Human Brain Anatomy in Computerized Images - Hanna Damasio

Human Brain Anatomy IN COMPUTERIZED

IMAGES

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Human Brain Anatomy IN

COMPUTERIZED IMAGES

HANNA DAMASIO, M.D. Professor of Neurology and Director of the Human Neuroanatomy and Neuroimaging Laboratory at the Department of Neurology University of Iowa College of Medicine

OXPORD UNIVERSITY PRESS

2005

SECOND EDITION

OXFORD UNIVERSITY PRESS Oxford University Press, Inc., publishes works that further Oxford University's objective of excellence in research, scholarship, and education. Oxford New York Auckland Cape Town Dar es Salaam Hong Kong Karachi Kuala Lumpur Madrid Melbourne Mexico City Nairobi New Delhi Shanghai Taipei Toronto With offices in Argentina Austria Brazil Chile Czech Republic France Greece Guatemala Hungary Italy Japan Poland Portugal Singapore South Korea Switzerland Thailand Turkey Ukraine Vietnam

Copyright © 1995, 2005 by Oxford University Press, Inc. Published by Oxford University Press, Inc. 198 Madison Avenue, New York, New York 10016 www.oup.com Oxford is a registered trademark of Oxford University Press All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior permission of Oxford University Press. Library of Congress Cataloging-in-Publication Data Damasio, Hanna. Human brain anatomy in computerized images / Hanna Damasio.—2nd ed. p. ; cm. Includes bibliographical references and index. ISBN-13 978-0-19-516561-6 ISBN 0-19-516561-6 1. Brain—Tomography—Atlases. 2. Brain—Magnetic resonance imaging—Atlases. I. Title. [DNLM: 1. Brain—anatomy & histology—Atlases. 2. Image Interpretation, Computer-Assisted—Atlases. 3. Magnetic Resonance Imaging—Atlases. WL 17 D155h 2005] QM455.D23 2005 611'.81—dc22 2004053157 987654321 Printed in China on acid-free paper

To Antonio


Preface

T

his is the second and entirely revised edition of Human Brain Anatomy in Computerized Images. The principal aim of the book remains unchanged: to assist clinicians and researchers in the analysis of human neuroanatomic images obtained with computerized tomographic techniques and to serve as a tool for teaching neuroanatomy. The organization of the second edition is similar to that of the first, but all the images are new and come from new brain specimens. The book begins, in Chapters 2-4, with a description of the external anatomy of the brains used in Chapters 7-9 to depict the different sets of axial and coronal slices. The three main specimens are a dolichocephalic brain, the brachicephalic brain of a person of Caucasian descent, and the brain of a person of Asian descent, which allowed me to include an extreme brachicephalic example. These brains are shown in the same views as in the first edition, and their sulci and gyri are identified. A collection of 26 new normal brains follows the first three, shown from several views—lateral, mesial, top, and bottom—with the major sulci identified. Half are from men and half are from women; gender, age, and handedness are noted for all. The chapters depicting axial and coronal slices obtained from the first three brains include a larger number of slices than in the first edition because the slice interspace was reduced to 5 mm, to provide greater detail. Also, each magnetic resonance slice was stripped of all non-brain structures to facilitate the labeling of anatomic details. The original magnetic resonance images for each slice are posted in the upper and lower corners of the page. At the beginning of each section, I added an image of the brain with colored gyri and a grid depicting the position of slices. A small black-and-white image showing the appropriate slice position also has been added to each page with axial or coronal slices. Sequences of axial slices parallel to the canto-meatal line, at a rostral tilt of —30° and a caudal tilt of +10°, are shown for all three brains, as are the coronal slices for the first two axial sequences. A parasagittal

[vii]

Preface

sequence is shown for the first brain, and Brodmann's cytoarchitectonic fields are shown in an axial sequence. A new chapter was added to address issues of brain structure quantification. A final chapter, providing examples of lesioned brains seen in varied incidences of cut, fulfills the same role as in the first edition but is based on new cases. Iowa City, Iowa

[viii]

H.D.

Acknowledgments

I

would like to thank all the colleagues who commented on the first edition of this book and encouraged me to prepare a better second edition. I would also like to thank Jeff House and Fiona Stevens at Oxford University Press, respectively, the editors of the first and second editions, for their steady support and guidance. I am grateful to Joel Bruss, who assisted me in the preparation of many images, collaborated with John Allen and me in Chapter 6, and helped me with the index and the rechecking of the final images. He also prepared the images used in the dust jacket. I will not forget his good will and good humor. I am equally grateful to Jon Spradling, who, as always, assisted me in virtually all aspects of image processing with his usual patience and expertise. I also acknowledge Sonya Mehta, who was always ready to answer questions regarding the use of graphics programs; Jocelyn Cole, who traced all the brain specimens used in the book; Keary Saul and Julie Sexton, who assisted me in the preparation of the final manuscript; and my assistant Neal Purdum, who facilitated communication with the editors and solved all sorts of last-minute problems. I thank all of them deeply for their professionalism and good will. Finally, I cannot thank Antonio Damasio enough for putting up with all the hours I spent glued to the computer.

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Contents

List of Structures Identified in the Figures and Their Abbreviations 1 Introduction

xiii

1

2 Exterior Description of a Normal Dolichocephalic Brain 11 Sulci • Gyri • Brodmann's fields 3 Exterior Description of a Brachicephalic Brain 31 Sulci • Gyri 4 Exterior Description of Another Brachicephalic Brain 39 Sulci • Gyri 5 An Alphabet of Normal Brains 47 6 Quantifying Neuroanatomic Differences 77 In collaboration with John S. Allen and Joel Bruss 7 Sections through Dolicho 97 Canto-meatal incidence: axial slices 100 Canto-meatal incidence: coronal slices 126 Hyperextension incidence: axial slices 160 Hyperextension incidence: coronal slices 188 Posterior fossa incidence: axial slices 222 Parasagittal incidence 248 Brodmann's fields 286 8 Sections through Brachi-1 293 Canto-meatal incidence: axial slices 294

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Contents

Canto-meatal incidence: coronal slices 320 Hyperextension incidence: axial slices 352 Hyperextension incidence: coronal slices 378 Posterior fossa incidence: axial slices 408 9 Sections through Brachi-2 435 Canto-meatal incidence: axial slices 436 Hyperextension incidence: axial slices 462 Posterior fossa incidence: axial slices 488 10 Application to Lesion Studies 515 A left parietal lesion 517 A left calcarine lesion 521 A right temporal lesion 525 A left frontal lesion (subcortical) 529 References 533 Index of Anatomical Structures Seen in the Figures

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537

List of Structures Identified in the Images and Their Abbreviations

Sulci

anterior insular sulci anterior occipital sulcus ascending branch of sylvian fissure ascending ramus of cingulate sulcus calcarine fissure central sulcus cingulate sulcus circular sulcus collateral sulcus frontomarginal sulcus H-shaped sulci hippocampal fissure horizontal branch of sylvian fissure inferior frontal sulcus inferior temporal sulcus intraparietal sulcus lateral occipital sulcus lateral orbital sulcus lateral temporo-occipital sulcus lingual sulcus middle frontal sulcus midfrontal sulcus midorbital sulcus occipitoparietal sulcus olfactory sulcus paracentral sulcus postcentral sulcus

ants AOS abSF arCingS CalcF CS CingS CircS,* ColS FmS HsS HipF hbSF IPS ITS IPS LOS LatOrbS LTOS LingS MFS mFS mOrbS OPS OlfS paraCS postCS

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posterior insular sulci precentral sulcus rhinal sulcus suborbital sulcus subparietal sulcus superior frontal sulcus superior temporal sulcus inferior ramus superior ramus sylvian fissure temporo-occipital sulcus transverse occipital sulcus transverse temporal sulcus

posts preCS RhS, rhS sOrbS sPS SFS STS STSir STSsr SF TOS trOS, trsOS trTS

Gyri, central structures, cerebellum, and brain stem amygdala anterior commissure caudate nucleus body of caudate nucleus head of caudate nucleus tail of caudate nucleus cerebellum cerebellar hemispheres cerebellar tonsils cerebellar vermis cingulate gyrus claustrum colliculi inferior superior corpus callosum beak splenium cuneus fornix frontal lobe frontal pole fusiform gyrus gyrus rectus Heschl's gyrus hippocampus hypothalamus inferior frontal gyrus pars opercularis pars orbitalis

[xiv]

a ac c be he tc cereb cerebH cerebT cerebV CingG 3 ic sc CC bCC, bcc sCC, sec Gun for FL FP FusiG Grec HG hip ht IFG IFG, po IFG, porb

pars triangularis inferior parietal lobule angular gyrus supramarginal gyrus inferior temporal gyrus insula anterior posterior internal capsule anterior posterior lateral occipital gyri lingual gyrus mamillary body medulla mesencephalon middle frontal gyrus middle temporal gyrus occipital pole orbital frontal gyri anterior orbital gyrus lateral orbital gyrus middle orbital gyrus posterior orbital gyrus pallidum paracentral gyrus parahippocampal gyrus parietal lobe planum temporale pons postcentral gyrus posterior commissure precentral gyrus precuneus putamen quadrigeminal plate retrosplenial area spinal cord superior frontal gyrus superior parietal lobule superior temporal gyrus temporal lobe temporal pole temporo-occipital gyrus thalamus

IFG, pt IPL AG SMG ITG Ins 1 2


aic pic LOG LingG mb med mes MFC MTG OP OrbG aOrbG lOrbG mOrbG pOrbG pa paraCG paHG PL PT pons postCG

pc preCG, preCg preCun pu qpl rSp sc SFG SPL STG TL TP TOG th

[xv]


Human Brain Anatomy IN COMPUTERIZED

IMAGES


Chapter 1 Introduction

T

his is a completely revised edition of an atlas designed with two goals in mind: the first is to assist clinicians and researchers in analyzing human neuroanatomic images obtained with computerized tomographic techniques; the second is to serve as a tool for teaching neuroanatomy to the students who are becoming acquainted with anatomic data either at the computer screen or by means of radiologic transparencies rather than through the study of postmortem specimens. The images in the atlas depict the structures of the telencephalon (cerebral cortex, basal ganglia, and thalamus) and cerebellum, but the focus is on the cerebral cortex. The refinement of imaging technologies such as X-ray computerized tomography and magnetic resonance (CT and MR) has given neuroscientists and clinicians concerned with brain function and brain diseases access to the macroscopic neuroanatomy and neuropathology of living humans. The amount of structural information these technologies make available is remarkable, and both research and clinical practice are inconceivable today without their support. Yet proper interpretation of the information contained in tomographic scans is a difficult task, and if the purpose of the interpretation is to produce a fine neuroanatomic description, the reliability of the result is often problematic. There are several reasons behind these difficulties. One has to do with the fact that, more often than not, the imaging sections generated by a scanner are different from the idealized brain sections we have committed to memory or can find in standard brain atlases. The difficulty is compounded by the fact that superficially the imaging sections resemble the standard brain sections and the observer can be more easily misled. In brief, the axial incidence of section according to which most modern scans are obtained is not the same as in standard atlases and can vary from scan to scan. If this reservation applies to axial incidences, it applies even more strongly to coronal incidences because they are, by convention, obtained at 90° angles from the axial incidence chosen for a given person. Thus, coronal incidences vary from study to study as much as axial incidences do.

[1]

Human Brain Anatomy IN COMPUTERIZED IMAGES

[2]

One may well ask why incidences vary so much. The answer is that variation is unavoidable for diverse reasons: the design of the head (an incidence parallel to the canto-meatal line is quite different in a dolichocephalic head and in a brachicephalic head, as shown in the first sequence of Chapter 7 and of Chapters 8 and 9), the mobility of the spine and neck (older persons with stiffer necks often lie on the scanning table with hyperextended heads and end up being scanned in these incidences; examples of such an incidence are shown in the second axial sequence of Chapters 7-9), and the need to select a special plane to target the region where a lesion is presumably located (as in a posterior fossa incidence required to better visualize the cerebellum and brain stem, shown in the third axial sequence in any of Chapters 7-9). Furthermore, incidences are chosen in relation to external landmarks, most often the cantomeatal line. Unfortunately, the relation of the canto-meatal line to brain structures is not consistent from subject to subject, as can be seen in Figure 1-1. For practical purposes then, tomographic brain sections come in a wide range of incidences, few of which match the textbook image of brain sections available in traditional brain atlases. This reduces the "fit" between the section to be interpreted and the section kept in our mind or in the library atlas. The chance of a poor fit is further increased by the sheer ambiguity of the anatomic features depicted in cross-section—one sulcus looks like any other sulcus when you see its section in a two-dimensional (2-D) thin slice—and by the very real difficulty of mentally transforming 2-D surfaces into 3-D volumes. Be that as it may, this is how anatomic localization must be carried out: by taking a 2-D section and mentally picturing its position as a component of the 3-D volume where it belongs or by acquiring MR images with the purpose of creating 3-D reconstructions of the brain and proceeding with direct observation and identification of sulci and gyri in that unique brain. In brief, images that correspond closely to the sections obtained in routine imaging procedures are not easy to find in standard atlases. The problems posed by the variation of scanning incidence are made worse by an often neglected biologic reality: individual anatomic variation. When one considers the anatomy of the human brain across a large number of individuals, one is struck both by the similarity and by the uniqueness of its macroscopic features. The similarity is easy to appreciate: we do find the same major components in each and every specimen. All normal brains have a brain stem, a cerebellum, and two hemispheres; and each hemisphere can be subdivided into four lobes (frontal, parietal, occipital, and temporal), which maintain their relative positions. Moreover, as we look at the lateral surface of every brain, we can find two prominent sulci, the central sulcus and the sylvian fissure; and every mesial brain surface shows us a similarly placed corpus callosum. The similarity ends here, however. Using plain, naked-eye analysis, we can appreciate that from one individual to the next even the central sulcus and sylvian fissure travel in different courses and that, even within the same individual, there are clear differences between the two hemispheres (see Fig. 1-2). When we analyze the secondary sulci within each lobe, the differences between individuals and between the two hemispheres of the same individual become even more pronounced. Chapters 2-5 amply demonstrate this point.

