temporal gyrus.  The uppermost gyrus of the temporal lobe*, bordering on the lateral sulcus. The superior temporal gyrus includes primary auditory cortex (actually located in the wall of the lateral sulcus, in transverse temporal gyri crossing the top of the superior temporal gyrus), auditory association cortex, and (usually on the left) Wernicke’s area. This is one example of a region of visibly different size and configuration in the two cerebral hemispheres, typically being more extensive in the left hemisphere. Superior vestibular nucleus. See vestibular nuclei. Supramarginal gyrus.  The part of the inferior parietal lobule* surrounding the upturned end of the lateral sulcus. Although variable in size and shape, the supramarginal gyrus (usually on the left) is important in language function.

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Glossary

Tegmentum.  A general anatomical term for the area anterior to the ventricular spaces of the medulla, pons, and midbrain. Tegmentum (Latin for “covering”) is a useful umbrella term for all structures covering the basal components of the brainstem (pyramids, basal pons, cerebral peduncles) and includes the reticular formation, nuclei of cranial nerves, most ascending and descending tracts, the red nuclei, and substantia nigra.

lenticular fasciculus), gathered together beneath the ventral anterior and ventral lateral nuclei (VA/VL) of the thalamus. Thalamic fasciculus

Temporal lobe.  The most inferior lobe of each cerebral hemisphere, inferior to the lateral sulcus and anterior to the occipital lobe. The temporal lobe includes primary auditory and auditory association cortex, part of posterior language cortex, visual and higher-order association cortex, primary and association olfactory cortex, the amygdala, and the hippocampus. (The parahippocampal gyrus, a major part of the limbic lobe, is also commonly referred to as part of the medial temporal lobe.)

Thalamostriate vein. See terminal vein*.

Superior

Middle Inferior

Collateral sulcus

Rhinal sulcus

pitotem Occi po

Inferior

ral

Terminal vein. A deep cerebral vein that travels with the stria terminalis in the groove between the thalamus and adjacent caudate nucleus and drains much of these two structures. (Because of the location of this groove, the terminal vein is also referred to as the thalamostriate vein.)

Thalamic fasciculus.  Projections from the cerebellum (via the superior cerebellar peduncle) and basal ganglia (via the ansa lenticularis and

Thalamus.  A collection of nuclei that collectively are the source of most extrinsic afferents to the cerebral cortex. Some thalamic nuclei (relay nuclei) receive distinct input bundles and project to discrete functional areas of the cerebral cortex. Others (association nuclei) are primarily interconnected with association cortex. Still others have diffuse cortical projections, and one (the reticular nucleus) has no projections to the cortex at all. Anterior nucleus.  The thalamic relay nucleus for part of the limbic lobe. Afferents from the mammillary body and other limbic structures, efferents to the cingulate gyrus. Centromedian nucleus (CM).  The largest of the intralaminar nuclei (so called because they are embedded in the internal medullary lamina); afferents from the globus pallidus, efferents to the striatum (with branches projecting diffusely to widespread cortical areas). Dorsomedial nucleus (DM).  Interconnections with prefrontal association cortex and parts of the limbic lobe. Lateral dorsal nucleus (LD).  Efferents to the posterior part of the cingulate gyrus; in many ways an extension of the anterior nucleus. Lateral geniculate nucleus (LGN).  The thalamic relay nucleus for vision. Afferents from the retina via the optic tract, efferents to primary visual cortex above and below the calcarine sulcus. Lateral posterior nucleus (LP).  Interconnections, similar to those of the pulvinar, with posterior association cortex. Medial geniculate nucleus (MGN). The thalamic relay nucleus for hearing. Afferents from the inferior colliculus via the brachium of the inferior colliculus, efferents to auditory cortex in the transverse temporal gyri. Parafascicular nucleus (PF).  An intralaminar nucleus with connections similar to those of the centromedian nucleus. Pulvinar.The largest thalamic nucleus, interconnected with parietal-occipital-temporal association cortex. Reticular nucleus. An unusual thalamic nucleus with no projections to the cortex. Afferents from the thalamus and cerebral cortex, GABAergic efferents back to the thalamus. Ventral anterior nucleus (VA).  A thalamic relay nucleus for the motor system. Afferents from the globus pallidus and cerebellum, efferents to motor areas of cortex. Ventral lateral nucleus (VL).  A thalamic relay nucleus for the motor system. Afferents from the cerebellum and globus pallidus, efferents to motor areas of cortex.

Glossary Ventral posterolateral nucleus (VPL).  The thalamic relay nucleus for somatic sensation from the body. Afferents from the medial lemniscus and spinothalamic tract, efferents to somatosensory cortex in the postcentral gyrus. Ventral posteromedial nucleus (VPM).  The thalamic relay nucleus for somatic sensation from the head and for taste. Afferents from the trigeminal regions of the medial lemniscus and spinothalamic tract and from the nucleus of the solitary tract; efferents to somatosensory cortex in the postcentral gyrus and to gustatory cortex in and near the insula.

Third ventricle.  The single, median, vertically oriented cavity of the diencephalon, separating the thalamus and hypothalamus of the two hemispheres. The third ventricle is confluent anteriorly with both lateral ventricles through the interventricular foramina and posteriorly with the aqueduct and has four small outpocketings: Infundibular recess.  Leads into the hollow infundibulum. Optic recess.  Small recess just above and anterior to the optic chiasm. Pineal recess.  Leads into the stalk of the pineal gland. Suprapineal recess.  An outpocketing of the roof of the third ventricle just anterior to the pineal gland. Interthalamic adhesion

Reticular nucleus

267

Suprapineal recess

Internal medullary lamina External medullary lamina

Anterior nucleus VA

Internal medullary lamina

Optic & infundibular recesses

VL

Internal capsule

DM

(posterior limb)

VPL Pulvinar

Anterior nucleus VA

Internal capsule (posterior limb)

VL

Internal medullary lamina

Pineal recess

Transverse fissure.  An extension of subarachnoid space, situated above the roof of the third ventricle and containing the internal cerebral veins. We use the term in a more extended sense in this book: to refer to the long slit intervening between the cerebral hemispheres and structures below them—the cleft normally occupied by the tentorium cerebelli, continuing into the superior cistern, and from there into the subarachnoid space above the roof of the third ventricle.

DM

VPL CM ar

Pulvin

Reticular nucleus VL External medullary lamina VPL Internal capsule (posterior limb)

VPM

Reticular nucleus

Pulvinar LGN MGN

DM CM

Transverse temporal (Heschl’s) gyri. Gyri (often two) that run transversely across the lower bank of the lateral sulcus. The location of primary auditory cortex.

268

Glossary

Trapezoid body. Auditory fibers from the cochlear nuclei to the contralateral superior olivary nucleus or lateral lemniscus that cross the midline in a trapezoid-shaped area of the pontine tegmentum.

Motor

Main sensory

Spinal nucleus & tract

Trigeminal tracts.  Mesencephalic.  Processes of cell bodies in the adjacent mesencephalic trigeminal nucleus that send one branch to innervate mechanoreceptors in and around the mouth, and others to central termination sites such as the trigeminal main sensory nucleus. Triangular part (of the inferior frontal gyrus).  The middle of the three parts of the inferior frontal gyrus, the most inferior of three longitudinally oriented gyri in the anterior part of the frontal lobe*. In the dominant hemisphere, it forms the anterior half of Broca’s area. Trigeminal nerve.  The 5th cranial nerve, emerging anterolaterally from the basal pons. The trigeminal nerve conveys somatosensory (and some chemosensory) fibers from the ipsilateral half of the head, as well as efferents to ipsilateral muscles of mastication. Motor root.  Small, anterior root containing efferent fibers that distribute through the mandibular division of the nerve. Sensory root.  Massive, posterior root containing afferent fibers that arrive through all three divisions of the nerve. Motor Sensory

Trigeminal nuclei.  Main sensory.  Termination site of large-diameter afferents (the equivalent of a posterior column nucleus for the trigeminal system). Most of its efferents project to the contralateral VPM via the medial lemniscus; some, however, project to the ipsilateral VPM via the dorsal trigeminal tract. Mesencephalic. The cell bodies of primary afferents from muscle spindles in muscles of mastication and from other oral mechanoreceptors. Motor.  Motor neurons for ipsilateral muscles of mastication. Spinal.  The termination site of the spinal trigeminal tract. The most caudal part of the nucleus (in the caudal medulla) looks like the spinal posterior horn, has a component similar to the substantia gelatinosa, and processes pain and temperature information. Its efferents project to VPM (and other thalamic nuclei) through the spinothalamic tract.

Spinal.  Central processes of primary afferents from the ipsilateral side of the face, conveying information about pain and temperature (and some tactile information) to the spinal trigeminal nucleus*. Trochlear nerve.  The 4th cranial nerve, emerging as an alreadycrossed small bundle from the posterior aspect of the midbrain, just caudal to the inferior colliculus. The trochlear nerve innervates the superior oblique, which helps to intort the eyeball and turn it downward and laterally.