In neuroanatomy, then, there is a permanent tension between similarity and singularity, between anatomic constants and individual variation. This tension is not a mere curiosity. It has many practical implications. Neuroscientists studying normal populations or using the lesion method must take into account similarity and singularity. Likewise, neurologists and neurosurgeons must determine not only the pathologic nature of lesions but also where they are with precision, especially when they need to plan an optimal surgical approach or predict future deficits and improvements. Finally, it is important to make medical students and graduate students aware of anatomic uniqueness because they must learn to deal with its consequences in both clinical practice and research. The issue of anatomic uniqueness has gained importance because of the spectacular developments in neuroimaging technologies. As recently as the 1970s, researchers and clinicians used to make guesses and attempted to assess the merit of those guesses by descending surgically on the living brain, scalpel in hand, or by studying the real thing at the autopsy table. Images from CT and MR have changed this situation radically. In particular, MR provides such faithful anatomic details at such fine resolution that it has permitted the emergence of a new field: human neuroanatomy in vivo. The only way of eliminating the problems posed by individual anatomic variation is to obtain a 3-D brain reconstruction for every subject and to use it for a customized analysis of the individual's anatomy. In the many circumstances in which a 3-D reconstruction is either not possible or practical, however, errors of interpretation can be minimized by becoming familiar with common profiles of variation in key neuroanatomic structures. That is something I hope to help readers achieve. This book provides a collection of normal human brains in 3-D reconstruction (labeled A-Z), which demonstrates a wide range of anatomic variation. It also provides a comprehensive collection of 174 sections obtained in a single, dolichocephalic brain, using six different incidences of cut, to guarantee that the same structure identified in the section of one incidence is also present in the section from another incidence that intersects it. This reveals unequivocally the degree to which different types of incidence alter the appearance of the same anatomic structure. Moreover, axial and coronal sections are also included at the same incidences in two other brains, of brachicephalic configuration, chosen for having about as different an overall shape as the "standard" brain used in the first collection. The illustrations of feature variation as well as this latter set of sections are meant to ease problems of interpretation by providing examples of brain sections obtained axially and coronally at the most frequently used incidences of cut. As a whole, they also will help the reader develop a sense of the "correction" that must be applied to the images of some individuals in whom the typical structures do not fit the standard image. The atlas is based on a technique developed in my laboratory, known as Brainvox (Damasio and Frank, 1992; Frank et al., 1997). It allows for the reconstruction of the brain in three dimensions, at a level of detail compatible with identifying all major sulci and gyri with the same degree of precision

Introduction

[3]


[4]

achievable at the autopsy table. Moreover, once identified, the sulci can be traced on the 3-D image and the outline of the tracings can be transferred automatically to the original 2-D images. Because the 3-D reconstruction obtained with Brainvox is not a surface rendering but a voxel rendering, the image of a 3-D volume can be cut in any spatial plane; for example, axial, coronal, parasagittal, oblique, and the color-coded sulci tracings from the 3-D image can be carried onto the new cut, thus maintaining sulci identification. In fact, we can go further than we would at autopsy because we are not limited to one plane of cut; we are free to cut and recut as necessary. Any sulcus or gyms seen in a 2-D slice can be interrogated and studied in the 3-D image, automatically bypassing any "guessing" process. Brainvox has been used extensively in the study of patients with focal brain lesions (a few examples of such lesions are given in Chapter 10). The technique has also been used in the preparation of neurosurgical interventions by providing high-quality anatomic images of a particular brain rendered in 3-D, with the sulci identified and marked. It is a helpful tool in the stereotactically guided implantation of intracerebral electrodes, and it allows for checking of the location of such electrodes after implantation. Brainvox also has been used to study the detailed anatomy of the brains of apes. Erroneous beliefs regarding the comparative anatomy of the frontal lobe in humans and apes have been rectified on the basis of Brainvox data (Semendeferi and Damasio, 2000; Semendeferi et al., 1997). Figure 1-3 shows an example of each extant ape's brain and permits comparison with a human brain and with the brain of a macaque. (The mean volume and proportional values given in the figure come from Semendeferi and Damasio, 2000, and, for the macaque, from Semendeferi et al., 1997.) Chapter 2 shows a variety of views of a normal dolichocephalic brain from a fully right-handed Caucasian man, 47 years of age, a brain different from that shown in the first edition. The sulci are identified in one set of images and the gyri in another. The complete names of the different anatomic structures, followed by the respective abbreviations used in the plates, are provided in a single table. The chapter also includes a set of images with the markings of Brodmann's cytoarchitectonic regions (Brodmann 1909; 1999) superimposed on the gyri. Chapter 3 depicts another normal brain, with a different overall configuration. For this chapter, I selected the brachicephalic brain of a Caucasian woman, also fully right-handed, 43 years of age. This brain too is different from the brachicephalic example of the first edition. It helps illustrate, in Chapter 8, how the same slice incidence can appear so different in a brain of different overall shape. Chapter 4 shows another brachicephalic brain, that of a 34-year-old, fully right-handed man of Asian descent. I added this example to show how the slice incidences shown in Chapters 7 and 8 have a very different appearance in a shorter and wider brain. (The slices through this brain are shown in Chapter 9.) Chapter 5 presents a series of 26 normal brains, labeled A-Z. These brains are presented in 3-D reconstruction and are seen from the left and right lateral aspects, from the two mesial surfaces, as well as from above and below. This

series, also different from the one presented in the first edition, allows the reader to appreciate better the variability of sulci and gyri and to see how it accounts both for right-left differences and for differences among individuals. The brains in Chapter 5 are organized in five groups. The chapter begins with the brains of eight young, fully right-handed subjects, followed by a group of four strongly left-handed subjects and another of six subjects with mixed handedness. Next, there is a pair of right-handed identical twins, followed by six older fully right-handed subjects. The brains come from 12 women and 12 men; the two identical twins are female. The woman's brain is always on the right; the matching man's brain is depicted on the left. Age, gender, and handedness scores are provided for each case. Chapter 6 is new and deals with quantitative analyses. It was prepared in collaboration with John Allen and Joel Bruss. The chapter provides numerical results obtained in the segmentation of large numbers of normal brains into different lobes. It also depicts a collection of 46 brains, half male and half female, in which the different lobes were segmented and color-coded, together with tables for the sizes of the segmented volumes. Chapter 7 shows three different axial sequences and the corresponding coronal sequences for two of them as well as one set of parasagittal slices. All come from the dolichocephalic brain described in Chapter 2. The sulci are indicated in the images on the left and the gyri, in those on the right. For this second edition, I chose smaller spacing of the slices, only 5 mm apart, and marked the sulci and gyri on slices in which all nonbrain structures were removed, to increase the clarity of the image. However, the "radiologic image," with the nonbrain structures in place, is visible in the upper and lower corners of each page, along with a marking of the position of the cut as seen on the right and left hemispheres, in both lateral and mesial views. Chapter 8 shows the first brachicephalic brain (described in Chapter 3) in the three axial and the two coronal incidences of Chapter 7. Chapter 9 shows the second brachicephalic brain (described in Chapter 4) in the same three axial incidences. Chapter 10 provides examples of lesions seen in 3-D reconstruction and in varied incidences of cuts. All images in this second edition are new and were obtained in a General Electric Signa scanner operating at 1.5 Tesla, using the following protocol: SPGR/50, TR 24, TE 7, 1 NEX matrix 256 X 192, FOV 24 cm. For each brain, three separate MR sequences with 1.5-1.6 mm contiguous coronal slices were obtained and averaged post hoc using the Automated Image Registration (AIR 3.03, UCLA; Woods et al., 1992), to improve resolution. The final 3-D volume was obtained with Brainvox, which was also used to reslice the first three brains and obtain the different sets of images. Adobe Photoshop and Adobe Illustrator programs were used subsequently to label the images and smoothen the peripheries, but I did not attempt to eliminate all pixellation. My priority was to produce images that would reflect what is seen in high-quality MR scans rather than to artificially smooth out images for esthetic purposes. All brain sections are shown according to radiologic conven-

Introduction

[5]


[6]

tion, the right hemisphere appearing on the left and the left hemisphere, on the right. All brains come from the patient and normal subject registries of the Division of Cognitive Neuroscience at the University of Iowa. All scans were obtained with informed consent, in accordance with institutional and federal guidelines.

Figure 1-1

Transparent heads showing the left hemisphere of the brains described in Chapters 2-4. The canto-meatal line is shown in red. A few slices parallel to the canto-meatal line are shown to exemplify how a plane set on the basis of external landmarks

intersects different brain regions in heads of different configuration. Top: The dolichocephalic brain shown in Chapter 2. Bottom: The two brachicephalic brains shown in Chapters 3 and 4, respectively.

[7]

Figure 1-2

Top: Sulci of the three brains discussed in Chapters 2-4 superimposed on the image of an averaged brain (based on 50 normal brains) after each of the three brains was morphed to the averaged brain (using Woods et al., 1999 Average Image Registration). Note how the sulci remain individualized and at times

quite far from their counterpart in the other brains. Bottom: Results of the same process applied to the two identical twin brains shown in Chapter 5 (brains S and T). Note that the superposition of sulci is better for the twins than for the three brains in the top image. Still, the superposition is not perfect.

.human cerebrum FL TL _ErOL

insula

bonobo

cerebrum FL TL p-OL insula

volume in cc_% of cerebrum

_ 290.5 101.5 48.2 109.1 3,7

_

_ 34.9 16.6 37.6 1.3

chimpanzee volumeincc Hofcerebrum

cerebrum FL

_TL.

P-OL insula

gorilla cerebrum FL_ TL P-OL insula

279,7 97.2 48.2_ 103.6 3,1

34.8 17.2 37.0 1.1

volumeinct %ofcerebrum 355.9 124.8 35.1 49.8 14.0 142.6 ' 39.9 5.3 1.4

Figure 1-3 I lunian and e\uni ape brains \viih the niiiior lobes Lokii'-Loded. L'tiiler i-Mi.li brain are 1 tbe mean valut;.^ lor iib.solnie brain •.i/e and lur iliL1 perLenia^e oeijupied bv eaeli lobe (as reported in Seniendek-fi and I J.iiiiasiu, 2000; Semendefcri el al., 19971. Note

volume in cc % of cerebrum

1233.8_ 454.8 223.2 448.8_ 17.4

36,8 18.1 36,4 _ 1.4

orangutan

volume in cc % of cerebrum

cerebrum _EL

_P-OL insula

gibbon

_

391.2 142.3 65.7_ 138.8 4,8

36.3

16.8_ 35.5 1.2

volumeincc %ofcerebrum

71.6 203

cerebrum FL TL P-OL insula

13.5 28.1 0.7

rhesus

cerebrum

28.4 18.9 39.2 1.0

volume in cc

62.7

llic marked dille'renee in absoluie si/e and the remarkable similarity ol lira in lobe proporlions among the human ,ind ape tir.it us. Mrains Lire shown in their approximate size reladon.

[9]


Chapter 2 Exterior Description of a Normal Dolichocephalic Brain

T

he brain chosen for this chapter is a typical dolichocephalic brain of a fully right-handed, 47-year-old man. It conforms to the most commonly depicted global brain image, what one might call a "standard" brain. I have called it Dolicho. This brain is shown first from the lateral view (Figs. 2-1, 2-2), then from the mesial view (Figs. 2-3, 2-4). Both hemispheres are seen together, the left on the upper tier and the right on the lower tier, to allow an easy right-left comparison of the different structures. For each hemisphere, a straight lateral or mesial view is shown together with a downward tilt for the lateral view and an upward tilt for the mesial view. In the latter image, the cerebellum and brain stem have been removed to allow complete inspection of the mesio-inferior temporal lobe. It is important to realize how asymmetric the sulci are. The asymmetry between the right and left hemispheres is certainly not limited to the sylvian fissure, the one structure traditionally considered asymmetric. By comparing the image on the left, showing the sulci (Figs. 2-1, 2-3, 2-5), with the image on the right, showing the gyri (Figs. 2-2, 2-4, 2-6), on each set of two facing pages, the reader can easily see which sulci provide the limits for each of the gyri. These images are followed in the upper tier by a view from the top and a view of the inferior surface of the brain (the cerebellum was removed in the latter view to permit observation of the inferior surface of the temporal and occipital lobes) and in the lower tier by images showing the frontal and occipital perspectives (Figs. 2-5,2-6). These images are followed by the same views of the brain seen in Figures 2-2, 2-4, and 2-6 but with the approximate limits of Brodmann's cytoarchitectonic fields superimposed on the colored gyri (Figs. 2-7, 2-8, 2-9). The chapter closes with two images showing hidden structures: Figure 2-10 shows the superior aspect of the superior temporal gyrus after removal of the frontal and parietal lobes, and Figures 2-11 and 2-12 show the insula after removal of the overlaying frontoparietal operculum and upper portion of the superior temporal gyrus.

[11]


[12]

When one looks at lateral views of the brain, two major sulci should be identified: (1) the central sulcus (CS), which separates the frontal from the parietal lobe, and (2) the sylvian fissure (SF), which separates those two lobes from the temporal (Figs. 2-1, 2-2). The central sulcus is often a continuous valley with an antero-inferior course descending from the interhemispheric fissure toward the sylvian fissure. It usually does not reach the sylvian fissure (as in Dolicho and Brachi-1), but it may do so, as in Brain-A, the left hemisphere of Brachi-2, the right hemisphere of Brain-K, and the left hemisphere of Brain-V. The lower end of the sulcus continues in its main direction or makes a backward kink (compare Brain-A and -B for an example). The sylvian fissure adopts an anteroposterior and mostly horizontal course, especially in the left hemisphere, where it is usually longer. The anterior end of the sylvian fissure branches into two rami, which course in the frontal lobe. These are known as the ascending (abSF) and the horizontal (hbSF) branches of the sylvian fissure. The rami may constitute two independent sulci with a common origin, as in the left hemisphere of the present brain, or have a common trunk and then separate into individual branches, as in the right hemisphere. The sylvian fissure has a horizontal and long course in the left hemisphere and terminates in this fashion (as in this brain and in Brain-F, -N, and -O), or it may terminate by turning down at the end (as in Brain-D, -L, and -Z). It may also split in two small branches as seen in Brachi-2 and Brain-M. In the right hemisphere, however, it tends to have a shorter horizontal course, after which it turns upward at the end (as in the present brain, Brachi-2, and most of the brains shown in Chapter 5). The description above conforms to the classical concept we have of the right and left SF in right-handed subjects. However, as we will see in Chapter 5, there are exceptions (see, e.g., Brain-G, that of a fully right-handed subject). In BrainG, there is a complete reversal of the course of the SF. It is the right SF that turns sharply down at its end and the left that shows an upward course. See also Chapter 6 for both types of presentation. There are two sulci parallel to the central sulcus. Anteriorly, the precentral sulcus (preCS) most often shows two separate segments, as in Brachi-1 (also Brain-E, -J, -S, and -T). Together with the central sulcus, the precentral sulcus defines the precentral gyrus (preCG). In its posterior and superior sector, the precentral gyrus contains Brodmann's field 4, which continues in the depth of the central sulcus in its inferior segment. It corresponds to the primary motor cortex. The anterior and inferior two-thirds of the precentral gyrus contain Brodmann's field 6, which corresponds to the premotor cortex. (For cytoarchitectonic markings, see Figs. 2-7, 2-8, 2-9.) The postcentral sulcus (postCS) is posterior to the central sulcus and roughly parallel to it. This sulcus can be continuous (as in the right hemisphere of Dolicho; Brachi-1 and -2; Brain-F, -L, and -W; and the left hemisphere of BrainH, -I, and -J) or it may have two or three separate segments (as in the left hemisphere of Dolicho and Brachi-1 and the right hemisphere of Brain-J and -S). Together with the CS, it defines the postcentral gyrus (postCG), which contains Brodmann's fields 3, 1, and 2 (the primary somatosensory cortices).