Trochlear nucleus.  Motor neurons for the contralateral superior oblique muscle, located in the caudal midbrain just caudal to the oculomotor nucleus. Trochlear axons exit the paired nuclei, turn caudally in the overlying periaqueductal gray, arch posteriorly to decussate (like old-time ice tongs used to handle large blocks of ice), and leave the brainstem at the pons-midbrain junction.

269

Glossary Tuber cinereum. A low mound of gray matter on the inferior surface of the hypothalamus, bounded by the optic chiasm, optic tracts, and anterior edge of the mammillary bodies. The tuber cinereum contains the median eminence and the beginning of the infundibulum and is a region of great importance in hypothalamic hormonal regulation of the anterior pituitary.

Vagus nerve.  The 10th cranial nerve, emerging as a series of filaments from a groove dorsal to the olive. The vagus has diverse components: efferents to muscles of the pharynx and larynx arise from nucleus ambiguus in the medulla and mediate swallowing and phonation; efferents to parasympathetic ganglia for thoracic and abdominal viscera arise from the dorsal motor nucleus of the vagus and nucleus ambiguus in the medulla; afferent fibers mediate general visceral sensation, taste from the epiglottis, and cutaneous sensation in and near the outer ear. IX X

XI

Uncus.  A medial protuberance from the anterior end of the parahippocampal gyrus caused by the underlying amygdala and anterior end of the hippocampus. The proximity of its surface to the adjacent cerebral peduncle can cause clinical problems during cerebral edema or as a result of space-occupying masses.

Provided by Dr. Norman Koelling, University of Arizona

XII

Vein of Galen. See great vein*. Venous angle.  The point at which the newly formed internal cerebral vein turns sharply caudally as it leaves the interventricular foramen. This is an important radiological landmark indicating the location of the genu of the internal capsule and the anterior end of the thalamus.

Internal cerebral veins

Vagal trigone.  A small elevation in the floor of the caudal fourth ventricle forming a narrow triangle just lateral to the hypoglossal trigone. Each vagal trigone is a fusiform swelling produced by the underlying dorsal motor nucleus of the vagus.

Provided by Dr. Raymond Carmody, University of Arizona

Ventral amygdalofugal pathway.  A massive but loosely organized fiber bundle running transversely in the basal forebrain. It interconnects the amygdala with the hypothalamus, septal nuclei, thalamus, and even the brainstem, and is thus an important pathway of the limbic system. The name is somewhat misleading, because the pathway contains fibers traveling both from and to the amygdala.

270

Glossary

Ventral anterior nucleus (VA). See thalamus*. Ventral lateral nucleus (VL). See thalamus*. Ventral pallidum.  A limbic extension of the globus pallidus, located beneath the anterior commissure, with inputs from the ventral striatum. The ventral pallidum is part of a basal ganglia circuit similar to that involved in motor functions, but in this case has limbic inputs (amygdala, hippocampus → ventral striatum → ventral pallidum) and outputs (via the dorsomedial nucleus of the thalamus) to prefrontal and orbital cortex.

Vertebral artery.  One of the two major arteries that supply each side of the CNS (see also internal carotid artery). The vertebral artery originates as the first branch of the subclavian, runs cranially through foramina in cervical vertebrae, enters the base of the skull through the foramen magnum, and ascends along the medulla. At the pontomedullary junction it unites with its contralateral counterpart to form the basilar artery. The vertebral artery and its posterior inferior cerebellar branch (PICA) supply blood to the medulla and inferior part of the cerebellum, and it supplies the cervical spinal cord via the posterior and anterior spinal arteries.

Posterior cerebral a. Superior cerebellar a. Basilar AICA PICA

Ventral posterolateral nucleus (VPL). See thalamus*. Ventral posteromedial nucleus (VPM). See thalamus*. Ventral root.  The anterior (motor) root of a spinal nerve, coalescing from a variable number of unevenly spaced rootlets that depart the spinal cord along its anterolateral sulcus.

Dorsal root

Provided by Dr. Norman Koelling, University of Arizona

Ventral striatum.  The primarily limbic subdivision of the striatum, comprising nucleus accumbens and adjacent parts of the caudate nucleus and putamen. Ventral tegmental area.  An unpaired region of the midbrain medial to the compact part of the substantia nigra*, containing dopaminergic neurons that project to various limbic and neocortical areas. Vermis.  Midline, sinuous (vermis is Latin for “worm”) zone of the cerebellum* between the two cerebellar hemispheres. The vermis includes a representation of the trunk conveyed by the spinocerebellar tracts; its outputs, primarily through the fastigial nucleus, reach the vestibular nuclei and reticular formation.

Vestibular nuclei.  Four elaborately subdivided secondary sensory nuclei of the vestibular division of the 8th cranial nerve in the floor of the fourth ventricle, extending through much of the medulla and into the caudal pons. They reach their greatest extent near the pontomedullary junction, medial to the inferior cerebellar peduncle. Collectively the vestibular nuclei project to the nuclei of extraocular muscles (mostly via the medial longitudinal fasciculus), the cerebellum, the reticular formation, and the spinal cord: Inferior.  Peppered with small bundles of vestibular primary afferents that run through it. Lateral.  Origin of the lateral vestibulospinal tract to ipsilateral extensor motor neurons. Medial.  Origin of the medial vestibulospinal tract, projecting bilaterally to cervical motor neurons. Superior.  Ascending and descending connections with nuclei of extraocular muscles (other vestibular nuclei also share in this).

Glossary Vestibulocochlear nerve.  The 8th cranial nerve, emerging anterolaterally from the brainstem in the cerebellopontine angle. It has vestibular and cochlear divisions innervating hair cells in vestibular organs (semicircular ducts and maculae of the utricle and saccule) and the auditory spiral organ of Corti in the cochlear duct, respectively.

CN VII CN VII

271

Zona incerta. A small sheet of gray matter interposed between the subthalamic nucleus and thalamus, enveloped by efferent fibers of the globus pallidus. The zona incerta has widespread connections, including direct inputs to cerebral cortex, but its function is largely unknown.

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INDEX Page numbers followed by “f” indicate figures.

A Abducens nerve (CN VI), 10f–11f, 18f–21f, 140–144, 144f Abducens nerve fibers, 42f Abducens nucleus, 34f–37f, 42f, 116f–119f, 140f, 144–145, 144f Abscess, 226f Accessory nerve (CN XI), 2f–3f, 18f–21f, 145–150, 145f–146f Accessory nerve fibers, 30f Accessory nucleus, 34f, 38f, 145f–146f Acetylcholine, 180–182, 182f AD. see Alzheimer disease (AD) ALS. see Amyotrophic lateral sclerosis (ALS) Alveus, 173–174, 173f, 179f, 181f Alzheimer disease (AD), 230, 230f–231f Alzheimer plaques, 230f–231f Ambient cistern, 188f–189f Ammon’s horn, 174–178 Amygdala, 1, 53f, 64f–67f, 79f, 86f–91f, 103f, 110f–113f, 134–136, 134f, 136f–137f, 150–151, 153–154, 170–179, 170f, 172f–173f, 176f, 178f, 182–184, 182f–186f, 195f, 199f, 202f–203f afferents to, 174f–175f efferents from, 176f–177f reconstruction of, 103f reconstructions of, 50f–51f Amyotrophic lateral sclerosis (ALS), 234, 234f Anaplastic astrocytomas, 218f Aneurysm, angiogram of, 214f Angiography, 205 anterior cerebral artery, 207f anterior cerebral branches, 207f anterior communicating artery, 207f anterior inferior cerebellar artery, 211f basilar artery, 210f confluence of the sinuses, 209f internal carotid artery, 205, 206f–207f internal cerebral vein, 209f internal jugular vein, 209f, 213f middle cerebral artery, 205f ophthalmic artery, 205f, 207f posterior cerebral artery, 211f posterior inferior cerebellar artery, 211f sigmoid sinus, 209f straight sinus, 209f, 213f superior cerebellar artery, 211f superior sagittal sinus, 205f, 208f–209f, 213f transverse sinus, 213f venous angle, 209f vertebral, 212f artery, 210f Angular gyrus, 6f–9f, 200f–202f Ansa lenticularis, 65f, 90f–93f, 112f–115f, 152, 152f coronal section of, 64f Anterior calcarine sulcus, 96f–101f Anterior cerebral artery, 10f–13f, 60f, 62f, 64f, 66f, 68f, 70f, 72f, 74f, 76f, 86f–101f, 116f–121f areas supplied by, 110f–123f imaging of, 190f–191f, 207f, 214f perforating branches of, 90f–97f Anterior cerebral branches, 88f–99f Anterior choroidal artery, 10f–11f, 86f–91f, 94f–101f, 207f areas supplied by, 108f–115f Anterior cingulate cortex, 174–178