Two additional sulci should be identified: on the lateral surface of the frontal lobe, the superior frontal sukus (SFS) and the inferior frontal sulcus (IFS). Both course in a postero-anterior direction, beginning at about the precentral sulcus but not necessarily connected to it, and are essentially parallel to each other. The superior frontal sulcus is as often continuous as discontinuous. The best views to examine the SFS are superior and anterior (Figs. 2-5, 2-7). In Dolicho and Brachi-1, the SFS is discontinuous in both hemispheres, but in Brachi-2, it is continuous in the right hemisphere and discontinuous in the left. The SFS constitutes the lateral border of the superior frontal gyrus (SFG). The inferior frontal sulcus is more often than not continuous (as in the left hemispheres of the three main brains in Chapters 2-4), although it can be interrupted (as in the right hemispheres of the same brains). It constitutes the upper limit of the inferior frontal gyrus (IFG) and, together with the superior frontal sulcus, limits the middle frontal gyrus (MFC). The middle and superior frontal gyri share several prefrontal association cortices in Brodmann's fields 9 (anteriorly), 8 (middle), and 6 (posteriorly). This posterior segment is the upper expansion of premotor area 6, which we first noted in the postcentral gyrus. The anterior segment of the middle frontal gyrus has a separate cytoarchitectonic area, Brodmann's field 46, which is also part of the prefrontal sector. The inferior frontal gyrus is almost exclusively occupied by the frontal operculum. The operculum is subdivided by the previously mentioned ascending and horizontal rami of the sylvian fissure. The segment between the precentral sulcus and the ascending ramus constitutes the pars opercularis (IFG, po) and contains Brodmann's field 44, usually regarded as a premotor region, while the sector between the abSF and hbSF constitutes the pars triangularis (IFG, pt). The latter contains Brodmann's field 45, which is regarded as part of the prefrontal sector. This cytoarchitectonic area extends inferiorly into the upper sector of the third and most inferior component of the frontal operculum, the pars orbitalis (IFG, porb). The inferior segment of the pars orbitalis contains the lateral segment of Brodmann's field 47, also part of the prefrontal sector. With respect to the left hemisphere, the combination of fields 44 and 45 is also known as "Broca's area." The very anterior tip of the frontal lobe is the frontal pole (FP). It has no macroscopic limits and is occupied by Brodmann's field 10. We saw that the most anterior gyrus in the parietal lobe was the postcentral gyrus limited by the postcentral sulcus and containing the primary somatosensory cortices. In the superolateral surface of the parietal lobe, another important sulcus must be identified: the intraparietal sulcus (IPS). The IPS has an anteroposterior course beginning at the upper half of the postcentral sulcus. It can be continuous or interrupted and is best seen in superior and posterior views (Figs. 2-5, 2-7). It separates the parietal lobe into two lobules. The first is the superior parietal lobule (SPL), which is occupied by the somatosensory association cortex of Brodmann's field 7. Squeezed in between this field and the superior sector of the primary somatosensory cortices is another somatosensory association cortex, Brodmann's field 5. The second is the inferior parietal lobule (IPL), itself subdivided into two independent gyri, the supramarginal

Normal Dolichocephalic Brain

[13]


[14]

(SMG) anteriorly and the angular (AG) posteriorly. The angular gyrus may be seen as the continuation of the middle temporal gyrus into the parietal lobe and is constituted of multimodal association cortex (Brodmann's field 39), while the supramarginal gyrus sits above the superior temporal gyrus. The latter is also multimodal association cortex and contains Brodmann's field 40. The angular gyrus and the superior parietal lobule are contiguous with the lateral occipital gyri, which in humans are occupied by visual association cortices (Brodmann's fields 19 and 18). There is no sulcal separation between the parietal and the occipital lobe on the lateral surface of the brain. Let us return now to the sylvian fissure and the temporal lobe. Parallel and inferior to the sylvian fissure are two sulci, seen on the lateral surface: the superior temporal (STS) and the inferior temporal (ITS). The superior temporal sulcus can be continuous, as in the three main brains and in most of the brains in Chapter 5, or divided into two or three segments, as in Brain-C and -R. It is usually readily identifiable and forms the lower limit of the superior temporal gyrus (STG), also known as the first temporal gyrus. The lateral aspect of the gyrus is occupied by Brodmann's field 22, an auditory association cortex. The superior surface of the gyrus, hidden by the frontal and parietal opercula and accessible to inspection only when the frontal and parietal lobes are lifted (Figs. 2-10, 3-7, 4-7), is occupied by the transverse temporal gyrus or Heschl's gyrus (HG), which contains the primary auditory cortex (Brodmann's fields 41 and 42) and is limited by the transverse temporal sulci (trTS). Heschl's gyrus is most often a single gyrus, but it can be double or partially divided in two. A double HG is found more often in the right hemisphere. The segment of the superior temporal gyrus posterior to Heschl's gyrus is the planum temporale (PT), and in the left hemisphere it is part of Wernicke's area. The sector anterior to the Heschl's gyrus is the planum polare. Both plana are constituted by auditory association cortex (Brodmann's field 22). The inferior temporal sulcus is more difficult to identify because of its many segments. However, both the left hemisphere of Dolicho and the right hemisphere of Brain-E display a long and continuous inferior temporal sulcus. Together with the superior temporal sulcus the ITS limits the middle temporal gyrus (MTG) or second temporal gyrus, which is occupied by higher-order association cortex in Brodmann's field 21 (anteriorly) and by Brodmann's field 37 (posteriorly). The anterior tip of the temporal lobe constitutes the temporal pole (TP) or field 38; as with the frontal pole, there are no macroscopic anatomic landmarks to demarcate the posterior limit of the polar region. The posterior end of the temporal lobe is found at the temporo-occipital incisura, at which a vertical sulcus, the anterior occipital sulcus (AOS) separates the temporal from the occipital lobe. Continuing into the inferior and mesial surfaces of the temporal lobe (see Figs. 2-2, 2-3, 2-5), we find yet another anteroposterior sulcus: the temporooccipital (TOS), which can be continuous, as in Brain-F, the right hemisphere of Brain -I and -Q, and the left hemisphere of Brain-A, or most often separated into two, three, or even four segments. It marks the mesial limit to the inferior temporal gyrus (ITG) or third temporal gyrus. The lateral limit of this gyrus is the inferior temporal sulcus. This gyrus is occupied by higher-order visual as-

sociation cortex: Brodmann's field 20 anteriorly and the continuation of field 37 posteriorly.


Mesial to the TOS, the most notable sulcus is the collateral (ColS). This sulcus marks the mesial limit of the fourth temporal gyrus, also known as the temporo-occipital gyrus (TOG) or fusiform gyrus of the temporal lobe. As was the case with the previous gyrus, it holds Brodmann's fields 20 and 37. The collateral sulcus also constitutes the lateral limit of the parahippocampal gyrus (paHG), or fifth temporal gyrus, largely occupied by Brodmann's field 28 (the entorhinal cortex). Buried inside the collateral sulcus are some important cytoarchitectonic fields, namely, fields 35 laterally and 36 mesially, which can come to the surface of the posterior segment of the parahippocampal gyrus and all along the mesial edge of the fourth temporal gyrus, respectively. The anterior and mesial sector of the parahippocampal gyrus is occupied by field 34 and the posterior and mesial sector, by field 27. The anteriormost tip of the temporal lobe in both the inferior and mesial views forms the temporal pole (Brodmann's field 38, as mentioned earlier). The collateral sulcus and the temporo-occipital sulcus can continue posteriorly into the occipital lobe and respectively limit the lingual (LingG) and fusiform (FusiG) gyri, which contain early visual association cortex (Brodmann's fields 18 and 19). The calcarine sulcus or calcarine fissure (CalcF) is the most important sulcus in the mesial view of the occipital lobe (Figs. 2-3, 2-4). This sulcus is extremely variable in its course and configuration (see mesial views of brains in Chapter 5). It can be extraordinarily different in the right and left hemispheres of the same individual (as in Dolicho) or fairly similar (as in Brachi-1 and -2). Anteriorly, the calcarine joins another major sulcus that separates the occipital from the parietal lobe, the occipitoparietal sulcus (OPS) and then continues its anterior course. Posteriorly, the CalcF can terminate inside the mesial surface of the hemisphere (see Brain-D) or extend to the pole and even to the outer surface (as in the present case, Fig. 2-5). It can terminate in a single straight line or, more typically, in a T or Y shape (see Brain-F and -T, or the left hemisphere of -H, -K, and -L). The primary visual cortex is mostly buried in the depth of the calcarine sulcus, and it overflows to a variable degree onto the inferior and superior banks of the calcarine region. It corresponds to Brodmann's field 17. Between the calcarine sulcus and the occipitalparieto sulcus rests the cuneus (Cun), occupied by early visual association cortex (part of Brodmann's fields 18 and 19). Apart from the sulci described above, the most notable sulcus in the brain's mesial surface is the cingulate (CingS). It is parallel to the corpus callosum (CC) and to its limiting sulcus, the callosomarginal sulcus. It can be continuous, as in the left hemisphere of Dolicho and the right hemisphere of Brachi-1 and -2, or interrupted, as in one or the other hemisphere of several brains in Chapter 5. It is not unusual to see a double cingulate sulcus, as in the right hemisphere of Dolicho or the left hemisphere of Brachi-1 and -2. The posterior end of the cingulate sulcus bends upward in an anterior concave shape, creating the ascending ramus of the cingulate sulcus (arCingS). Another short sulcus can be found posteriorly to the ascending branch and still parallel to the corpus callosum,

[15]


[16]

the subparietal sulcus (sPS), which is most often separate but can also be continuous with the cingulate sulcus (see Brain-B). The cingulate sulcus and the subparietal sulcus form the superior border of the cingulate gyrus. This is limbic cortex, Brodmann's field 24 in the anterior half and field 23 in the posterior. Further back, in the superior section of the posterior half, there is also Brodmann's field 31 and even further back, in the retrosplenial region (Sp), there are Brodmann's fields 26, 29, and 30. Above the subparietal sulcus and between the parieto-occipital sulcus (posteriorly) and the ascending branch of the cingulate sulcus (anteriorly) lies the mesial parietal region or precuneus (preCun). This is somatosensory association cortex (the continuation of Brodmann's field 7). The most anterior sector contains Brodmann's field 5. Buried anteriorly in the callosomarginal sulcus, we find Brodmann's field 33. The ascending branch of the cingulate sulcus usually terminates just behind the superior and mesial extension of the central sulcus and is the landmark of choice to find the mesial extension of the central sulcus. Just anterior to the central sulcus we usually find a more or less vertical sulcus, the paracentral (paraCS), which arises either as a side branch of the cingulate sulcus, as in Brachi-1 and the left hemisphere of Brachi-2, or as a sulcus descending from the outer edge of the interhemispheric space, as in Dolicho and the right hemisphere of Brachi-2. The region, limited by the paracentral sulcus, cingulate sulcus, and ascending branch of the cingulate sulcus is called the paracentral lobule or paracentral gyrus (paraCG), which is mostly occupied by primary motor cortex or field 4 of Brodmann. The most posterior sector, behind the edge of the central sulcus, is occupied by the extension of the primary somatosensory cortices, Brodmann's fields 3, 1, and 2. Anterior to the paracentral sulcus and limited inferiorly by the cingulate sulcus lies the mesial surface of the superior frontal gyrus. The major cytoarchitectonic component is the large expansion of field 6, premotor cortex, which on the medial surface constitutes the supplementary motor area. Fields 8 and 9 sit just in front. Again, the tip of the frontal lobe corresponds to the frontal pole. Just in front of field 24, in a narrow area parallel to it, is Brodmann's field 32. Under the lower portion of the inferior and anterior end of the cingulate sulcus lies the mesial portion of the orbital region of the frontal lobe. In the mesial view, we can recognize a small anteroposterior sulcus, the suborbital sulcus (SOrbS). In the inferior view, the most mesial, anteroposterior sulcus is the medial orbital sulcus (mOrbS) or olfactory sulcus, which marks the lateral border of the gyrus rectus (Grec). Lateral to this sulcus we find a host of orbital sulci forming a pattern reminiscent of the letter H and usually known as Hshaped sulci (HsS). These sulci help define the anterior, posterior, medial, and lateral orbital gyri (aOrbG, pOrbG, mOrbG, and lOrbG, respectively). Brodmann's field 11, 12, 13, 14, and 15 occupy this region. Brodmann's field 25 is located in the most posterior and mesial region of the orbital surface of the frontal lobe. The insula is completely buried under the frontoparietal opercula and the anterior and superior sector of the superior temporal gyrus. When these are excised, a large oval shaped region of cortex is made visible (see Figs. 2-11, 2-12).

The insula is limited by the circular sulcus. The insula is divided into anterior and posterior sectors. Located anteriorly we find the anterior or short insular sulci, which serve as limits to the anterior or short insular gyri; posteriorly we find the posterior or long insular suki, which limit the posterior or long insular gyri. In Figures 2-7,2-8, and 2-9, the dotted lines delineate the approximate limits of Brodmann's cytoarchitectonic regions. It is important to realize that no visible landmarks correspond to these borders. All we can currently do is venture on approximations, which continues to rely on the informative maps of Brodmann and his followers (e.g., Sarkissow et al., 1955; Braak, 1978). Fortunately, this task is made easier by the fact that some Brodmann's areas do follow sulcal patterns. As a result, talking about areas 40 and 39 is equivalent to talking about the supra-marginal and the angular gyrus, and mentioning area 37 is certainly more efficient than referring to the posterior sector of the middle, inferior and 4th temporal gyri. As a complement to the reading of this chapter, I recommend Duvernoy (1999), an anatomic description of postmortem brains, and Ono et al. (1990), a detailed study of sulcal variability.


[17]

Figure 2-1

Lateral views of Dolicho with marked sulci. See text for details.

[18]

Figure 2-2 Lateral views of Dolicho with marked gyri. See text for details.

[19]

Figure 2-3

Mesial views of Dolicho with marked sulci. See text for details.

[20]

Figure 2-4 Mesial views of Dolicho with marked gyri. See text for details.

[21]

Figure 2-5

Bottom and top views (top) and front and back views (bottom) of Dolicho with marked sulci. See text for details.

[22]

Figure 2-6 Bottom and top views (top) and front and back views (bottom) of Dolicho with marked gyri. See text for details.

[23]

Figure 2-7

Lateral views of Dolicho with Brodmann's cytoarchitectonic areas marked on the same views seen in Figure 2-2. See text for details.

[24]

Figure 2-8

Mesial views of Dolicho with Brodmann's cytoarchitectonic areas marked on the same views seen in Figure 2-4. See text for details.

[25]

Figure 2-9

Bottom and top views (top) and front and back views (bottom) of Dolicho with Brodmann's cytoarchitectonic areas marked on the same views seen in Figure 2-6. See text for details.

[26]

Figure 2-10

Unroofing of the superior temporal gyrus. The frontal and parietal lobes were removed above the sylvian fissure and above a straight line drawn from the end of the sylvian fissure to the edge of the brain (top), according to the method described by Geschwind and Levitzky (1968). Observation from above (bottom) allows inspection of the superior surface of the STG. A transverse running sulcus and gyrus are prominently seen. The

transverse temporal sulcus is on the bottom left. The transverse gyrus of Heshl is colored red on the bottom right. It corresponds roughly to Brodmann's fields 41/42, the primary auditory cortices. Behind HG is a triangular region, colored green. This is known as the planum temporale, and corresponds to auditory association cortex, Brodmann's field 22, as does the rest of the superior temporal gyrus.

[27]

Figure 2-11

Image of the left and right insula after portions of the frontal, parietal, and temporal lobes which cover it have been removed. Sulci are marked. See text for details.

[28]

Figure 2-12

Image of the left and right insula after portions of the frontal, parietal, and temporal lobes covering it have been removed. Gyri are marked. See text for details.

[29]


Chapter 3 Exterior Description of a Brachicephalic Brain

A nother normal brain is depicted in this section, that of a 43-year-old, rightjL~Vhanded Caucasian woman. The overall configuration of this brain is quite different from the one in the previous chapter. It is a brachicephalic brain, and I refer to it as Brachi-1. As with Dolicho, I begin at the outer surface and identify the major sulci (Figs. 3-1, 3-3, 3-5). Figures 3-2, 3-4, and 3-6 show the gyri. Figure 3-7 shows both the sulci and the gyri in the superior surface of the superior temporal gyrus. The description of the sulci and gyri in Chapter 2 entirely applies here. The images in this chapter should be compared with the corresponding images in the previous chapter. No images of cytoarchitectonic fields are shown for this brain.

[31]

Figure 3-1

Lateral views of Brachi-1 with marked sulci. See Chapter 2 for details.

[32]

Figure 3-2

Lateral views of Brachi-1 with marked gyri. See Chapter 2 for details.

[33]

Figure 3-3

Mesial views of Brachi-1 with marked sulci. See Chapter 2 for details.

[34]

Figure 3-4 Mesial views of Brachi-1 with marked gyri. See Chapter 2 for details.

[35]

Figure 3-5

Bottom and top views (top) and front and back views (bottom) of Brachi-1 with marked sulci. See Chapter 2 for details.

[36]

Figure 3-6

Bottom and top views (top] and front and back views (bottom) of Brachi-1 with marked gyri. See Chapter 2 for details.

[37]

Figure 3-7

Unroofing of the superior temporal gyrus. See Chapter 2 and legend of Figure 2-10 for details.

[38]

Chapter 4 Exterior Description of Another Brachicephalic Brain

A nother brachicephalic brain, Brachi-2, is shown in this chapter. This is the JLJLbrain of a 34-year-old, fully right-handed man of Asian descent. The reason for depicting a second brachicephalic brain is that brachicephalic brains vary quite considerably among themselves. The difference between Dolicho and Brachi-2 is even more pronounced than that between Dolicho and Brachi-1. The overall configuration shows a shorter anterior-posterior diameter and a larger left-right diameter, best appreciated by comparing Figures 4-5 and 4-6 with Figures 2-5 and 2-6. Compare also to Figures 3-5 and 3-6. The external morphologic description remains the same, but note how the different overall configuration leads to different structures appearing in the slices obtained through this brain (see Chapter 9). In spite of these differences, however, the sulci and gyri are the same as described in Chapter 2 and the proportions of the brain, lobes, and gyri are the same as those in the Caucasian brains depicted in Chapter 6. This brain shows a good example of a partially doubled Heschl's gyrus (see Fig. 4-7). Also, note that in the right hemisphere there is a clear middle frontal sulcus> (MFS), which divides the middle frontal gyrus in two.

[39]

Figure 4-1

Lateral views of Brachi-2 with marked sulci. See text of Chapter 2 for details.

[40]

Figure 4-2

Lateral views of Brachi-2 with marked gyri. See text of Chapter 2 for details.

[41]

Figure 4-3

Mesial views of Brachi-2 with marked sulci. See text of Chapter 2 for details.

[42]

Figure 4-4

Mesial views of Brachi-2 with marked gyri. See text of Chapter 2 for details.

[43]

Figure 4-5

Bottom and top views (top) and front and back views (bottom) of Brachi-2 with marked sulci. See text of Chapter 2 for details.

[44]

Figure 4-6

Bottom and top views (top) and front and back views (bottom) of Brachi-2 with marked gyri. See text of Chapter 2 for details.

[45]

Figure 4-7

Unroofing of the superior temporal gyrus. See text of Chapter 2 and legend of Figure 2-10 for details.

[46]

Chapter 5 An Alphabet of Normal Brains

C

hapter 2 provided a description of the different sulci on the brain's lateral and mesial surfaces based on the most common appearance of those structures. The purpose of this chapter is different. Rather than concentrating on "average" neuroanatomic design, I emphasize the large range of variation that entirely normal structures may exhibit. Neuroanatomic interpretations are unlikely to be accurate unless such diversity is taken into account. This chapter is made up of a collection of normal adult brains, labeled A-Z. Each brain is depicted in its lateral and mesial surfaces, seen from the right and left, from above and below. The reader should inspect these brains and appreciate the large variance among individual specimens and even between the two hemispheres of the same brain. Not all sulci were identified so that the surfaces could be left uncluttered but the main landmark sulci highlighted. Unmarked sulci should be easy to recognize using the description provided in Chapter 2. Most of the brains depicted in this chapter belong to persons below age 50 (range 18-50, mean 29 years). The last six belong to persons 61-79 years of age (mean 70). As was to be expected, the sulci in the latter group are wider than those in the younger group. However, there are some remarkable exceptions. Brain W (of a 75-year-old woman) has notably tight sulci, not much different from those of brain D (of a 22-year-old woman). On the other hand, brain K (of a 50-year-old man) shows remarkably wide sulci, not that different from those in the majority of older subjects. Half the brains are from women (always depicted on the right) and half from men (depicted on the left). Brains S and T are from women that happen to be identical twins. The pairs were matched, as well as possible, for handedness and age, providing a realistic comparison of the morphology of male and female brains. Note, for instance, how the gender difference that has been reported for the splenium, the posterior sector of the corpus callosum, can easily be challenged. Compare the splenium in brains C and D (of a man and a woman, respectively): neither shows the "typical" enlargement attributed to the

[47]


[48]

female brain, although both brains M and N (also of a man and a woman, respectively) show such an enlargement. Comparison of brains O and P or U and V shows the bulging of the splenium in men but not women. The reported difference can be seen in brains A and B as well as in H and G. Out of the 12 female brains, six show bulging of the splenium and six do not; out of the 12 male brains, four show splenial bulging and eight do not. The twin brains, T and S (both women), show bulging of the splenium. A mixture of these presentations can also be seen in Chapter 6. For example, the pair 14F and 14M presents with a typical bulging pattern, while the pair 7F and 7M shows more bulging in the man. No systematic difference between the genders can be found on inspection of the sulcal pattern. What is remarkable in the sulcal pattern is the variability among subjects, even between the right and left hemispheres of the same person. Marked differences can be appreciated even in the major sulci and all the more so in secondary or tertiary sulci. The fact that the sulci in the two twin brains are much closer to each other than any other two brains in the collection is interesting. However, equally interesting is the fact that even the sylvian fissure and the central sulcus, two sulci that develop early, are quite different in these two persons whose genetic makeup is the same. (See Figure 1-2 to appreciate the lack of superposition of these sulci when the brains are morphed to the same space.) One other purpose of this chapter is to compare brains according to handedness. The chapter begins with brains from extreme right-handers, brains A-H (handedness scores of+ 85 to +1000 in the Oldfield-Geschwind questionnaire). It continues with four brains from extreme left-handers, brains I-L (scores of —80 to —100) and six brains of subjects with mixed handedness, brains M-R (scores of —30 to +65). Both twins are fully right-handed, as are the six older subjects. The feature of external morphology most connected to right handedness (and, by extension, with left hemisphere dominance for language) is the course of the sylvian fissure. We expect it to be longer and to terminate with a downward turn in the left hemisphere and to be shorter and to have a terminal upswing in the right hemisphere. Such a typical sylvian fissure can be seen in brains D, Y, and Z, all strong right-handed subjects; but it is also found in brain K, that of a left-handed man (—80), and in brain N, that of a woman with mixed handedness (—30). The reverse pattern might be expected in strong lefthanders, but that is not the case in the exemplars at hand. The remaining three strong left-handers (brains I, J, and L) have rather symmetrically coursing sylvian fissures, as happens with most mixed-handedness cases. There is a very good example of a reversal of the sylvian fissure pattern (downward turn on the right and upward turn on the left) in brain G, that of a fully right-handed man ( + 100), as well as in several of the brains seen in Chapter 6, where all subjects are strongly right-handed; see for instance the pair 17 F and 17M). Also, one of the most typical right-left asymmetry patterns in the whole of this chapter is that in brain O, a man of mixed handedness.

Chapter 5 Figures

[49]

Figure 5-1

Brain A. Right-handed (+90) man, 27 years of age.

[50]

Figure 5-2 Brain B. Right-handed (+90) woman, 27 years of age.

[51]

Figure 5-3

Brain C. Right-handed ( + 100) man, 24 years of age.

[52]

Figure 5-4 Brain D. Right-handed (+85) woman, 22 years of age.

[53]

Figure 5-5

Brain E. Right-handed (+90) man, 20 years of age.

[54J

Figure 5-6

Brain F. Right-handed ( + 100) woman, 18 years of age.

[55]

Figure 5-7

Brain G. Right-handed ( + 100) man, 32 years of age.

[56]

Figure 5-8 Brain H. Right-handed (+90) woman, 28 years of age.

[57]

Figure 5-9

Brain I. Left-handed (-100) man, 42 years of age.

[58]

Figure 5-10

Brain J. Left-handed (-100) woman, 39 years of age.

[59]

Figure 5-11

Brain K. Left-handed (-80) man, 50 years of age.

[60]

Figure 5-12 Brain L. Left-handed (-95) woman, 50 years of age.

[61]

Figure 5-13

Brain M. Mixed-handed ( — 30) man, 28 years of age.

[62]

t

Brain N. Mked-handed ( — 30) woman, 26 years of age.

[63]

Figure 5-15

Brain O. Mixed-handed (—25) man, 19 years of age.

[64]

Figure 5-16

Brain P. Mixed-handed (+35) woman, 31 years of age.

[65]

Figure 5-17 Brain Q. Mixed-handed (+65) man, 29 years of age.

[66]

Figure 5-18

Brain R. Mixed-handed (+40) woman, 22 years of age.

[67]

Figure 5-19

Brain S. Right-handed ( + 100) woman, 23 years of age. Identical twin of the woman in Figure 5-20.

[68]

Figure 5-20 Brain T. Right-handed ( + 100) woman, 23 years of age. Identical twin of the woman in Figure 5-19.

[69]

Figure 5-21

Brain U. Right-handed ( + 100) man, 73 years of age.

[70]

Figure 5-22

Brain V. Right-handed ( + 100) woman, 68 years of age.

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Figure 5-23 Brain W. Right-handed ( + 100) man, 75 years of age.

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Figure 5-24

Brain X. Right-handed (+100) woman, 79 years of age.

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Figure 5-25

Brain Y. Right-handed (+95) man, 61 years of age.

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Figure 5-26

Brain Z. Right-handed ( + 100) woman, 63 years of age.

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Chapter 6 Quantifying Neuroanatomic Differences In collaboration with John S. Allen and Joel Bruss

T

his chapter demonstrates that, in addition to the qualitative analysis shown in the previous sections, modern imaging techniques can be used for the quantitative investigation of brain structure. Three-dimensional (3-D) magnetic resonance imaging (MRI) allows us to identify and measure surface brain structures, deep structures can be delineated using a combination of twodimensional (2-D) slice orientations, and a number of new techniques permit the quantitative study of structural MRIs: for example, the automated segmentation of MRIs into gray matter (GM), white matter (WM), and cerebral spinal fluid (CSF) provides quantitative information about the global and regional composition of the brain (Fig. 6-1) (Grabowski et aL, 2000). Useful quantitative data on the structure of the brain can be obtained with the relatively small number of metrics relevant for analyzing MR images. These metrics include linear and angular measurements of surface structures, such as sulci, and volumetric measurements of any specific three-dimensional structure or region of interest (ROI). Automated tissue segmentation allows us to determine GM and WM volumes of structures and to calculate the ratio of the two in an ROI or the gray matter density of a region (GM/[GM + WM]). Quantitative analysis of brain structures with MRI has become a valuable research tool over the past decade. However, when reading this literature, it is important to keep in mind that such analysis of brain MR images is not standardized. Comparisons across studies conducted by different research groups need to take into account factors such as voxel size and slice thickness, which determine the spatial resolution of the MR images. Quantitative studies also employ different sampling and parcellation methods, which may contribute to variability in the results obtained by different groups. Given the rapid pace of technological development in the field and the vagaries of anatomic parcellation, methodologic issues are of particular importance in meta-analyses of MRI studies (e.g., Brierly et al., 2002). In this chapter, we present results based on extensive quantitative studies of brain size conducted in 87 healthy, right-handed adults between the ages of 22 and

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88 years (44 men and 43 women) and in 25 congenitally deaf adults (Allen et al., 2002,2003a-c; Emmorey et al., 2003). These studies demonstrate the value of MRI for understanding how brain size and the proportional composition of the brain's major lobes and sectors vary according to gender, age, disease, or congenital abnormality. Data from these studies allow us to address basic questions about the development, evolution, and function of the human brain (Allen et al., 2004a).