Anterior commissure, 12f–15f, 53f, 62f, 65f, 79f, 88f–93f, 110f–123f, 134–136, 137f, 172f–173f, 180, 193f, 195f, 199f–200f, 203f coronal section of, 62f olfactory component, 61f reconstructions of, 50f–51f Anterior communicating artery, 12f–13f, 207f Anterior corticospinal tract, 29f–30f, 128–132, 130f Anterior horn motor neurons, 130f Anterior horns, 23, 24f–25f motor neurons, 26f, 29f–30f Anterior inferior cerebellar artery (AICA), 10f–11f, 86f–87f, 211f areas supplied by, 33f, 108f–123f Anterior limb, 168–170, 168f–169f Anterior nucleus, 63f, 65f, 168f, 170–171, 172f, 180 Anterior olfactory nucleus, 134–136, 137f Anterior perforated substance, 134–136 Anterior pituitary, 184–186 Anterior root. see Ventral root Anterior spinal artery (ASpA), 2f–3f, 10f–11f, 26f areas supplied by, 33f, 116f–123f Anterior spinocerebellar tract, 27f–30f, 38f–43f, 158f Anterior white commissure, 24f–25f, 27f Anterolateral system, 38f–47f, 128, 128f–129f, 132f Aqueduct (of Sylvius), 12f–13f, 16f–17f, 35f–37f, 196f–197f, 199f Arachnoid, 2f–3f Arachnoid granulations, 6f–7f Area postrema, 20f–21f, 120f–123f Arterial inflow, 171f Association areas, 150–151, 174–182, 174f, 176f, 178f Astrocytomas, 215f–216f anaplastic, 218f diffuse, 217f gemistocytic, 217f infiltrating, 217 pilocytic, 215f–216f Auditory cortex, 138, 138f, 164f, 168f, 176f Auditory system, 138f–139f Axial sections, 79 B “Bare-bones” approach, 125, 125f Basal forebrain, 63f, 65f, 88f–91f, 114f–115f, 182–183 Basal ganglia, 1, 146–150, 150f Huntington disease in, 233 Basal nucleus (of Meynert), 63f, 65f, 88f–89f, 112f–115f, 182–183, 182f Basal pons, 12f–13f, 31, 35f–37f, 49f, 72f, 74f, 76f, 86f–87f, 114f–115f, 128–132, 130f, 146–150, 188f, 190f, 196f, 198f–199f, 203f Basal vein (of Rosenthal), 122f–123f, 209f Basilar artery (BA), 2f–3f, 10f–11f, 44f, 70f, 72f, 74f, 76f, 86f–93f, 118f–123f areas supplied by, 33f, 114f–123f branches of, 46f imaging of, 190f, 210f–211f Basiocciput, 188f, 190f Basket cells, 157f axon, 157f Biphasic pilocytic astrocytoma, 215f–216f

Blink reflex, 132–134 Blood-brain barrier, 204f Bodian staining, 215 Body, of fornix, 173–174, 173f Bone, 187f Brachium of inferior colliculus, 35f–37f, 46f, 138, 164f of superior colliculus, 35f–37f, 143f Brains, 4f–5f coronal sections of, 53 CT images of, 188f ependymoma in, 221f hemisected, 53f hemisphere, 8f–9f inferior surface of, 10f–11f three-dimensional reconstructions of, 53f Brainstem, 1, 1f, 4f–5f, 31, 31f–37f, 170–171, 174f, 176f, 183 central pontine myelinolysis in, 229f long tracts of, 125 medulloblastoma in, 222f–223f reconstruction of, 49, 49f–51f sensory systems, 125 Brainstem nuclei, 174–178 Branchial arches, 144–145 Bunina bodies, in amyotrophic lateral sclerosis, 234f C C-shaped cerebral structures, 49, 49f C-shaped course, 173–174 C-shaped growth, 172–173 CA1 pyramidal cells, 180–182 CA3 pyramidal cells, 180–182 Calcarine sulcus, 12f–15f, 114f–121f, 203f Callosomarginal artery, 120f–121f Catecholamine, 182–184 Cauda equina, 2f–3f Caudal midbrain, 185f Caudal pons, 185f Caudate nucleus, 53f, 62f, 66f, 68f, 70f, 72f, 74f, 79f, 103f, 108f–117f, 150–151, 150f–152f, 153–154, 168f, 173–174, 173f, 182f, 184, 184f, 187f, 189f, 191f, 194f–197f, 200f–201f, 203f body of, 63f–65f, 67f, 69f, 71f, 73f, 75f–77f, 110f–113f coronal section of, 76f head of, 60f–61f, 63f, 88f–101f, 112f–117f, 168–170, 194f in Huntington disease, 233f reconstructions of, 49, 49f–51f, 103f tail of, 67f, 69f, 71f, 73f, 75f–77f, 92f–101f, 108f–113f Caudate/putamen gray bridges, 100f–101f, 112f–113f Cavernous sinus, 190f, 205f, 207f Central canal, 23, 26f, 29f–30f, 38f–39f Central nervous system (CNS), 1 oligodendroglioma in, 220f Central pontine myelinolysis (CPM), 229, 229f Central sulcus, 1f, 4f–7f, 12f–13f, 50f–51f, 108f–121f, 196f–197f, 201f top of, 203f Central tegmental tract, 40f–47f, 86f–93f, 116f–119f, 134f, 162, 162f, 183 Central vision, 142f

273

274

Index

Centromedian nucleus, 69f, 71f, 150–151. see also Thalamus Cerebellar cortex, 154–155, 157f, 158–160, 160f Cerebellar efferents, 152 Cerebellar peduncles, 155f–156f, 162–168 Cerebellothalamic fibers, 47f, 69f, 92f–93f, 114f–121f Cerebellum, 1, 2f–3f, 10f–11f, 16f–19f, 108f–123f, 154–155, 155f–156f, 183, 188f, 197f–199f, 202f–203f, 211f, 213f afferents to, 158f–159f anterior lobe of, 110f–123f, 154–155, 155f cortex of, 40f–41f, 43f demyelination of, 228f dentate nucleus, 92f–93f efferents from, 160f–163f fissures, 154–155 flocculus of, 4f–7f, 10f–11f, 18f–21f, 49f, 198f hemisphere(s), 2f–5f, 12f–13f, 49f, 86f–101f, 155–157, 155f, 188f, 190f, 197f–199f, 202f–203f, 207f lingula, 20f–21f medulloblastoma in, 222f–223f nodulus of, 122f–123f pilocytic astrocytoma in, 215f–216f planes of, 156f posterior lobe of, 108f–123f, 154–155, 155f posterolateral fissure of, 154–155, 155f primary fissure of, 4f–5f, 108f–123f, 154–155, 155f reconstructions of, 49, 49f–51f tonsil of, 114f–121f, 188f, 190f, 197f–198f, 203f vermis of, 2f–5f, 12f–13f, 86f–101f, 155–157, 155f–156f, 160, 188f, 190f, 197f–199f, 203f Cerebral aqueduct, 73f, 75f, 77f, 92f–95f, 122f–123f Cerebral artery anterior, 187f middle, 187f posterior, 187f Cerebral cortex, 159f Alzheimer disease in, 230f–231f granular layer of, 31 oligodendroglioma in, 220f Cerebral hemispheres, 1, 6f–7f, 134–136 Cerebral peduncle, 12f–13f, 16f–17f, 20f–21f, 31, 35f–37f, 45f–47f, 50f–51f, 68f–75f, 88f–91f, 114f–117f, 128–132, 130f, 146–150, 158f–159f, 162–168, 168f–169f, 188f, 196f, 199f in amyotrophic lateral sclerosis, 234f Cerebrospinal fluid, 187f, 193f Cervical dorsal root, 18f–21f Cervical segment, spinal cord, 29f–30f Cervical ventral roots, 10f–11f, 18f–19f Choroid fissure, 110f–113f Choroid plexus, 10f–13f, 18f–19f, 62f, 64f, 66f, 68f–76f, 88f–101f, 108f–119f, 122f–123f, 156f, 179f calcified, 187f fourth ventricle, 35f–37f, 40f–41f, 190f glomus, 110f–113f, 197f, 202f in interventricular foramen, 120f–123f lateral ventricle, 188f–191f, 194f–197f, 199f–201f third ventricle, 211f roof of, 122f–123f Choroidal vein, 70f Cingulate gyrus, 12f–15f, 53f, 60f, 62f, 64f, 66f, 68f, 70f, 72f, 74f, 76f, 79f, 92f–101f, 116f–117f, 164f, 171f–172f, 174f, 176f, 178f, 189f, 194f–197f, 200f–201f, 203f isthmus of, 98f–101f, 172f, 197f, 200f Cingulate sulcus, 12f–15f, 114f–123f marginal branch of, 114f–123f, 203f Cingulum, 114f–115f, 178–179, 178f, 182–183, 182f Circle of Willis, 190f, 205f Cisterna magna, 197f–198f, 203f Clarke’s nucleus, 24f–25f, 27f–28f, 158f Claustrum, 61f, 63f, 65f, 67f, 69f, 88f–99f, 108f–113f, 182–183

Climbing fibers, 155–158, 157f–158f Clinical imaging, 187–205 Clinoid processes, 190f anterior and posterior, 188f Coccygeal, 2f–3f Cochlear division, of cranial nerve VIII, 136–138, 138f Cochlear nucleus, 40f–41f Collateral sulcus, 4f–5f, 14f–15f, 66f, 68f, 70f, 72f, 74f, 86f–101f, 108f–109f, 199f Columns, of fornix, 173–174, 173f, 180 Compact part (SNc), of substantia nigra, 153–154, 153f Computed tomography (CT), 187–193 with contrast, 187–193, 190f–192f for intracranial pathology, 192f Confluence of the sinuses, 191f, 199f, 203f, 209f, 213f Conus medullaris, 2f–3f Cornu ammonis (CA), 174–178 Cornu ammonis (CA) fields, 178–179 Corona radiata, 50f–51f, 100f–101f, 162–168, 169f Corpus callosum, 1, 4f–5f, 12f–15f, 53f, 79f, 116f–123f, 173–178, 189f, 194f, 200f–201f, 203f, 207f body of, 60f, 62f, 64f, 66f, 68f, 70f, 72f, 98f–101f, 118f–123f, 189f, 191f, 193f–197f, 201f, 203f genu of, 12f–13f, 90f–101f, 116f–123f, 189f, 194f, 200f, 203f glioblastoma in, 219f rostrum of, 12f–13f, 90f–93f, 194f splenium of, 74f, 76f, 116f–123f, 189f, 191f, 197f, 200f, 203f Cortex, 155–157 Cortical atrophy, in Alzheimer disease, 230f–231f Cortical neuron, 150f–151f, 154f Corticobulbar fiber, 42f–44f, 128–132 Corticobulbar tract, 146–150, 146f–147f Corticopontine fiber, 42f–44f, 128–132, 146–150 Corticopontine neurons, 168f Corticospinal fiber, 42f–44f, 146–150 Corticospinal nucleus, 168f Corticospinal tract, 31, 31f–32f, 35f–37f, 128–132, 130f–131f, 146–150 in amyotrophic lateral sclerosis, 234f CPM. see Central pontine myelinolysis (CPM) Cranial nerve nuclei branchial arch origin and, 145f skeletal muscle and, 144f Cranial nerves, 31, 31f–32f, 34f Cribriform plate, of ethmoid bone, 134–136 Crus, of fornix, 173–174, 173f Cuneate tubercle, 20f–21f Cuneus, 14f–15f D Deep cerebellar nuclei, 42f, 90f–91f, 155–160 Demyelinating syndromes, 227–229 Demyelination, of cerebellum and pons, 228f Dentate gyrus, 174–182, 181f Dentate nucleus, 42f, 88f–91f, 112f–115f, 160, 160f–162f Denticulate ligament, 2f–3f, 18f–19f Descending limb, 162, 162f Diencephalon, 1, 1f, 31f, 88f–89f reconstruction of, 49, 49f–51f Diffuse astrocytoma, 217f Direct route, 154–155 Dopamine, 153–154, 183–184, 184f Dorsal accessory nucleus, 40f Dorsal cochlear nucleus, 114f–115f, 136–138, 138f Dorsal longitudinal fasciculus, 39f–47f, 120f–121f, 170, 170f–171f, 183 Dorsal motor nucleus, 35f–37f of vagus, 39f–40f, 134, 134f, 148f, 183, 183f

Dorsal motor nucleus (X), 116f–117f Dorsal raphe nucleus, 44f–45f Dorsal root, 2f–3f C3, 2f–3f C8, 2f–3f Dorsal root ganglia, 126f, 128f Dorsal rootlet, 26f, 28f–30f Dorsal trigeminal tract, 132f Dorsomedial nucleus, 65f, 67f, 69f, 71f, 152–153, 168f Dura mater, 2f–3f, 191f–192f, 195f, 204f E Edinger-Westphal nucleus, 47f, 148f Entorhinal cortex, 134–136, 136f–137f, 178–180, 178f, 181f, 183 Ependymoma, 221f Ethmoid bone, cribriform plate of, 134–136 Ethmoidal air cells, 187f Ex vacuo hydrocephalus, 230, 230f–231f External acoustic meatus, 188f, 190f External capsule, 63f, 108f–109f, 182–183, 182f External medullary lamina, 65f, 67f, 69f, 71f, 73f, 75f Extraocular muscles, 194f Extreme capsule, 63f, 108f–109f Eye, 187f, 207f F Facial colliculus, 20f–21f, 145 Facial motor nucleus, 145, 145f–146f Facial nerve (CN VII), 10f–11f, 18f–21f, 42f, 116f–117f, 134, 134f, 145–150, 145f–146f internal genu, 42f internal genu of, 145f Facial nucleus, 42f Falx cerebri, 189f, 191f–192f, 195f, 204f Fasciculus cuneatus, 20f–21f, 24f–25f, 29f–30f, 35f–39f, 116f–119f, 126, 126f–127f Fasciculus gracilis, 20f–21f, 24f–25f, 29f–30f, 35f–38f, 118f–123f, 126, 126f–127f Fastigial nucleus, 42f, 90f–91f, 118f–121f, 160, 160f–162f Fiber entry zone, 126f Filum terminale, 2f–3f Fimbria (of the hippocampus), 110f–113f, 173–174, 173f, 181f, 199f, 202f fornix fibers, 71f, 73f, 75f–77f, 90f–101f Flocculonodular lobe, 140, 154–155, 160 Flocculus, 140f, 155f–156f Folium, 155–157, 157f Foramen magnum, 188f, 190f, 198f Foramen of Monro. see Interventricular foramen (of Monro) Forebrain, 10f–11f, 49 Fornix, 14f–15f, 53f, 79f, 114f–123f, 170–171, 170f, 172f, 178–180, 178f, 182–186, 182f, 186f, 195f–197f, 200f, 203f body of, 63f, 65f, 67f, 69f, 71f, 73f, 96f–101f, 118f–123f, 200f column of, 63f, 65f, 67f, 88f–97f, 118f–121f, 200f coronal section of, 76f crus of, 73f, 75f–76f, 114f–121f, 200f precommissural part of, 92f–93f reconstructions of, 49f–51f Fourth ventricle, 35f–37f, 40f–44f, 53f, 79f, 86f–91f, 116f–123f, 145, 188f, 190f, 197f–199f, 203f lateral recess/aperture, 35f–37f, 41f median aperture of, 120f–123f reconstruction of, 103f Frontal cortex, 153–154 oligodendroglioma in, 220f Frontal lobe, 1, 1f–3f, 50f–51f, 188f, 190f glioblastoma in, 219f Frontal operculum, 134 Functional systems, 125–186

Index G Gamma-aminobutyric acid (GABA), 180–182 Ganglion cells, 143f Gemistocytic astrocytoma, 217f Geniculate ganglion, 134f Genu, 168–170, 168f GFAP. see Glial fibrillary acidic protein (GFAP) Glial cells, glioblastoma in, 219f Glial fibrillary acidic protein (GFAP), 215f–216f Glioblastoma, 219f, 220 Glioblastoma multiforme (GBM). see also Glioblastoma magnetic resonance image of, 193f, 204f Gliomatosis cerebri, 218f Globus pallidus, 60f, 62f, 64f, 66f, 68f–69f, 90f–91f, 110f–115f, 146–152, 150f–152f, 189f, 195f–196f, 200f, 203f external segment of, 61f, 63f, 65f, 67f, 92f–97f, 110f–115f, 151–152, 152f, 154–155, 154f internal segment of, 63f, 65f, 67f, 92f–93f, 112f–115f, 151–155, 152f, 154f ventral pallidum of, 114f–115f Glossopharyngeal nerve (CN IX), 10f–11f, 18f–21f, 40f–41f, 134, 134f, 145–150, 145f–146f Glutamate, 180–182 Golgi cell, 157f Gracile tubercle, 20f–21f Granular eosinophilic bodies, in pilocytic astrocytoma, 215f–216f Granular layer, 157, 157f Granule cells, 157, 157f Gray matter, 187f, 193f Great cerebral vein (of Galen), 122f–123f, 191f, 209f, 213f Gustatory afferents, 148f–149f Gustatory cortex, 134, 134f Gustatory sensations, 132–134 Gustatory system, 134f–135f, 136–138 Gyri, 1 Gyrus rectus, 10f–11f, 14f–15f, 18f–19f, 60f, 86f–87f, 122f–123f, 194f, 199f H Habenula, 12f–13f, 20f–21f, 71f, 96f–97f, 118f–121f, 172f Habenular commissure, 122f–123f Habenulointerpeduncular tract, 71f, 92f–97f, 116f–121f, 172f Hair cells, 136–140 HD. see Huntington disease (HD) Hematoxylin and eosin (H&E) stains, in neuropathology, 215 Heschl, transverse temporal gyri of, 138 Hippocampus, 53f, 66f, 68f–70f, 72f, 74f, 76f, 79f, 86f–101f, 103f, 108f–113f, 150–151, 170–178, 172f–173f, 176f, 178f, 182–186, 182f–186f, 195f–197f, 199f, 202f afferents to, 178f–179f alveus of, 108f–109f anterior end of, 68f dentate gyrus of, 71f, 73f, 75f, 77f, 86f–101f, 108f–113f efferents from, 180f–181f hippocampus proper, 71f, 73f, 75f, 77f, 108f–113f reconstruction of, 103f reconstructions of, 49f–51f subiculum of, 71f, 73f, 75f, 77f, 86f–101f, 110f–113f Hippocampus proper, 174–179 Histamine, 184–186 Homer-Wright rosettes, 222f–223f Huntington disease (HD), 233, 233f Hydrocephalus, ependymoma in, 221f Hypocretins, 184–186 Hypoglossal motor neurons, 31