A Comment on Automated Methods for Quantitative Magnetic Resonance Imaging Research Given that tracing ROIs on contiguous MRI slices is such a laborious undertaking (see below), it is not surprising that various researchers have tried to develop automated methods to parcellate the brain (for examples of automated methods, see Nopoulos et al., 2000; Good et al., 2000; Sowell et al., 2003). These automated methods ease the task of data collecting, although there is an inevitable trade-off in loss of precision. Brain structures are not identified by anatomic landmarks but, rather, according to statistical brain maps. Another attraction of automated methods for determining regional brain volumes (or to compare relative volumes across subject groups) is that they allow investigators with little neuroanatomic expertise to conduct neuroanatomic research. While there is nothing inherently wrong with such facilitation, there are often unforeseen consequences when a researcher depends on the output from a "black box" at a critical step in data analysis. Neuroimaging researchers need to keep in mind that the MRI "brains" they analyze are highly processed digital signals rendered into virtual structures, and anatomical knowledge is of the essence to perform anatomically based research. One of the main drawbacks of automated methods for volumetric brain research is that all require resizing brains into a common anatomic space before analysis can be done (e.g., Tailarach and Tournoux, 1988). Although resizing serves to "control" for brain size in some comparative contexts, the resizing itself may attenuate differences between groups of interest. Furthermore, resizing methods may treat different regions of the brain differently, which may distort regional volume relationships both within and between individual brains; there is the possibility for significant errors when the volumetric analysis is carried out in resized rather than "original" brains (Allen et al. 2004b). Normative data on brain volume are becoming more widely available in publications and via sources such as the Internet Brain Volume Database (www.cma.mgh. harvard.edu/ibvd/). This database, derived from more than 80 publications, provides a continuously updated source of volumetric MRI data organized by anatomic region, age, sex, and pathology. Since brains vary by size and tissue composition (i.e., amount of GM versus WM) between the sexes and across the life span, it is essential to develop an accurate picture of normal variation before investigating changes in brain size or composition that might be associated with various diseases or conditions. As mentioned above, however, investigators need to be wary about the methodologic sources of variability (e.g., have the brains been resized before quantification?) when examining patterns of biologic variability obtained by combining data from different research sources.

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Method and Rules for Pa reel lat ion of the Major Lobes Quantifying Neuroanatomic

The process of dividing brain structures into various regions is called parcellation. The ultimate goal of parcellation in MRI research is to identify and delineate neuroanatomic regions that are of functional, developmental, pathologic, or evolutionary significance. Different researchers have used different methods to obtain brain parcellations. Here, we describe the principles used in our laboratory. For ROIs that are fully or partially bounded by structures seen on the surface of the hemisphere, parcellation proceeds first by marking the limiting structures on the surface of the 3-D rendered brain; these markings are transferred automatically to 2-D slices of the brain (Frank et al, 1997). Tracing of ROIs is done by hand on contiguous slices. The area traced in each ROI is multiplied by the slice thickness to determine a slice volume. Then, the volumes of each slice are summed to create a volume for the 3-D ROI structure. To maintain a consistent orientation for tracing ROIs, all brains are realigned into a common position. Consistent position is necessary to ensure that those ROI limits that have to be set using "arbitrary" lines and planes will be set in the same fashion across different brains. Consistent position also helps improve intertracer reliability since brain structures appear quite differently in different slice orientations. The brains are reoriented so that the coronal planes are perpendicular to a plane containing the anterior and posterior commissures (the ac-pc plane). The criteria followed in our laboratory for the parcellation of the frontal, temporal, parietal, and occipital lobes, along with the insula and cingulate gyrus, are presented below (see Fig. 6-2). The quantitative volumetric results of this parcellation applied to 46 healthy, right-handed adults have been presented fully in Allen et al. (2002, 2003b) and are also discussed in subsequent sections of this chapter.

Differences

Frontal Lobe

The major sulcal boundaries of the frontal lobe are the sylvian fissure, the central sulcus, and the cingulate sulcus. The superoposterior boundary on the mesial surface is the ascending branch of the cingulate sulcus and the mesial extension of the central sulcus. Since these sulci do not join, an arbitrary line linking the two is drawn along the surface of the brain in the parasagittal cut, in which the end of the central sulcus is seen. The cingulate gyrus and insula are excluded from the frontal lobe, and, because the ascending branch of the cingulate sulcus is posterior to the mesial termination of the central sulcus, a small sliver of the mesial portion of the postcentral gyrus (parietal lobe) is necessarily included in the frontal lobe ROI. Temporal Lobe

The temporal lobe is bounded by the sylvian fissure superiorly and the parahippocampal fissure mesially. On the mesial surface, the posterior boundaries are formed by the occipital cut (see Occipital Lobe, below) and an arbitrary line drawn from the junction of the occipitoparietal and calcarine sulci to the most inferior point of the splenium of the corpus callosum. On the lateral surface,

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the boundary between the temporal and occipital lobes is formed by the occipital cut. An additional limiting line is drawn from the end of the sylvian fissure to a point along the lateral portion of the occipital cut. This point is one-quarter of the distance from the preoccipital notch (point 3) to the occipitoparietal sulcus (point 1), as measured along the surface of the brain in the coronal slice containing the occipital cut. This line forms the boundary between the temporal and parietal lobes. Occipital Lobe The occipital lobe has no "natural" sulcal boundaries. We consider it limited anteriorly by the occipital cut (see below), with the exception of the superomesial boundary, where instead the occipitoparietal sulcus is used to separate the occipital from the parietal lobe. The occipital cut forms the anterior boundary of the occipital lobe and the posterior boundaries of the parietal and temporal lobes. It is a plane defined by the following three points: the superior end of the occipitoparietal sulcus (point 1) and the junction of the occipitoparietal and calcarine sulci (point 2) on the mesial surface and the preoccipital notch on the lateral surface (point 3). This oblique plane is automatically rendered as a slice by the Brainvox image analysis program (Frank et al., 1997). On this oblique slice, the hemisphere being parcellated is traced, generating the limiting line on the surface of the brain that corresponds to the "cut." In coronal slices, this line appears as two points on the surface of the brain. Parietal Lobe The boundaries are the central sulcus, sylvian fissure, ascending branch of the cingulate sulcus, occipital cut, and the arbitrary line separating it from the temporal lobe as described above. The parietal lobe is separated from the posterior cingulate by a line drawn from the origin of the ascending branch of the cingulate sulcus to the junction of the occipitoparietal and calcarine sulci. Cingulate Gyrus We treat the cingulate gyrus as a separate structure instead of including it under the frontal and parietal lobes. The cingulate gyrus is bounded by the cingulate sulcus and the callosal sulcus. The inferior boundary of the anterior cingulate gyrus is formed by a line drawn from the antero-inferior end of the sulcus to the posterior point of the rostrum of the corpus callosum (this corresponds to the anteroinferior end of the callosal sulcus). The posterior cingulate is separated from the parietal and temporal lobes by the two arbitrary lines described above. In cases of double cingulate sulci, the outer sulcus is chosen as the boundary for the gyrus. Insula

We also treat the insula as a separate structure. The insula is defined by the circular sulcus, which can be clearly seen in coronal cuts. Anteriorly, the insula may appear as a small amount of gray matter embedded in the surrounding tissue of the frontal lobe. The insula is separated from the rest of the hemisphere [80]

by a line linking the deepest extent of both ends of the circular sulcus. When the claustrum becomes visible, the line is edited to exclude it.

Quantifying Neuroanatomic Differences

Proportions of the Major Lobes The parcellation of a group of 46 healthy, right-handed individuals between the ages of 22 and 49 years (Figs. 6-3 to 6-10) indicates that there are no sex differences in the proportional representations of the major lobes (lobe volume divided by hemisphere volume) and that volumetric variation is consistently greater than variation in proportions (Allen et al., 2002). In both men and women, the frontal lobes comprise about 38% of the hemispheres (range 36%-43%), the temporal lobe about 22% (range 19%-24%), the parietal lobe about 25% (range 21%-28%), and the occipital lobe about 9% (range 7%-12%); the cingulate gyrus comprises about 4.3% of the left hemisphere and 3.8% of the right, reflecting a sulcal asymmetry that will be discussed below. Although there is not major proportional variability for any of the principal lobes, individual variation in lobe proportions does occur. For example, after controlling for brain size, there is a significant negative correlation between frontal and parietal lobe volumes: people with large parietal lobes tend to have small frontal lobes and vice versa. Subjects 11F (Fig. 6-6) and 6M (Fig. 6-5) have proportionally large frontal and small parietal lobes. A similar but weaker inverse relationship can also be seen between the temporal and occipital lobes (e.g., subject 1M in Fig. 6-3). The inverse relationship between the frontal and parietal lobes suggests that the position of the central sulcus, which is one of the earliest sulci to appear in development, is a critical determinant of the relative sizes and proportions of these lobes. Theories that suggest relative frontal lobe expansion over the course of human evolution (e.g., Deacon, 1997) are not supported by this finding, since the selection for individuals with relatively larger frontal lobes would also select for people with relatively smaller parietal lobes. There is no evidence for parietal lobe contraction during human evolution, nor would that be expected given that tool use, a hallmark of hominid cognitive evolution, depends on parietofrontal circuits (Johnson-Frey, 2003). Further evidence against frontal lobe expansion in hominid evolution comes from comparative anatomy. Volumetric MRI studies suggest that the proportional volumetric representation of the principal lobes of the human brain follows the pattern seen in our closest relatives, the great apes (see Fig. 1-3) (Semendeferi and Damasio, 2000; Semendeferi et al., 2002). In general, across mammalian species, the proportional representation of different parts of the brain tends to remain fairly constant, even while volume varies tremendously (Jerison, 1973; Finlay and Darlington, 1995; Finlay et al., 2001). It comes as no surprise then that within our own species volumetric variability exceeds proportional variability. Brain Volume and Tissue Composition: Sex Differences Both postmortem and MRI volumetric studies of the brain have found that on average, men's brains are larger than women's brains (e.g., Pakkenberg and Voight, 1964; Ho et al., 1980; Skullerud, 1985; Peters et al., 1998; Courchesne [81]


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et al., 2000) but that women have a higher proportion of gray matter (versus white matter) than men do (Filipek et al, 1994; Passe et al., 1997; Peters et al., 1998; Gur et al., 1999). The overall size difference remains even after controlling for body size (Holloway, 1980; Peters et al., 1998; Nopoulos et al., 2000). Similarly, the gray-white difference is also present after controlling for brain size: if one compares a male and a female brain with the same overall volume, the woman's brain will contain, on average, more gray matter and less white matter than the man's brain (Peters et al., 1998; Gur et al., 1999). We have studied volumetric sex differences in brain structures (Allen et al., 2002, 2003b) in the group of 46 healthy, right-handed individuals between the ages of 22 and 49 years mentioned above. There were 23 men (mean age 32.1 years) and 23 women (mean age 32.6 years) in the group. On average, male brains are about 12% larger than female brains (left hemisphere and left hemicerebellum: mean 618.9 cc, standard deviation [s.d.] 54.7 for men and 547.0 cc, s.d. 47.8 for women; right hemisphere and right hemicerebellum: mean 621.7 cc, s.d. 58.3 for men and 552.7 cc, s.d. 49.5 for women). Male brains were no more variable than female brains. Although there was not a significant difference in size between the two hemispheres, both men and women were more likely to have larger right rather than left hemispheres. In general, the hemisphere patterns hold for each of the major lobes and substructures of the brain. However, the occipital lobe appears to be somewhat less sexually dimorphic than other regions. Segmentation of the brain into gray and white matter provides additional insights into the volumetric differences between the sexes. As discussed above, women (left hemisphere gray/white ratio: mean 1.35, s.d. 0.09; right hemisphere: mean 1.35, s.d. 0.09) tend to have relatively more gray matter than men (left hemisphere gray/white ratio: mean 1.27, s.d. 0.10; right hemisphere: mean 1.25, s.d. 0.10). Statistical analyses indicate that the higher gray/white ratio in women is not simply a matter of brain size (if the brain were simply a sphere, the surface/volume ratio would increase as the volume decreased). For example, the cerebra of 7F (Fig. 6-5) and of 16M (Fig. 6-8) are about the same size, 1,020 cc; but the gray/white ratio of the woman is 1.37, while that of the man is 1.10. The sex difference in cerebral volume is due more to differences in white matter volume than gray matter: analyses of covariance indicate that the gray/white ratio difference between the sexes disappears when controlling for WM volume, indicating that it is variability in white matter volume that most profoundly influences this relationship (Allen et al., 2003b). There is substantial variation among regions in the relative composition of gray and white matter. This is not surprising given the relative amounts of cortex and white matter core that are found in different parcellated regions (e.g., occipital versus frontal lobes). On the other hand, some gray-white composition patterns may reflect other factors. For example, effect size statistics indicate that the right parietal lobe is the most sexually dimorphic for the gray/white ratio compared to all other regions of the brain (female gray/white ratio: mean 0.95, s.d. 0.08; male: mean 0.85, s.d. 0.08). This is due to the fact that women have nearly as much gray matter in this region as men (59.8 cc versus 62.5 cc), while at the same time they have substantially less white matter (63.0 cc versus 74.2 cc). While the functional significance of this pattern is not yet clear, it could be a result of the distribution of sex steroid receptors in the brain (Reiss et al., 1995; Goldstein et al., 2001).

In terms of sex differences, a region of the brain that has drawn much attention over the years is the corpus callosum (CC) (de Lacoste-Utamsing and Holloway, 1982; Bishop and Wahlsten, 1997). Although some studies have shown that it might be larger in women than men, most in vivo neuroimaging studies have shown that it is larger in men, reflecting the overall volume difference (e.g., Sullivan et al., 2001). Earlier studies based on postmortem material may not have controlled for the effects of age when comparing men and women, which could certainly have led to spurious results concerning sexual dimorphism in the CC. The CC is a highly variable structure, as can be noted by inspection of the mesial surfaces of the 46 brains presented in Figures 6-3 to 6-10. Subjects 6F and 7M (both Fig. 6-5) have proportionally small CCs, while 14F (Fig. 6-7) and 19M (Fig. 6-9) have relatively large CCs for their respective total brain volumes. Although quantitative studies of the corpus callosum have traditionally considered the surface area of the structure (as it appears on the mesial surface when the brain is bisected through the hemispheric fissure), in our studies we have defined it as a three-dimensional structure encompassing the band of midline white matter inferior to the cingulate gyrus and superior to the lateral ventricles (see Allen et al., 2002, for a detailed description). Our results confirm that it is significantly larger in men than women (10.6 cc, s.d. 1.62 vs. 9.68 cc, s.d. 1.26). However, the corpus callosum makes up a significantly larger proportion of the total white matter in women (mean 0.0236, s.d. 0.0026) than in men (mean 0.0219, s.d. 0.0026). Since the corpus callosum is composed primarily of myelinated axonal fiber tracts, this result may indicate that a substantial portion of the overall white matter volume sex difference may be due to glial cells or blood vessels that contribute to the "white matter" seen in MR images. In other words, the "excess" of white matter relative to gray matter in men may not be due to a net increase in neuronal connectivity.


Interhemispheric Asymmetry In terms of overall volume, the brain is a fairly symmetric structure. However, there is a tendency for right-handed individuals to have a slightly larger right hemisphere (Allen et al., 2002). Some regions of the brain show pronounced asymmetries, while others are fairly symmetric (Toga and Thompson, 2003). For example, the left cingulate gyrus is substantially larger in volume than the right, especially in males: we found that the mean left cingulate gyrus volume was 23.4 cc compared to 19.7 cc in the right (Allen et al., 2002). This may be due to the fact that the left cingulate sulcus is more likely to be "doubled" on the left side rather than the right (Paus et al., 1996), although the opposite pattern also occurs with some frequency. See brains C, E, and G, in Chapter 5 subjects and 8M (Fig. 6-5), 3M (Fig. 6-4), and IF (Fig. 6-3) in this chapter for examples of cingulate sulcus asymmetry. Brain A shows a symmetric pattern in the cingulate sulcus, while brains O and K show reversed asymmetry. The frontal and occipital petalias comprise another well-known cerebral asymmetry (Chui and Damasio, 1980; Zilles et al., 1996). Seen from above or in some axial sections, the human brain often protrudes slightly anteriorly in the right hemisphere (frontal petalia) and posteriorly in the left hemisphere [83]


(occipital petalia). In practical terms, the right frontal lobe goes farther into the frontal bone than the left, and the left occipital lobe goes farther back into the occipital bone than the right, creating bone depressions, the petalias. We have found that the petalia may correspond to asymmetries in the distribution of white matter (but not gray matter), since white matter volumes tend to be larger in the right frontal and left occipital lobes compared to their opposites (Allen et al., 2003b). Brains B and C in Chapter 5 provide particularly good examples of the "typical" petalia pattern. One of the best-known asymmetries in the brain involves the planum temporale (PT) (Geschwind and Levitsky, 1968; Westbury et al., 1999). The PT includes all of the cortex on the superior surface of the temporal lobe that is posterior to Heschl's gyrus, terminating at the posterior end of the sylvian fissure (see Figs. 2-10, 3-7, and 4-7). In right-handers, this structure is clearly larger in the left hemisphere. In a recent study of 25 right-handed adults (14 women and 11 men), we found that the left PT is 23.6% larger in the left hemisphere compared to the right (Emmorey et al., 2003). Although it was once thought that this asymmetry might be an anatomic pattern that corresponded to the evolution of spoken language (Galaburda et al., 1978), recent research on great apes has shown that a larger left PT is something that we share with our closest relatives, who do not possess language (Gannon et al., 1998; Hopkins et al., 1998). The relationship among PT asymmetry, language dominance, and handedness is not clear (Moffat et al., 1998). Congenitally deaf individuals also have a larger left PT, indicating that the pattern does not arise as a result of the processing of spoken language (Emmorey et al., 2003; see discussion below). The course of the sylvian fissure provides another common instance of brain asymmetry, one that in all likelihood is related to PT asymmetry. In righthanders, the sylvian fissure tends to turn upward in the right hemisphere and to extend more posteriorly in the left (Rubens et al., 1976). Since the PT is defined by the extension of the sylvian fissure, this asymmetry is usually consistent with the left PT being larger than the right. The angle of the posterior sylvian fissure can be quantified in MR images by taking the ac-pc plane as a reference. In groups of left- and right-handers studied in our laboratory, we have found that, while right-handers have the expected pronounced upward course in the right rather than left posterior sylvian fissure (average of 36.7° upward angle in the right hemisphere compared to 22.6° in the left), there is no such asymmetry in left-handers (31.5° angle in the left hemisphere and 33.4° in the right). These patterns can be visually confirmed by examining the sylvian fissures of the brains of the 46 right-handed individuals illustrated in this chapter and comparing them to the left-handed individuals represented in brains I-O in Chapter 5.

Brain Volume and Tissue Composition: Aging Effects Age is a fundamental component of human variation, and changes in brain size and composition over the life span reflect this (Raz, 1999). Over the past decade, volumetric MRI analyses have added much to our understanding of many as-

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pects of brain development and aging (e.g., Cowell et al., 1994; Coffey et al., 1998; Tang et al., 2001; Sowell et al., 2003). The human newborn has a brain that is about 30% of adult size, and brain growth is rapid until the age of 2 years. By the age of 2, the average child's brain volume is over 1,000 cc, and growth contipues, at a much slower rate, between the ages of 2 and 14 years (Courchesne et al., 2000). It has long been known that the aging brain is characterized by volume reduction, with an increase in the size and depth of sulci. Recent MRI research indicates, however, that age-associated brain atrophy does not occur in a uniform manner, although different studies have produced conflicting results. For example, age-associated volume reductions have been more pronounced in the frontal lobe compared to other brain regions (Cowell et al., 1994; Jernigan et al., 2001), although others have found that the frontal and temporal lobes age at similar rates (Bartzokis et al., 2001). Within the temporal lobe, the hippocampus may be more sensitive to age than the amygdala (Pruessner et al. 2001). Several aging studies have found that gray and white matter volumes do not change over the life span at the same rate (Jernigan et al., 2001; Bartzokis et al., 2001; Guttman et al., 1998). Gray matter volume declines throughout adulthood and into old age at a more or less linear rate. By contrast, some studies have shown that white matter volumes may actually increase slowly through adulthood, peaking in the 40-50 year range (Bartzokis et al., 2001). After 60 years of age, there is a precipitous decline in white matter volume (Guttman et al., 1998). Brain aging patterns in men and women are largely similar, although some studies show that the gray matter decline may be slower in women than in men (Cowell et al., 1994). We have analyzed aging patterns in the gray and white matter in a group of 87 healthy, right-handed adults (44 women and 43 men), ranging in age from 22 to 88 years (Allen et al., 2003a). Regression analyses indicate that for both men and women gray matter declines linearly across the life span, while white matter volumes remain steady or actually increase slightly throughout much of adulthood, peaking around age 45-55 years. This is followed by the precipitous decline of white matter volume noted above. These patterns hold approximately for the hemispheres and for the principal lobes. Considering the cerebrum as a whole, we can predict, based on the regression equations, that from age 30 to 70 years white matter volume will decrease 6.4% in women and 5.5% in men and that gray matter will decline 9.9% in women and 9.1% in men. Over this period, the gray/white ratio will drop from 1.29 to 1.26 in women and from 1.22 to 1.20 in men. When we compare volume predictions at 30 and 80 years of age, the gray matter volume shows a decrease of 12.4% in women and 11.4% in men and the white matter decrease is 25.0% in women and 21.6% in men. The predicted gray/white ratio increases to 1.50 in women and 1.43 in men, reflecting the fact that white matter loss occurs much more quickly past the age of 70 than gray matter loss. Brains U through Z in Chapter 5 are from healthy subjects older than 60 years. They demonstrate that normal aging patterns and individual variations in aging become important components of variability in the brain morphology of normal, healthy subjects greater than 60 years of age. Brain U, which comes


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from a 73-year-old male, exhibits the pronounced sulcal widening that results from loss of gray and, especially, white matter. By contrast, brain Y, which belongs to a somewhat younger individual, shows only a mild degree of sulcal widening. The visual difference between brains U and Y is confirmed by quantitative measures: the gray/white ratio for brain U is 1.38, while that for Y is 1.19. This indicates that white matter loss in brain U is markedly more advanced than it is in brain Y, thus the higher gray/white ratio. Individual variation in aging can be seen by comparing brain X, which belongs to a 79-year-old female, to brain U. Despite the fact that the brain X subject is 6 years older than the brain U subject, her brain is markedly less atrophied.

Heschl's Gyrus in Congenitally Deaf Individuals Earlier, we mentioned that congenitally deaf subjects appear to have the same asymmetry in the planum temporale as hearing subjects (Emmorey et al., 2003). Heschl's gyrus (HG), the small transverse gyrus located on the surface of the temporal lobe, is the approximate site of the primary auditory cortex (Rademacher et al., 1993, 2001). By comparing HG in congenitally deaf and hearing individuals, it may be possible to gain insight into the impact the sensory environment has on the development of a specific neural structure. We investigated a group of 25 congenitally deaf individuals and 25 age- and sex-matched hearing comparison subjects with respect to gray and white matter composition of several structures in the temporal lobe, including the superior temporal gyrus as a whole (its posterior sector, the planum temporale), and Heschl's gyrus (Emmorey et al., 2003). Heschl's gyrus is defined anteriorly by the first transverse temporal sulcus and posteriorly by Heschl's sulcus (the second transverse sulcus). When more than one sulcus is present, the most anterior one is used. Heschl's gyrus is visible on the superior surface of the temporal lobe in a "planum cut", a preparation in which the frontoparietal operculum has been removed. Accurate parcellation of HG is greatly facilitated using surface landmarks and multiple 2-D slice orientations. Although the planum temporale is similar in deaf and hearing subjects, we found that these two groups had differences in other structures. Most importantly, the gray/white ratio in Heschl's gyrus was significantly higher in deaf compared to hearing subjects. This appears to be due primarily to a reduction in white matter volume: after correcting for overall temporal lobe volume, there was no difference in Heschl's gyrus gray volume between deaf and hearing subjects but HG white matter volume was significantly smaller in deaf subjects. This result suggests that auditory deprivation from birth results in less myelination, fewer fibers projecting to and from the auditory cortex, and/or greater axonal pruning in the congenitally deaf.

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Figure 6-1

Automated segmentation of a magnetic resonance brain volume. Gray matter is represented in dark blue, white matter in cyan, and cerebral spinal fluid in red. Each figure is composed of

10 contiguous coronal slices, offset slightly to convey the threedimensional structure.

Figure 6-2

Parcellation of the major sectors of the cerebrum. Landmarks on the surface of the brain, such as sulci, are used to guide tracing of regions of interest (ROI) on contiguous coronal slices. In the top row, lateral and mesial views of the left hemisphere are presented; cyan line corresponds to the position of the coronal slice shown between the two hemisphere views. Parcellation of ROIs on this coronal slice is indicated by green lines. In the middle row, lateral and mesial views of the hemisphere are presented

with the major sectors colored in following parcellation on contiguous coronal slices (1.5 mm thick) through the whole brain. Four representative coronal slices demonstrating parcellation of the brain are presented in the bottom row; their positions are indicated by lines 1-4 on the lobes in the middle row. FL, red; PL, green; TL, blue; OL, yellow; Cing, magenta; Ins, teal. Itc, lateral temporal cut; oc, occipital cut; mpc, mesial parietal cut; mtc, mesial temporal cut. [87]

Figures 6-3 to 6-10 Lateral and mesial views of 46 parcellated brains with gray and white matter volumes (in cubic millimeters) for left and right hemispheres: 23 male (M) and 23 female (F) (females on the left and males on the right; brains are presented in descending order of total volume for each sex. All brain images are rendered to the same scale. The number following the subject number is the subject's age in years at the time of the magnetic resonance scan. Frontal lobe, red; parietal lobe, green; temporal lobe, blue; occipital lobe, yellow; cingulate gyrus, magenta.

IF 23 Frontal Temporal Parietal Occipital Cingulate

2F 26 Frontal Temporal Parietal Occipital Cingulate

Right

Gray 114884 83411 78785 37271 16523

White 110782 47503 79199 18675 4675

Right Gray White 107633 105901 66115 33063 67862 66734 34936 19498 21773 6519

Left

Gray 113646 81995 70367 37688 17825

White 111924 43274 71845 24531 7421

Left Gray 107064 76400 62501 29837 19682

White 95771 39474 65148 18854 7923

Figure 6-3 Parcellation of the cerebrum and volume data for male and female subjects 1 and 2.

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1M 23 Frontal Temporal Parietal Occipital Cingulate ^—m._

2M 46 Frontal Temporal Parietal Occipital Cingulate

Right

Gray 122890 99398 65851 29709 20852

White 122750 55995 79088 16714 6738

Right Gray White 111558 134797 88266 62083 81923 63373 32490 19343 15826 5523

^p»Left

Gray 118233 96384 71494 26771 19993

White 116544 54785 81579 18148 8393

Left Gray 112701 86714 63269 32941 15982

White 126925 58483 83031 23221 8931




Left

Right White Gray 92576 98659 71077 42683 74287 59917 21839 36471 15909 5143

Gray 92584 66126 63812 34294 15878

Right Gray White 105623 94858 75370 36539 65532 75778 31135 16326 14671 4570

Left Gray 105188 74198 62568 30098 14630

Right Gray White 96119 100259 63599 36764 63877 84901 29970 20185 14703 5150

Gray 98084 62479 63473 32286 11937

Left

White 99756 40536 75528 21412 7278

White 96042 36297 67674 18544 6395

White 99843 35724 79679 24749 6111




Right White Gray 111458 115500 91433 52965 82503 69649 23223 36805 5682 17836

Left Gray 109075 86375 72932 36197 21882

White 104765 48757 84460 24668 9390

Right White Gray 115368 116119 80601 45330 76742 86637 33961 20707 18316 5389

Left Gray 111965 82249 71548 30715 24175

White 106326 46698 86126 21749 10415

Right Gray White 113992 114729 89685 51446 88064 68391 19924 30887 14012 5006

Left Gray 111395 77652 75041 35416 17798

White 113429 42071 87945 25602 7590

Figure 6-4

Parcellation of the cerebrum and volume data for male and female subjects 3-5.