Hypoglossal nerve (CN XII), 2f–3f, 10f–11f, 18f–21f, 39f–40f, 140–144, 144f, 146–150 Hypoglossal nucleus, 35f–37f, 39f–40f, 120f–121f, 144f Hypoglossal trigone, 20f–21f Hypothalamic sulcus, 12f–13f Hypothalamus, 1, 12f–13f, 49f, 79f, 90f–93f, 103f, 116f–121f, 134–136, 134f, 168–170, 172–178, 172f, 174f, 183–186, 184f–185f, 188f, 195f, 203f afferents to, 170f anterior region of, 88f–89f, 116f–121f efferents from, 171f mammillary body, 53f, 79f modulatory outputs of, 186f pilocytic astrocytoma in, 215f–216f posterior region of, 67f, 88f–89f, 116f–121f reconstruction of, 103f tuberal region of, 53f, 65f, 79f, 86f–89f, 116f–121f I Indirect route, 154–155 Inferior anastomotic vein (of Labbé), 209f Inferior brachium, 114f–115f Inferior capsule, posterior limb of, 92f–93f Inferior cerebellar peduncle, 20f–21f, 35f–37f, 40f–42f, 86f–87f, 114f–115f, 140f, 156f, 158–160, 158f, 162–168, 162f, 198f Inferior colliculus, 12f–13f, 16f–17f, 20f–21f, 31, 35f–37f, 45f–47f, 92f–95f, 116f–123f, 138, 138f, 197f, 203f brachium of, 20f–21f, 35f–37f, 46f, 77f, 92f–95f, 138, 164f Inferior frontal gyri(us), 4f–9f, 50f–51f, 60f, 62f, 194f–195f, 199f, 201f–202f Inferior ganglion, 134f Inferior horn, of lateral ventricle, 188f, 190f, 195f, 199f Inferior olivary complex, 40f Inferior olivary nucleus, 35f–37f, 39f–41f, 116f–121f, 157–158, 158f, 162, 162f Inferior parietal lobule, 4f–5f Inferior temporal gyrus, 6f–15f, 18f–19f, 50f–51f, 60f, 62f, 64f, 66f, 68f, 70f, 72f, 74f, 86f–91f, 195f–196f, 199f, 202f Inferior thalamic peduncle, 92f–93f, 116f–117f Inferior vestibular nucleus, 40f, 140f Infiltrating astrocytomas, 217 Infundibulum, 4f–5f, 10f–13f, 49f, 171–172, 171f, 188f, 190f Insula, 14f–15f, 60f, 62f, 64f, 66f, 68f, 72f, 88f–95f, 98f–99f, 108f–109f, 134, 194f–196f, 199f–200f, 202f, 205f, 207f Intermediate gray, 23 Intermediate zone, 160 Intermediolateral cell column, 148f Internal arcuate fibers, 35f–41f, 116f–123f Internal capsule, 103f, 110f–115f, 128–132, 146–153, 153f, 158f–160f, 162–168, 168f–169f, 187f, 189f, 191f, 194f–196f, 200f, 203f anterior limb of, 60f–61f, 88f–99f, 189f, 191f, 194f–195f, 200f axial section of, 168f genu of, 62f–63f, 92f–99f, 114f–115f, 189f, 191f, 195f, 200f posterior limb of, 64f–69f, 92f–99f, 112f–113f, 126f, 128f, 130f, 132f, 134f, 168f–169f, 189f, 191f, 195f–196f, 200f, 203f reconstruction of, 50f–51f retrolenticular part of, 94f–97f, 142f, 168–170, 169f, 200f sublenticular part of, 68f–69f, 110f–111f, 138f, 142f, 168–170, 169f, 196f Internal carotid artery, 2f–3f, 10f–11f, 86f–87f, 195f, 198f–199f, 202f–203f areas supplied by, 116f–123f imaging of, 205f, 207f, 214f perforating branches, 86f–87f

275

Internal cerebral vein, 12f–13f, 65f, 67f, 69f, 71f, 73f, 75f, 98f–101f, 118f–123f, 191f, 199f, 209f Internal genu, of facial (VII) nerve, 145, 145f Internal jugular vein, 198f, 202f, 209f, 213f Internal medullary lamina, 67f Interpeduncular cistern, 196f, 199f Interpeduncular fossa, 88f–89f Interposed nucleus, 42f, 88f–91f, 116f–117f, 160, 160f–162f Interthalamic adhesion, 12f–13f, 65f, 94f–97f Interventricular foramen (of Monro), 12f–13f, 63f, 94f–95f, 191f, 203f Intralaminar nuclei, 150–151 Intraparietal sulcus, 4f–7f Isthmus (of the cingulate gyrus), 197f, 200f L Lamina terminalis, 12f–13f, 90f–91f, 122f–123f Large fiber entry zone, 26f–30f Lateral corticospinal tract, 27f–30f, 128–132, 130f, 146f Lateral cuneate nucleus, 39f–40f, 158f Lateral division, of spinal cord, 126–128 Lateral dorsal nucleus, 67f, 69f Lateral funiculus, 23, 23f–25f Lateral geniculate nucleus, 71f, 73f, 75f, 92f–93f, 142f–143f, 168f Lateral horn, 28f Lateral lemniscus, 20f–21f, 35f–37f, 42f–45f, 88f–93f, 116f–119f, 138, 138f Lateral olfactory tract, 112f–115f, 134–136, 136f–137f, 174–178 Lateral posterior nucleus, 71f Lateral rectus, 188f motor neurons, 144–145 Lateral sulcus (of Sylvius), 1f, 4f–7f, 60f, 62f, 64f, 66f, 68f, 70f, 72f, 74f, 86f–91f, 96f–101f, 189f, 194f, 202f, 207f Lateral ventricle, 53f, 62f, 79f, 108f–119f, 122f–123f, 173–178, 188f–191f, 194f–197f, 199f–201f anterior horn of, 60f, 90f–101f, 114f–119f, 122f–123f, 189f, 191f, 194f–195f, 200f atrium (or trigone), 110f–113f, 189f, 191f, 197f, 199f–200f body of, 64f, 66f, 68f, 70f, 72f, 74f, 76f, 114f–119f, 189f, 191f, 196f, 200f–201f inferior horn of, 66f, 68f, 70f, 72f, 74f, 76f, 86f–101f, 108f–113f, 188f, 190f, 195f, 199f posterior horn of, 110f–113f reconstruction of, 49, 49f–51f, 103f Lateral vestibular nucleus, 42f, 140–144, 140f Lateral vestibulospinal tract, 140–144, 140f Lens, 188f, 190f, 199f, 202f Lenticular fasciculus, 65f, 67f, 92f–93f, 114f–115f, 152, 152f Lenticular nucleus, 168–170, 168f, 173–174, 189f Lenticulostriate arteries, 61f, 63f, 65f, 88f–91f, 108f–113f, 207f Leukoencephalopathy, progressive multifocal, 228, 228f Lewy bodies, 232f Limbic areas, 150–151, 171f, 174–178, 184 Limbic cortex, 170–173 Limbic lobe, 1f Limbic system, 1, 171–172, 172f Limen insulae, 14f–15f Lingual gyrus, 14f–15f, 96f–101f Lissauer’s tract, 23, 23f–30f, 128f, 132–134, 132f Locus ceruleus, 35f–37f, 44f, 183, 183f Longitudinal fissure, 1, 2f–5f, 10f–11f, 18f–19f, 60f, 62f, 66f, 68f, 70f, 72f, 74f, 76f, 86f–101f, 189f Lower quadrants, in upper bank, 142f Lower vertical midline, 142f