[89]


Right Gray White 103524 98169 72454 42692 61790 58773 21719 36907 3567 13464

Left Gray 102647 71393 54473 38339 12115

White 91948 40424 63247 24538 5251

Right Gray White 110389 96916 66418 31062 69192 70197 27048 13355 15019 4380

Left Gray 111351 75639 58868 26864 14501

White 93280 37665 61730 15889 5981

Right Gray White 96793 97578 72653 40173 57404 61460 27864 16251 14362 4091

Gray 99521 68233 57733 29577 11451


Right Gray White 118797 128975 54770 88306 77117 63261 14539 26963 4783 13485

Left Gray 127333 82070 50432 30538 14989

White 139931 46342 57626 21747 7392

Right Gray White 109792 106403 83882 42326 69220 79588 32597 21333 16269 5559

Left Gray 116020 80514 69138 34798 13267

White 108541 39024 79336 24448 5533

Right Gray White 101196 111313 64265 39680 72996 99407 34262 24153 15796 5843

Left Gray 102990 76279 66577 28449 17586

White 110455 49820 88844 21911 8638

-^••^



Left

White 95006 36478 63477 20614 5128

Figure 6-5

Parcellation of the cerebrum and volume data for male and female subjects 6-8. [90]






Right Gray White 99585 87623 74735 36586 59061 60107 16289 29866 3408 13481

Gray 94113 78152 57595 23762 16692

Right Gray White 96613 93635 68715 34701 62196 62305 24149 12047 13174 4490

Gray 96648 71443 54839 24410 15957

Right Gray White 94961 102228 66620 42973 48422 55421 23995 14665 12881 4452

Gray 91653 62781 50920 23878 14039

Left

Left

Left

White 84643 39263 59780 15261 5706

White 89800 36953 55328 14132 7128

White 96670 40809 58919 16133 6546




Right White Gray 120092 107026 44668 73948 82277 62025 20784 30849 5529 13410

Left Gray 103570 79512 62418 24370 14398

White 117836 50970 78276 19370 7959

Right Gray White 106103 103380 83187 45688 64390 75212 28988 16304 15617 4945

Left Gray 105243 82616 67967 26652 14386

White 96829 46027 78625 18078 6333

Right Gray White 94407 113973 43975 69432 82730 58752 27674 31699 5422 13356

Gray 96405 74810 57420 25892 15432

Left

White 112035 46981 80297 23341 8759

Figure 6-6


[91]




Right White Gray 94687 84335 30507 60292 68174 65320 25774 14731 16517 4253

Gray 95024 69904 58344 24570 11142

Right Gray White 90756 91944 67537 36901 55294 63071 25260 15048 12273 4348

Gray 89656 59687 59520 29165 12402

Right Gray White 89799 89803 64719 35843 55167 67358 28855 16040 11756 3322

Gray 86249 66030 52794 27082 15004

Left

Left

Left

White 81583 37697 62278 15417 4632

White 83409 31595 69549 20514 5427

White 87027 36473 62672 17973 6389

Figure 6-7


[92]




Right White Gray 117441 106107 47058 79990 54183 71690 19841 26612 6710 16471

Left Gray 102185 73779 62092 25824 17111

Right Gray White 103786 104071 82889 48384 62273 76965 24181 13864 12352 4393

Left Gray White 101134 104282 76424 43264 58997 73407 31582 21592 15402 7206

Right Gray White 104907 99505 79372 42289 60361 67768 28287 16063 12353 4179

Left Gray 106041 81008 56478 24600 16099

White 109943 40860 73247 22020 9019

White 96821 43296 65929 16452 6531




Left

Right Gray White 85513 93660 60158 32548 48870 60441 31416 21025 16979 5628

Gray 85618 65374 49975 24266 12142

Right Gray White 93574 84679 60731 30269 63480 61391 24506 14049 13089 4232

Gray 90742 63941 60143 21932 17326

Right Gray White 92418 80806 66764 32334 57575 61125 22372 11862 16356 4445

Gray 93907 71282 53923 20984 12168

Left

White 88750 36805 62953 19051 6044

White 79975 33549 61285 15012 7252

Leftwhite White

White White !

79977 36154 55465 11857 5064




Right Gray White 104639 92950 79177 39211 66755 73786 26768 14362 12981 3967

Gray 98837 79913 66823 24180 15055

Right Gray White 92788 102536 44630 73354 54402 73196 20078 28425 3774 10738

Gray 94837 66472 59243 30884 11970

Right Gray White 100599 94659 69858 36351 52786 60893 34741 24089 12104 4462

Gray 96896 77868 58216 23177 16322

Left

Left

Left

White 89565 40138 70555 14526 6821

White 100663 35513 77122 23549 6253

White 93662 42257 64832 17330 6980

Figure 6-8


[93]




Right Gray White 85183 78352 64148 34854 58768 64573 22906 10777 14313 4015

Gray 85737 65656 51573 24128 11651

Right Gray White 84695 80640 62535 33812 53137 57759 20876 9528 14066 4068

Gray 86749 59766 49834 24332 11173

Right Gray White 88651 78612 65132 33563 52041 53863 24379 12226 12082 3421

Gray 89964 62840 53050 20882 9375

Left

Left

Left

White 76785 35529 61241 14310 5409

White 80855 31558 53772 14685 6597

White 79984 33507 498% 11290 4013

Figure 6-9


[94]




Right Gray White 99255 88063 71693 36205 61648 66470 28017 14517 15807 4808

Left Gray 100376 69159 64925 28766 15559

Right Gray White 94495 90140 71856 39676 54354 68812 23631 14106 13872 4568

Gray 90793 74006 60145 20980 13097

Right Gray White 91676 88583 64712 36208 56012 74212 25761 16615 13899 5174

Gray 93344 63665 5291 1 31263 13372

Left

Left

White 86538 32038 64385 16367 6001

White 89489 42616 67255 14344 5048

White 90461 35250 65903 20454 5529




Right White Gray 86260 82421 36797 61638 46564 43663 14223 26564 4162 13229

Gray 83263 59141 41526 28515 13334

Right White Gray 84105 79429 59818 32721 50628 54151 25030 13133 10783 3043

Gray 81525 60058 52812 21164 10929

Right Gray White 82133 78424 61405 33222 46446 53627 23503 12154 11124 3614

Gray 81006 56847 47395 23781 13717

Left

Left

Left

White 80744 35156 47957 19237 5914

White 73833 33078 57115 13162 4412

White 78859 30732 49817 15134 6003



23M 23

Frontal Temporal Parietal Occipital Cingulate

Right Gray White 83259 89690 58720 34309 50715 65215 34112 20140 12737 4472

Gray 86368 61148 52504 30637 12520

Right Gray White 84087 84820 77437 41193 47486 57257 22365 14798 13345 4734

Gray 86240 66731 61096 21058 12915

Right Gray White 85490 83443 65606 37808 49722 62786 25806 16438 9338 2606

Gray 81152 62561 52171 24843 14586

Left

Left

Left

White 87486 34625 67738 19013 5423

White 80119 33771 66723 14912 6462

White 81195 33449 62562 18423 6805

Figure 6-10


[95]


Chapter 7 Sections through Dolicho

D

olicho, the brain described in Chapter 2, is here sliced into several axial, coronal, and parasagittal sequences. The goal is to demonstrate the role played by different incidences of sections in the apparent relations of anatomic structures. To obtain these sections at the desired angle to a set external landmark and at levels that include most structures in posterior and anterior fossae, I relied on the capabilities of Brainvox (Damasio and Frank, 1992; Frank et al., 1997). First, the canto-meatal line, the reference most often used in the alignment of routine magnetic resonance (MR) and computed tomographic (CT) scans, was drawn on both the left and the right; second, a plane that included these two lines was constructed; then, using another Brainvox program, MP-FIT, parallel planes at a distance of 5 mm were constructed so as to encompass the whole brain and posterior fossa contents. The result is the 24 axial sections seen in Figures 7-1 through 7-25. There is a reason to choose a set of cuts parallel to the canto-meatal line for the first sequence, usually designated as "axial" slices or cuts; this is the orientation seen in most axial sequences obtained in standard MR studies, even if it is not exactly the incidence most often used in brain cutting sessions and in most anatomy atlases. The incidence most commonly used for the latter is closer to the inferior orbito-meatal line, which has a rostral angulation of approximately 10° in relation to the canto-meatal line. Of note, that was the incidence chosen in the first edition of this atlas. The next section depicts a series of coronal slices obtained at 90° to the cantomeatal axial slices (Figs. 7-26 to 7-58). Again, this is the incidence most often seen in coronal slices of standard MR sequences, given that the coronal sequence is taken in a plane perpendicular to that of the axial sequence. The individual brain slices are obtained at 5 mm intervals, as everywhere else in this atlas. Often, MR studies are conducted with a rostral angulation, a so-called negative tilt. This is often necessary in older subjects, who may have changes in the cervical spine that do not permit head flexion, and in intubated patients, whose heads must be hyperextended. In those same circumstances, CTs also are obtained with a negative tilt. The incidence of —30° chosen for Figures 7-59 to 7-85 is meant to give an idea of the configuration of the brain sections in such

[97]


[98]

a situation. (This sequence corresponds roughly to the —20° sequence seen in the first edition of this atlas.) Obviously, there is no "standard" negative tilt. The reader should take note of the marked changes in appearance of certain structures when moving from an axial sequence parallel to the canto-meatal line to a sequence obtained with a rostral negative tilt. For instance, observe what happens to the calcarine fissure and to the two main components of the mesial occipital lobe: the infracalcarine region, with the lingual and fusiform gyri, and the supracalcarine sector, with the cuneus. Compare Figures 7-66 through 7-71 with Figures 7-12 through 7-15. The cuts in Figures 7-66 and 7-67 barely slice through the temporal lobe, but they show the most posterior sector of the calcarine fissure in the polar region of the occipital lobe. This same sector of the visual cortex is seen in Figures 7-12 and 7-13. However, in the latter images from the canto-meatal axial sequence, the visual cortex appears in the same cut in which most of the temporal lobes and a middle sector of the frontal lobe can be seen. If we look for the corresponding frontal sector in the hyperextension axial sequence, we find it in Figures 7-76 through 7-79, in which no occipital structures are seen and only frontal and parietal structures are visible. As happened with the canto-meatal axial sequence, the negative tilt series is followed by the corresponding coronal series. This sequence was obtained at 90° from the corresponding axial sequence, which translates into 120° to the cantomeatal line (see Figs. 7-86 to 7-118). Note that here, at the point at which the cuts slice through the beak of the corpus callosum, they also slice through the posterior sector of the temporal pole. In the coronal sequence (corresponding to the axial sequence parallel to the canto-meatal line), this sector of the temporal pole appears only when the slices pass through the body of the callosum, well behind the beak (Figs. 7-37, 7-38). In relation to the frontal operculum, slices 11 and 12 (Figs. 7-37,7-38) cut through its posterior regions, the pars opercularis, and even the lower sector of the precentral gyrus, while in Figures 7-95 and 7-96 cuts 9 and 10 at the level of the beak of the callosum still slice through the pars triangularis, barely touching the anterior sector of the pars opercularis. With respect to the characteristic juncture of the calcarine fissure and the occipitoparietal sulcus (in a ><-like shape) seen in the right hemisphere of cut 26 (Fig. 7-111), note that it coincides with a cut through the posterior region of the paracentral gyrus in the coronal hyperextension sequence. However, in the coronal sections perpendicular to the canto-meatal line (slice 27 in Fig. 7-53), the superior sector of the cut shows the most posterior regions of the cuneus. To see the paracentral gyrus, we need to move back to Figures 7-46 and 7^7 (cuts 20 and 21). The last axial sequence (Figs. 7-119 to 7-144) is a posterior fossa incidence, often used when the posterior fossa is the target region. This sequence was obtained using a caudal rotation of 10° to the canto-meatal plane. Once again, the relationships vary. For example, while the left pars triangularis first appears in Figure 7-128 (when the slice reveals anterior temporal lobe, no occipital lobe or corpus callosum, and mid-sectors of the cerebellum), in the hyperextended axial sequence this same frontal region is visible together with the beak and body of the callosum and the parietal lobe (Fig. 7-77). On the other hand, in the canto-meatal axial sequence, this frontal sector is seen in slices 9 and 10 (Fig. 7-11) along with a large sector of the temporal lobe and the lower sector of the occipital lobe. The parasagittal sequences were also obtained at 90° to the axial sequence. They usually proceed from the left to the right hemisphere, parallel to the in-

terhemispheric fissure. The incidence of the axial sections exerts its influence in the position the section has on the film (more or less tilted posteriorly) but does not interfere with the relative position of the different structures, given that the sequence is always meant to be parallel to the interhemispheric fissure. One parasagittal sequence (Figs. 7-145 to 7-183) is offered in this chapter, starting in the left temporal lobe and proceeding to the right. The sections are also set at 5 mm intervals with the exception of slices 18 and 19, which are separated by 10 mm, 5 mm on each side of the interhemispheric plane. The last sequence in the chapter is again a canto-meatal axial sequence (the same as in Figs. 7-2 through 7-25). Here, the images show the approximate limits of the cytoarchitectonic fields of Brodmann. For the same reasons to which I alluded earlier, MR images, even those with the best resolution, do not allow identification of cytoarchitectonic fields. All we can do is approximate using gyral and sulcal information related to the available data from microscopic studies. As noted, it is reasonable to refer to the pars opercularis of the inferior frontal gyrus as Brodmann's field 44 or to the supramarginal gyrus as area 40; but we must keep in mind that we are simply changing the name we attribute to a macroscopically identifiable sector of the brain, the pars opercularis or the supramarginal gyrus, because it has recognizable macroscopic limits and not commenting on the microscopic characteristics of the region. Brodmann's terminology is used when we designate regions that occupy more than one macroscopically identifiable sector (e.g., area 37 in the temporal lobe). For these reasons and because several readers commented on the lack of cytoarchitectonic field identification in the previous edition of this atlas, I decided to include it here. It will be important, however, to examine this last sequence together with the images that define the gyri because only correct identification of the gyri allows for translation into Brodmann's terminology. In each of the sequences, the image on the left page has the sulci identified and the image on the right page has the gyri and subcortical structures identified. The reader should note that even in images carefully placed at the same level in the right and left hemispheres, the structures appearing on either side are not mirror images of each other. Only the clearly recognizable subcortical structures were labeled. No attempt was made to label likely sites of structures not seen, nor were the several segments of the ventricular system labeled, the main purpose of the atlas being the recognition of cortical structures. The actual MR image of the cut used for anatomic description is shown on the upper and lower outside corners of each page. Note that the MR images and the stripped brain slices in the center are precisely the same. Next to the centerfold, the four views of the brain, right and left, lateral and mesial views, show the setting of the level of the cuts used on that page. All slices are shown in the radiologic convention: right hemisphere on the left, left hemisphere on the right. The first image of each sequence shows the right and left hemispheres, in dorsolateral and mesial views, as seen in Chapter 2, with the gyri colored (Figs. 2-2, 2—4, and 2-6) with a superimposed grid corresponding to the slices to follow. Above is the image of the transparent head with the left hemisphere visible. The canto-meatal line is drawn in red, and a sample of slices is marked to show the angulation of the slices of the section in relation to the canto-meatal line.

Sections through Dolicho

[99]

Canto-meatal Incidence: Axial Slices

[100]

Figure 7-1

Left hemisphere of Dolicho seen through the transparent head on top. The canto-meatal line is marked in red. Black lines represent a sample of the slices obtained parallel to the canto-meatal line. Underneath are the two hemispheres in lateral and mesial

views, as seen in Figures 2-2 and 2-4, with gyri individually colored. The lines correspond to the slices parallel to the cantomeatal line depicted in this section. [101]

Figure 7-2

Slices 1 and 2 parallel to the canto-meatal line in Dolicho. Identification of sulci.

[102]

Figure 7-3

Slices 1 and 2 parallel to the canto-meatal line in Dolicho. Identification of gyri.

[103]

Figure 7-4 Slices 3 and 4 parallel to the canto-meatal line in Dolicho. Identification of sulci.

[104]

Figure 7-5


[105]

Figure 7-6


[106]

Figure 7-7


[107]

Figure 7-8


[108]

Figure 7-9


[109]

Figure 7-10


[110]

Figure 7-11


[111]

Figure 7-12


[112]

Figure 7-13


[113]


[114]

Figure 7-15 Slices 13 and 14 parallel to the canto-meatal line in Dolicho. Identification of gyri.