276

Index

M Magnetic resonance imaging (MRI), 187–193, 187f angiography, 205 axial, 192f, 198f–201f coronal, 194f diffusion tensor imaging, 193f diffusion-weighted, 193–205 intracranial pathology, 204f sagittal and parasagittal, 202f T1-weighted vs. T2-weighted, 193 Main sensory nucleus, 126, 126f, 132, 132f Mammillary bodies, 12f–13f, 20f–21f, 67f coronal section of, 66f Mammillary body, 79f, 88f–89f, 116f–123f, 170–171, 172f, 173–174, 178f, 180, 183–186, 195f, 203f Mammillothalamic tract, 65f, 67f, 88f–93f, 116f–123f, 164f, 170–171, 172f Mandible (condyle), 188f, 190f Mastoid air cells, 187f–188f, 190f Medial accessory nucleus, 40f Medial division, of spinal cord, 125 Medial forebrain bundle, 170–171, 170f–171f, 183–184, 183f–186f Medial geniculate nucleus, 20f–21f, 73f, 75f, 138, 138f, 164f, 168f Medial lemniscus, 31, 31f–32f, 35f–37f, 39f, 41f–47f, 75f, 77f, 86f–93f, 114f–119f, 122f–123f, 126f, 132, 132f, 164f Medial longitudinal fasciculus (MLF), 38f–47f, 77f, 86f–91f, 120f–121f, 140f, 144–145, 144f Medial rectus, 188f motor neurons, 144–145 Medial striate artery, 10f–11f Medial temporal lobe, 172–178 Medial vestibular nucleus, 40f, 140–144 Medial vestibulospinal tract, 140–144, 140f Median eminence, 10f–11f, 171–172, 171f, 184–186 Medulla, 4f–5f, 10f–11f, 18f–19f, 31, 31f, 34f–41f, 188f, 190f, 196f–198f, 203f Medullary pyramids, 31, 146–150 Medulloblastoma, 222f–223f Meningioma, 214f, 224, 224f–225f Mesencephalic nucleus, 126, 126f, 132, 132f Mesencephalic tract, 116f–117f Mesocortical fibers, 184 Mesolimbic fibers, 184 Mesostriatal dopaminergic pathway, 184 Microvascular proliferation, in glioblastoma, 219f Midbrain, 31, 32f, 34f–37f, 45f–47f, 49f, 189f–191f, 203f location of, 211f reticular formation, 172f Middle cerebellar peduncle, 20f–21f, 31f, 42f, 49f, 86f–87f, 156f, 158, 158f–159f, 196f–198f Middle cerebral artery, 10f–11f, 60f, 62f, 64f, 66f, 68f, 70f, 72f, 74f, 76f, 86f–101f, 112f–113f, 195f, 199f areas supplied by, 108f–115f imaging of, 190f, 192f–193f, 204f–205f, 207f, 214f perforating branches of, 88f–101f Middle cerebral branches, 62f, 88f–101f, 108f–111f, 114f–115f, 207f Middle frontal gyrus, 6f–9f, 50f–51f, 60f, 62f, 194f–195f, 201f–202f Middle temporal gyrus, 6f–11f, 18f–19f, 50f–51f, 60f, 62f, 64f, 66f, 68f, 70f, 72f, 74f, 86f–91f, 195f–196f, 199f Midthalamus, 189f Molecular layer, 43f, 157, 157f Monro (foramen of). see Interventricular foramen (of Monro) Mossy fibers, 155–157, 157f Motor areas, 150–151, 158, 184 Motor cortex, 150, 153–154, 158f, 160, 160f, 164f Motor neurons, 23, 23f–30f, 182–183 anterior horns, 26f, 29f–30f

Motor root, 18f–19f Multiple neurofibrillary tangles, Alzheimer disease in, 230f–231f Multiple sclerosis (MS), 227f magnetic resonance imaging in, 204f Muscle, 187f Myelinolysis, central pontine, 229, 229f N Nasal bone, 187f Nasal septum, 198f Necrotic midline cerebellar tumor, 222f–223f Neuritic plaques, Alzheimer disease in, 230f–231f Neurodegenerative diseases, 230–234 Neurofibrillary tangle, Alzheimer disease in, 230f–231f Neurons, 182f–185f Neuropathology, 215–234 Nigrostriatal pathway, 184 Nodulus, 140f, 155f–156f Noradrenergic neurons, 183 Norepinephrine, 182–183, 183f Nucleus accumbens, 50f–51f, 61f, 88f–89f, 114f–117f, 172f, 174–178, 176f, 183, 194f–195f, 199f, 203f Nucleus ambiguus, 34f, 39f–40f, 145f–146f Nucleus cuneatus, 31, 35f–39f, 120f–121f, 126, 126f Nucleus gracilis, 31, 35f–39f, 120f–121f, 126, 126f Nucleus of the solitary tract, 34f, 40f–41f, 116f–119f O Obex, 20f–21f Occipital lobe, 1, 1f–3f, 6f–7f, 213f Occipitotemporal (fusiform) gyrus, 4f–5f, 10f–15f, 64f, 66f, 68f, 70f, 72f, 74f, 86f–97f, 108f–111f, 194f–197f, 202f Oculomotor nerve (CN III), 10f–13f, 20f–21f, 46f, 71f, 86f–87f, 118f–119f, 140–144, 144f, 148f Oculomotor nerve fibers, 88f–89f, 116f–117f, 120f–121f Oculomotor nucleus, 35f–37f, 46f–47f, 73f, 75f, 92f–93f, 120f–121f, 140f, 144f caudal end of, 77f Olfactory branch, 10f–11f Olfactory bulb, 2f–7f, 10f–11f, 14f–15f, 18f–19f, 134–136, 136f–137f, 172f, 174–178, 174f Olfactory epithelium, 137f Olfactory nerve (CN I), 134–136, 137f Olfactory receptor neurons, 134–136 Olfactory receptors, 132–134 Olfactory sulcus, 10f–11f, 18f–19f Olfactory system, 136f–137f Olfactory tract, 2f–5f, 10f–11f, 18f–19f, 60f, 63f, 86f–87f, 134–136, 136f–137f Olfactory tubercle, 134–136, 137f Oligodendroglioma, 220f Olive, 49f, 196f Ophthalmic artery, 205f, 207f Optic chiasm, 4f–5f, 10f–13f, 63f, 79f, 86f–87f, 116f–123f, 142f–143f, 195f, 199f, 203f Optic nerve, 2f–3f, 10f–13f, 63f, 116f–117f, 143f, 194f, 202f–203f damage, 142f Optic radiation, 88f–101f, 142f–143f, 193f damage, 142f Optic tract, 10f–11f, 20f–21f, 65f, 67f, 69f, 71f, 88f–93f, 112f–115f, 142f–143f, 195f–196f, 199f Orbital cortex, 136–138, 170f, 174–178, 174f, 176f Orbital fat, 198f Orbital gyri, 4f–7f, 10f–11f, 18f–19f, 50f–51f, 194f, 199f, 202f Orexins, 184–186 Oxytocin, 171–172

P Pallidothalamic fibers, 116f–117f Parabrachial nuclei, 44f, 134–136, 134f, 170, 174–178 Paracentral lobule, 14f–15f Parafascicular nucleus, 69f, 71f, 150–151 Parahippocampal gyrus, 4f–5f, 10f–11f, 14f–15f, 62f, 64f, 66f, 68f, 70f, 72f, 74f, 76f, 86f–97f, 108f–113f, 134–136, 172f, 174–179, 194f–197f, 199f, 202f Parallel fibers, 157, 157f Parasympathetic ganglion cell, 182f Paraterminal gyrus, 12f–13f Paraventricular nucleus, 171–172, 171f Parenchyma, meningioma in, 224f–225f Parietal lobe, 1, 2f–3f Parietal/occipital/temporal association cortex, 166f Parietooccipital sulcus, 12f–15f, 108f–121f, 200f, 203f Parkinson disease (PD), 232, 232f Parotid gland, 198f, 202f PD. see Parkinson disease (PD) Periamygdaloid cortex, 86f–87f, 134–136, 136f–137f Periaqueductal gray, 35f–37f, 45f–47f, 73f, 75f, 77f, 94f–95f, 118f–119f, 170, 174–178 Periaqueductal gray matter, 128–132, 128f Pericallosal artery, 120f–121f Perilymph, 187f Perineuronal satellitosis, 220f Peripheral vision, 142f Perivascular lymphocytes, in multiple sclerosis, 227f Perivascular pseudorosette, 221f Periventricular gray, 44f Periventricular plaques, in multiple sclerosis, 227f Pilocytic astrocytomas, 215f–216f Pineal gland, 12f–13f, 20f–21f, 73f, 75f, 96f–99f, 118f–123f Piriform cortex, 110f–111f, 134–136, 136f–137f Pituitary gland, 171–172, 188f, 194f–195f, 199f, 203f anterior lobe of, 171–172 posterior lobe of, 171–172 Pituitary portal system, 184–186 Plaques, 232 PML. see Progressive multifocal leukoencephalopathy (PML) Pons, 10f–11f, 18f–19f, 32f, 34f–37f, 42f–44f, 203f demyelination of, 228f pilocytic astrocytoma of, 215f–216f Pontine cistern, 199f Pontine nuclei, 35f–37f, 42f–45f, 158, 158f–159f, 160 Pontocerebellar fibers, 42f–44f Portal veins, 171–172, 171f Postcentral gyrus, 8f–9f, 50f–51f, 108f–113f, 126, 126f, 128, 128f, 200f–201f Postcentral sulcus, 6f–7f Posterior cerebral artery, 10f–11f, 64f, 66f, 68f, 70f, 72f, 74f, 76f, 86f–101f, 116f–117f areas supplied by, 33f, 108f–123f imaging of, 190f–191f, 211f perforating branches of, 88f–101f Posterior cerebral branches, 75f, 86f–89f, 92f–101f, 110f–115f, 211f Posterior column, 26f–27f, 29f, 125 Posterior column-medial lemniscus pathway, 125 Posterior column-medial lemniscus system, 126f Posterior column nuclei, 31, 32f, 35f–37f, 126, 127f, 128–132 Posterior commissure, 12f–13f, 73f, 94f–95f, 118f–123f, 196f, 199f, 203f coronal section of, 72f Posterior communicating artery (PCoA), 10f–11f, 187f, 190f areas supplied by, 33f Posterior funiculus, 23, 23f–25f, 125 Posterior horn, 132–134 of spinal cord, 126–132

Index Posterior horn, spinal cord, 23, 24f–27f, 30f caps of, 24f–25f Posterior inferior cerebellar artery, 10f–11f, 86f–87f areas supplied by, 108f–123f Posterior inferior cerebellar artery (PICA), 211f areas supplied by, 33f branch, 156f posterior inferior cerebellar branches, 40f Posterior inferior cerebellar branches, 2f–3f, 114f–115f, 118f–121f Posterior limb, of internal capsule, 126f, 128f, 130f, 132f, 134f, 168–170, 168f–169f Posterior lobe, 171f Posterior pituitary, 171f Posterior spinal artery, 26f areas supplied by, 33f, 116f–123f Posterior spinocerebellar tract, 24f–25f, 27f–29f, 38f–41f, 158f Postganglionic parasympathetic neurons, 182–183 Postganglionic sympathetic neurons, 182–183 Precentral & postcentral gyri, 202f–203f Precentral gyrus, 6f–9f, 50f–51f, 108f–113f, 128–132, 146–150, 195f, 201f Precommissural fornix, 120f–121f, 180 Precuneus, 14f–15f Prefrontal areas, 171f Prefrontal cortex, 166f, 170–171 Preganglionic autonomic neurons, 170–171, 182–183 Preganglionic sympathetic neurons, 134 Premotor cortex, 128–132, 130f, 146–150, 146f, 158f, 160, 160f, 164f Preoccipital notch, 6f–9f Preoptic area, 90f–91f, 116f–121f Pretectal area, 73f, 75f, 94f–97f Primary brain tumors, 215 Primary motor cortex, 128–132, 130f, 146–150, 146f Primary sensory areas, 174–178 Primary somatosensory cortex, 126, 128 Progressive multifocal leukoencephalopathy (PML), 228, 228f Psammomatous meningioma, 224f–225f Pulvinar, 20f–21f, 73f, 75f, 77f, 166f, 168f Purkinje cell, 43f, 155–157, 157f Purkinje cell axons, 158–160 Purkinje cell dendrites, 157f Putamen, 50f–51f, 53f, 60f–69f, 79f, 88f–99f, 103f, 108f–113f, 150–154, 150f–152f, 182–184, 182f, 184f, 189f, 191f, 194f–196f, 199f–200f, 202f–203f in Huntington disease, 233f reconstruction of, 103f Pyramid, 16f–21f, 38f–41f, 49f, 116f–123f, 128–132, 130f, 146f, 198f Pyramidal decussation, 18f–21f, 31, 35f–38f, 120f–123f, 128–132, 130f, 146–150, 146f R Raphe nuclei, 44f–45f, 128–132, 128f–129f, 184–186, 185f Red nucleus, 16f–17f, 35f–37f, 47f, 71f, 90f–93f, 116f–121f, 153f, 160f, 162, 162f, 196f rostral end of, 69f Reticular formation, 31, 31f–32f, 38f–47f, 128–132, 128f, 134, 134f, 153–154, 162–168, 162f, 182–183, 183f Reticular nucleus, 65f, 67f, 69f, 71f, 73f, 75f Reticular part (SNr), of substantia nigra, 152–155, 153f Retina, 184–186 Retinal ganglion cells, 170 Retrolenticular part, of internal capsule, 142f, 168–170, 169f Rexed laminae, 23 Rhinal sulcus, 4f–5f, 10f–13f Right CN II, 142f

Right optic nerve, central connections of, 142f Right optic tract damage, 142f Right visual cortex damage, 142f Right visual field, 142f Rostral medulla, 183f, 185f Rostral pons, 183f, 185f Rubrospinal tract, 162 S Saccule, 138–140 Sacral parasympathetic nucleus, 148f Sagittal sections, 103 Scalp, 193f Sclerosis, amyotrophic lateral, 234, 234f Semicircular ducts, 138–140 Senile plaques, Alzheimer disease in, 230f–231f Sensory association areas, 174–178 Sensory root, 18f–19f Septal nuclei, 61f, 63f, 92f–97f, 116f–121f, 170f–172f, 173–180, 178f, 182–184, 182f, 184f Septal vein, 12f–13f, 61f, 94f–95f, 209f Septum pellucidum, 12f–13f, 53f, 61f, 63f, 65f, 79f, 94f–99f, 120f–123f, 173–174, 189f, 191f, 195f Serotonin, 184–186, 185f Sigmoid sinus, 187f, 197f–198f, 202f, 209f, 212f Silver stains, in neuropathology, 215 Skull fracture, CT images of, 192f Small fiber entry zone, 26f–30f SN. see Substantia nigra (SN) Solitary tract (and its nucleus), 35f–37f, 39f–42f, 116f–119f, 134, 134f, 148f, 170, 174–178, 183, 183f Somatosensory areas, 158 Somatosensory association cortex, 166f Somatosensory cortex, 126f, 128–132, 130f, 132f, 146f, 150–151, 158f, 164f, 176f Somatosensory system, 136–138 Somatotopic arrangement, 125–128 Sphenoid bone, 187f Sphenoid sinus, 188f, 190f Sphenopetrosal vein, 209f Spinal cord, 23, 158, 160, 170–171, 183, 183f, 186f, 196f, 203f cervical segments of, 23, 23f ependymoma in, 221f fourth sacral segment of, 24f–25f long tracts of, 125 Spinal tract, 116f–117f Spinal trigeminal nucleus, 128, 128f, 132, 132f Spinal trigeminal tract (and nucleus), 35f–42f, 128, 128f, 132–134, 132f Spinal ventral roots, 148f Spinocerebellar tracts, 160 Spinothalamic tract, 24f–26f, 28f–32f, 31, 35f–47f, 75f, 77f, 88f–93f, 114f–115f, 126–128, 170 Spinothalamic tract cells, 129f Spiral ganglion, 136–138, 138f Splenium, 173–178 Stains, in neuropathology, 215 Stellate cells, 157f Straight sinus, 191f, 199f, 203f, 209f, 213f Stria medullaris (of the thalamus), 67f, 69f, 94f–99f, 116f–123f, 172f, 200f Stria terminalis, 63f, 65f, 67f, 69f, 71f, 73f–75f, 88f–101f, 110f–115f, 170–171, 170f–173f, 173–178 coronal section of, 74f Striatum, 146–153, 151f, 154f, 182–186, 185f Subcallosal fasciculus, 88f–101f Subcallosal gyrus, 12f–13f, 90f–93f, 122f–123f Subicular neurons, 180 Subiculum, 174–179 Sublenticular part, of internal capsule, 138f, 142f, 168–170, 169f Subparietal sulcus, 12f–15f, 116f–121f Substantia gelatinosa, 23, 23f–30f, 128–132, 128f, 132f

277

Substantia gelatinosa interneuron, 129f Substantia nigra (SN), 14f–17f, 35f–37f, 46f–47f, 69f, 88f–91f, 114f–119f, 146–153, 151f, 153f–154f, 183–184, 184f, 196f compact part of, 71f, 73f, 75f, 116f–117f, 183–184 in Parkinson disease, 232f reticular part of, 71f, 73f, 75f, 116f–117f, 151–152 Subthalamic fasciculus, 92f–93f, 151–152, 152f Subthalamic nucleus, 67f, 69f, 92f–93f, 114f–115f, 146–154, 152f–154f Sulci, in Alzheimer disease, 230f–231f Sulcus limitans, 20f–21f, 34f–37f, 40f Superficial middle cerebral vein, 209f Superior anastomotic vein (of Trolard), 209f Superior cerebellar artery (SCA), 10f–11f, 74f, 76f, 86f–101f, 211f areas supplied by, 33f, 108f–123f Superior cerebellar branches, 114f–117f Superior cerebellar peduncle, 12f–13f, 20f–21f, 35f–37f, 42f–45f, 75f, 88f–91f, 116f–123f, 156f, 158f, 160f, 162, 162f decussation of, 35f–37f, 45f–46f, 77f, 118f–123f Superior cistern, 74f, 76f, 187f, 189f, 191f, 197f, 199f, 213f Superior colliculus, 12f–13f, 16f–17f, 20f–21f, 31, 35f–37f, 46f–47f, 77f, 94f–97f, 116f–121f, 199f, 203f brachium of, 20f–21f, 47f, 75f, 96f–97f, 114f–115f, 143f Superior frontal gyrus, 6f–9f, 12f–15f, 50f–51f, 60f, 62f, 194f–197f, 201f, 203f Superior oblique nerve (CN IV), 144 Superior olivary nucleus, 43f, 138, 138f Superior parietal lobule, 4f–7f, 202f–203f Superior peduncle, 158 Superior rectus nerve (CN III), 144 Superior sagittal sinus, 191f, 193f–197f, 199f–201f, 203f–205f Superior temporal gyrus, 6f–11f, 18f–19f, 50f–51f, 60f, 62f, 64f, 66f, 68f, 70f, 72f, 74f, 86f–91f, 138, 195f–196f, 200f Superior vestibular nucleus, 41f–43f, 86f–87f, 140f Supplementary motor area, 164f Supplementary motor cortex, 128–132, 146–150 Suprachiasmatic nucleus, 170 Supramarginal gyrus, 6f–9f, 50f–51f, 197f, 200f–202f Supraoptic nucleus, 171–172, 171f Sympathetic preganglionic neurons, 24f–25f T Taste buds, 132–134 Temporal bone, 187f, 190f Temporal lobe, 2f–3f, 188f, 194f, 198f, 204f, 211f Temporalis, 188f Tentorium cerebelli, 1 Terminal (thalamostriate) vein, 63f, 65f, 67f, 69f, 71f, 73f, 75f, 94f–101f, 114f–117f, 173f, 209f Thalamic association nuclei, 166f–167f Thalamic fasciculus, 67f, 152, 152f, 164f Thalamic neurons, 169f Thalamic nuclei, 128f, 174–178 Thalamic relay nuclei, 164f–165f Thalamic reticular nucleus, 63f Thalamostriate vein. see Terminal (thalamostriate) vein Thalamus, 4f–5f, 53f, 62f, 64f, 66f, 68f, 70f, 72f, 74f, 76f, 79f, 103f, 112f–123f, 150f, 154f, 160f, 168–170, 168f, 173f–174f, 176f, 178f, 180, 184–186, 184f–185f, 189f, 191f, 195f–197f, 200f, 203f anterior, 64f external medullary lamina, 94f–101f, 112f–115f location of, 211f, 213f medial geniculate, 35f–37f, 47f

278

Index

Thalamus (Continued) nuclei of anterior, 96f–101f, 116f–121f centromedian, 94f–99f, 114f–117f dorsomedial, 94f–101f, 116f–123f lateral dorsal, 100f–101f, 114f–117f lateral geniculate, 94f–95f, 112f–113f, 196f lateral posterior, 100f–101f, 112f–115f medial geniculate, 94f–95f, 114f–115f, 199f midline, 122f–123f parafascicular, 94f–95f, 116f–119f pulvinar, 96f–101f, 112f–121f reticular, 94f–101f, 112f–115f ventral anterior, 94f–99f, 114f–119f ventral lateral, 96f–101f, 114f–117f ventral posterolateral, 94f–99f, 112f–115f ventral posteromedial, 94f–97f, 114f–115f posterior third of, 70f reconstructions of, 49f–51f, 103f stria medullaris of, 14f–15f Third ventricle, 53f, 64f, 66f, 68f, 70f, 79f, 88f–99f, 120f–123f, 188f–189f, 191f, 195f–196f, 199f–200f, 211f infundibular recess, 86f–87f infundibular recess of, 122f–123f optic recess of, 120f–123f pineal recess of, 122f–123f reconstruction of, 103f root of, 100f–101f suprapineal recess of, 122f–123f Third ventricle, reconstructions of, 50f–51f Thoracic segment, spinal cord, 28f Three-dimensional reconstructions, 49 Tomography, 187 Tongue, 203f Tonsil, 155f–156f Transverse fibers, 158f Transverse fissure, 6f–7f, 10f–11f, 18f–19f, 64f, 66f, 68f, 70f, 72f, 88f–101f, 189f Transverse pontine, 42f Transverse sinus, 187f, 197f–198f, 202f, 208f–209f, 213f Transverse temporal (Heschl’s) gyri, 138–140, 139f, 196f, 202f Trapezoid body, 35f–37f, 42f–43f, 116f–123f, 138, 138f Trigeminal endings, 132–134 Trigeminal ganglion, 126, 126f, 128f, 132, 132f Trigeminal ganglion cells, 128 Trigeminal motor nucleus, 128–132, 132f, 145f–146f

Trigeminal nerve (CN V), 2f–3f, 10f–11f, 20f–21f, 35f–37f, 43f, 128–132, 132f–133f, 145–150, 146f motor root, 10f–11f motor root of, 145f sensory root, 10f–11f Trigeminal nerve fibers, 86f–87f Trigeminal nucleus, 35f–37f, 114f–115f main sensory nucleus, 35f–37f, 43f, 86f–87f, 114f–115f mesencephalic nucleus, 43f–44f motor nucleus, 43f, 86f–87f Trigeminal projections, 164f Trigeminal tracts, 35f–37f mesencephalic tract, 43f–44f Trigeminocerebellar neurons, 132 Trochlear decussation, 118f–123f Trochlear nerve (CN IV), 10f–11f, 20f–21f, 44f–45f, 140–144, 144f Trochlear nucleus, 35f–37f, 45f, 120f–121f, 144f Tuber cinereum, 10f–11f, 122f–123f U Uncinate fasciculus, 162–168, 162f Uncus, 4f–5f, 10f–15f, 18f–19f, 86f–87f, 114f–115f, 172–178, 188f Upper quadrants, in lower bank, 142f Utricle, 138–140 V Vagal trigone, 20f–21f Vagus, dorsal motor nucleus of, 148f Vagus nerve (CN X), 10f–11f, 18f–21f, 39f, 134, 134f, 145–150, 145f–146f Vascular amyloid, Alzheimer disease in, 230f–231f Vasopressin, 171–172 Venous angle, 191f, 209f Venous outflow, 171f Ventral amygdalofugal pathway, 65f, 88f–91f, 112f–113f, 170–171, 173–174 Ventral “amygdalofugal” pathway, 173f–174f, 174–178, 176f Ventral anterior nucleus, 152–153, 153f, 168f Ventral cochlear nuclei, 136–138, 138f Ventral lateral nucleus, 65f, 67f, 69f, 71f, 152–153, 152f–153f, 160, 168f Ventral pallidum, 63f Ventral posterolateral nucleus (VPL), 67f, 69f, 71f, 126–128, 126f, 128f, 168f

Ventral posteromedial nucleus (VPM), 69f, 71f, 126, 126f, 128, 128f, 132, 132f, 134, 168f Ventral root, 2f–3f, 130f C1, 2f–3f, 18f–19f C2, 2f–3f, 18f–19f C4, 2f–3f C5, 2f–3f C6, 2f–3f C8, 2f–3f Ventral root fibers, 26f, 28f–30f Ventral striatum, 150–151, 153–154, 170f, 174–178, 180, 184 Ventral tegmental area, 35f–37f, 46f–47f, 73f, 75f, 153–154, 153f, 183–184, 184f Ventricles, in Alzheimer disease, 230f–231f Ventricular system ependymoma in, 221f meningioma in, 224f–225f Vermis, 140. see also Cerebellum Vertebral artery (VA), 2f–3f, 10f–11f, 116f–119f, 190f, 198f, 203f, 210f–211f areas supplied by, 33f, 116f–123f Vertebral nerve, 2f–3f Vestibular division, of cranial nerve VIII, 138–140, 140f Vestibular ganglion, 138–140 Vestibular nucleus, 40f–43f, 116f–119f, 138–140, 158–160, 158f, 162–168, 162f Vestibular schwannoma (magnetic resonance image of), 204f Vestibular system, 140f–141f Vestibulocochlear nerve (CN VIII), 10f–11f, 18f–21f cochlear division of, 136–138, 138f vestibular division of, 138–140, 140f Vestibuloocular reflex, 140 Visceral afferents, 148f–149f, 170 Visual cortex, 143f, 164f, 168f, 176f, 200f stripe of Gennari, 112f–117f Visual field, of right eye, 142f Visual pathway, 142f Visual system, 142f Vitreous, 188f, 190f, 199f, 202f W White matter, 24f–25f, 157f, 193f, 204f Z Zona incerta, 67f, 114f–115f

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