[115]

Figure 7-16


[116]

Figure 7-17


[117]


[118]

Figure 7-19


[119]

Figure 7-20


[120]

Figure 7-21


[121]

Figure 7-22


[122]

Figure 7-23


[123]

Figure 7-24


[124]

Figure 7-25


[125]

Canto-meatal Incidence: Coronal Slices

[126]

Figure 7-26

Left hemisphere of Dolicho seen through the transparent head on top. The canto-meatal line is marked in red. Black lines represent a sample of slices obtained at 90° to the canto-meatal line, which is the coronal incidence when the axial slices are obtained

parallel to the canto-meatal line. Underneath are the two hemispheres in lateral and mesial views, as seen in Figures 2-2 and 2-4, with gyri individually colored. Lines correspond to slices obtained at 90° to the canto-meatal line as depicted in this section.

[127]

Figure 7-27

Slices 1 and 2 at 90° to the canto-meatal line in Dolicho. Identification of sulci.

[128]

Figure 7-28

Slices 1 and 2 at 90° to the canto-meatal line in Dolicho. Identification of gyri.

[129]

Figure 7-29


[130]

Figure 7-30


[131]

Figure 7-31


[132]

Figure 7-32


[133]

Figure 7-33


[134]

Figure 7-34


[135]

Figure 7-35


[136]

Figure 7-36


[137]

Figure 7-37


[138]

Figure 7-38


[139]

Figure 7-39


[140]

Figure 7-40


[141]

Figure 7-41 Slices 15 and 16 at 90° to the canto-meatal line in Dolicho. Identification of sulci.

[142]

Figure 7-42


[143]

Figure 7-43


[144]

Figure 7-44


[145]

Figure 7-45 Slices 19 and 20 at 90° to the canto-meatal line in Dolicho. Identification of sulci.

[146]

Figure 7-46


[147]

Figure 7-47


[148]

Figure 7-48


[149]

Figure 7-49


[150]

Figure 7-50


[151]

Figure 7-51


[152]

Figure 7-52


[153]

Figure 7-53


[154]

Figure 7-54


[155]

Figure 7-55


[156]

Figure 7-56


[157]

Figure 7-57

Slices 31, 32, and 33 at 90° to the canto-meatal line in Dolicho. Identification of sulci.

[158]

Figure 7-58

Slices 31, 32, and 33 at 90° to the canto-meatal line in Dolicho. Identification of gyri.

[159]

Hyperextension Incidence: Axial Slices

[160]

Figure 7-59

Left hemisphere of Dolicho seen through the transparent head on top. The canto-meatal line is marked in red. Black lines represent a sample of slices obtained at -30° to the canto-meatal line, which is the incidence found with a hyperextended head.

Underneath are the two hemispheres in lateral and mesial views, as seen in Figures 2-2 and 2-4, with gyri individually colored. Lines correspond to slices obtained at —30° to the canto-meatal line as depicted in this section.

[161]

Figure 7-60

Slices 1 and 2 at —30° to the canto-meatal line in Dolicho. Identification of sulci.

[162]

Figure 7-61

Slices 1 and 2 at —30° to the canto-meatal line in Dolicho. Identification of gyri.

[163]

Figure 7-62


[164]

Figure 7-63 Slices 3 and 4 at —30° to the canto-meatal line in Dolicho. Identification of gyri.

[165]

Figure 7-64


[166]


[167]

Figure 7-66


[168]

Figure 7-67


[169]

Figure 7-68


[170]


[171]

Figure 7-70


[172]


[173]

Figure 7-72


[174]

Figure 7-73


[175]

Figure 7-74


[176]


[177]

Figure 7-76


[178]

Figure 7-77

Slices 17 and 18 at -30° to the canto-meatal line in Dolicho. Identification of gyri.

[179]

Figure 7-78

Slices 19 and 20 at -30° to the canto-meatal line in Dolicho. Identification of sulci.

[180]

Figure 7-79


[181]

Figure 7-80 Slices 21 and 22 at —30° to the canto-meatal line in Dolicho. Identification of sulci.

[182]

Figure 7-81


[183]

Figure 7-82


[184]

Figure 7-83


[185]

Figure 7-84 Slices 25, 26, and 27 at -30° to the canto-meatal line in Dolicho. Identification of sulci.

[186]

Figure 7-85

Slices 25,26, and 27 at —30° to the canto-meatal line in Dolicho. Identification of gyri.

[187]

Hyperextension Incidence: Coronal Slices

[188]

Figure 7-86

Left hemisphere of Dolicho seen through the transparent head on top. The canto-meatal line is marked in red. Black lines represent a sample of slices obtained at +60° to the canto-meatal line, which is the coronal incidence when the axial slices are obtained

with a hyperextended head. Underneath are the two hemispheres in lateral and mesial views as seen in Figures 2-2 and 2-4, with gyri individually colored. Lines correspond to slices obtained at +60° to the canto-meatal line as depicted in this section.

[189]

Figure 7-87

Slices 1 and 2 at +60° to the canto-meatal line in Dolicho. Identification of sulci.

[190]

Figure 7-88

Slices 1 and 2 at +60° to the canto-meatal line in Dolicho. Identification of gyri.

[191]

Figure 7-89 Slices 3 and 4 at +60° to the canto-meatal line in Dolicho. Identification of sulci.

[192]

Figure 7-90


[193]

Figure 7-91


[194]

Figure 7-92


[195]


[196]

Figure 7-94


[197]


[198]

Figure 7-96


[199]

Figure 7-97


[200]

Figure 7-98 Slices 11 and 12 at +60° to the canto-meatal line in Dolicho. Identification of gyri.

[201]

Figure 7-99


[202]


[203]


[204]

Figure 7-102


[205]

Figure 7-103


[206]

Figure 7-104


[207]

Figure 7-105


[208]


[209]

Figure 7-107


[210]

Figure 7-108


[211]

Figure 7-109


[212]


[213]

Figure 7-111


[214]

Figure 7-112


[215]

Figure 7-113


[216]


[217]

Figure 7-115


[218]


[219]


[220]

Figure 7-118


[221]

Posterior Fossa Incidence: Axial Slices

[222]

Figure 7-119 Left hemisphere of Dolicho seen through the transparent head on top. The canto-meatal line is marked in red. Black lines represent a sample of slices obtained at +10° to the canto-meatal line, which is the incidence of axial slices when posterior fossa

structures are the target. Underneath are the two hemispheres in lateral and mesial views, as seen in Figures 2-2 and 2-4, with gyri individually colored. Lines correspond to slices obtained at +10° to the canto-meatal line as depicted in this section.

[223]

Figure 7-120


[224]

Figure 7-121


[225]

Figure 7-122


[226]


[227]

Figure 7-124


[228]

Figure 7-125


[229]

Figure 7-126


[230]

Figure 7-127


[231]

Figure 7-128


[232]

Figure 7-129


[233]

Figure 7-130


[234]

Figure 7-131


[235]

Figure 7-132


[236]

Figure 7-133


[237]

Figure 7-134


[238]

Figure 7-135


[239]

Figure 7-136


[240]

Figure 7-137


[241]

Figure 7-138


[242]

Figure 7-139


[243]

Figure 7-140


[244]

Figure 7-141


[245]

Figure 7-142

Slices 23, 24, and 25 at +10° to the canto-meatal line in Dolicho. Identification of sulci.

[246]

Figure 7-143

Slices 23, 24, and 25 at +10° to the canto-meatal line in Dolicho. Identification of gyri.

[247]

Parasagittal Incidence

[248]

Figure 7-144

Dolicho seen from the back and front (top) and from the top and bottom (below), as in Figure 2-6. Black lines represent slices

obtained parallel to the interhemispheric fissure depicted in this section. They begin at the outer surface of the left hemisphere.

[249]

Figure 7-145

Left hemisphere parasagittal slices 1 and 2 in Dolicho. Identification of sulci.

[250]

Figure 7-146

Left hemisphere parasagittal slices 1 and 2 in Dolicho. Identification of gyri.

[251]

Figure 7-147


[252]

Figure 7-148


[253]

Figure 7-149


[254]

Figure 7-150


[255]

Figure 7-151


[256]

Figure 7-152


[257]

Figure 7-153


[258]

Figure 7-154


[259]

Figure 7-155 Left hemisphere parasagittal slices 11 and 12 in Dolicho. Identification of sulci.

[260]

Figure 7-156


[261]

Figure 7-157


[262]

Figure 7-158 Left hemisphere parasagittal slices 13 and 14 in Dolicho. Identification of gyri.

[263]

Figure 7-159


[264]

Figure 7-160 Left hemisphere parasagittal slices 15 and 16 in Dolicho. Identification of gyri.

[265]

Figure 7-161 Left hemisphere parasagittal slices 17 and 18 in Dolicho. Identification of sulci.

[266]

Figure 7-162


[267]

Figure 7-163

Right hemisphere parasagittal slices 19 and 20 in Dolicho. Identification of sulci.

[268]

Figu re 7-16 4 Right hemisphere parasagittal slices 19 and 20 in Dolicho. Identification of gyri.

[269]

Figure 7-165


[270]

Figure 7-166 Right hemisphere parasagittal slices 21 and 22 in Dolicho. Identification of gyri.

[271]

Figure 7-167


[272]

Figure 7-168

Right hemisphere parasagittal slices 23 and 24 in Dolicho. Identification of gyri.

[273]

Figure 7-169


[274]

Figure 7-170


[275]

Figure 7-171


[276]

Figure 7-172


[277]

Figure 7-173


[278]

Figure 7-174


[279]

Figure 7-175


[280]

Figure 7-176


[281]

Figure 7-177


[282]

Figure 7-178


[283]

Figure 7-179


[284]

Figure 7-180


[285]

Brodmann's Fields

[286]

Figure 7-181

Right and left hemispheres of Dolicho in mesial and lateral views with the gyri colored and Brodmann's cytoarchitectonic fields marked, as in Figures 2-7 and 2-8. Black lines correspond to

axial slices obtained parallel to the canto-meatal line, as in Figure 7-1, corresponding to the slices depicted in this section.

[287]

Figure 7-182

Slices 1-6 parallel to the canto-meatal line with Brodmann's fields in Dolicho.

[288]

Figure 7-183

Slices 7-12 parallel to the canto-meatal line with Brodmann's fields marked in Dolicho.

[289]

Figure 7-184


[290]

Figure 7-185


[291]


Chapter 8 Sections through Brachi-1

T

he main goal of this chapter is to show that, in different individuals, axial sequences obtained with the same incidences can produce different images. The procedures are the same used for Dolicho. The two most typical sequences used in magnetic resonance (MR) and computed tomographic studies are shown: parallel to the canto-meatal line (Figs. 8-1 to 8-25) and the 30-degree rostral angulation sequence obtained with the hyperextended head (Figs. 8-57 to 8-81). As in the previous chapter, a set of coronal sections to each of the axial sequences is also shown (Figs. 8-26 to 8-56 and 8-82 to 8-110). The posterior fossa incidence with a caudal 10° tilt is shown in Figures 8-111 to 8-135. Again, sulci are marked on the lefthand side and gyri, on the right. The MR cuts from which the images were obtained and the levels of the cuts are depicted as in Chapter 7. The first image of each sequence shows, as in Chapter 7, the two hemispheres seen from the dorsolateral and mesial views, with a superimposed grid corresponding to the slices to follow. The brain images used here are the same as those in Figures 3-2, 3-4, and 3-6. Above is the image of the transparent head and the left hemisphere of Brachi1, with the canto-meatal line drawn in red and a sample of the slices in the section. The comments made in Chapter 7 apply here too: the relative appearance among the different structures depends on the incidence of the cut. The reader should compare the slices in one sequence to those in the others. It is also important to compare the images seen in this chapter to those obtained with the same incidence in Chapter 7. See, for instance, the first axial incidence in these two chapters, parallel to the canto-meatal line. Compare the slices that first show the calcarine fissure, slice 10 in Figures 8-10 and 8-11 and slice 11 in Figures 7-12 and 7-13. There is a different overall configuration of the slice (Brachi-1 is rounder than Dolicho) but also considerable similarity in the visible structures, particularly in the frontal and temporal lobes. The structures in the occipital lobe, however, are quite different. Slice 10 in this chapter barely touches the occipital lobe, while the corresponding cut in Chapter 7 (slice 11 in Figs. 7-12, 7-13) almost reaches the cuneus (which is visible in slice 12). In Brachi-1, we must advance to slice 13 (Fig. 8-15) to catch the very first sliver of the cuneus.

[293]


[294]

Figure 8-1

Left hemisphere of Brachi-1 seen through the transparent head on top. The canto-meatal line is marked in red. Black lines represent a sample of slices obtained parallel to the canto-meatal line. Underneath are the two hemispheres in lateral and mesial

views, as seen in Figures 3-2 and 3-4, with gyri individually colored. Lines correspond to slices parallel to the canto-meatal line as depicted in this section.

[295]

Figure 8-2

Slices 1 and 2 parallel to the canto-meatal line in Brachi-1. Identification of sulci.

[296]

Figure 8-3

Slices 1 and 2 parallel to the canto-meatal line in Brachi-1. Identification of gyri.

[297]

Figure 8-4


[298]

Figure 8-5


[299]

Figure 8-6 Slices 5 and 6 parallel to the canto-meatal line in Brachi-1. Identification of sulci.

[300]

Figure 8-7


[301]


[302]

Figure 8-9


[303]


[304]

Figure 8-11


[305]


[306]

Figure 8-13


[307]

Figure 8-14


[308]

Figure 8-15


[309]

Figure 8-16


[310]

Figure 8-17


[311]


[312]

Figure 8-19 Slices 17 and 18 parallel to the canto-meatal line in Brachi-1. Identification of gyri.

[3131


[314]

Figure 8-21


[315]

Figure 8-22


[316]

Figure 8-23


[317]

Figure 8-24


[318]


[319]

Canto-meatal Incidence: Coronal Slices

[320]

Figure 8-26

Left hemisphere of Brachi-1 seen through the transparent head on top. The canto-meatal line is marked in red. Black lines represent a sample of slices obtained at 90° to the canto-meatal line, which is the coronal incidence when the axial slices are obtained

parallel to the canto-meatal line. Underneath are the two hemispheres in lateral and mesial views, as seen in Figures 3-2 and 3-4, with gyri individually colored. Lines correspond to slices obtained at 90° to the canto-meatal line as depicted in this section. [321]

Figure 8-27 Slices 1 and 2 at 90° to the canto-meatal line in Brachi-1. Identification of sulci.

[322]

Figure 8-28 Slices 1 and 2 at 90° to the canto-meatal line in Brachi-1. Identification of gyri.

[3231

Figure 8-29

Slices 3 and 4 at 90° to the canto-meatal line in Brachi-1. Identification of sulci.

[324]

Figure 8-30

Slices 3 and 4 at 90° to the canto-meatal line in Brachi-1. Identification of gyri.

[325]

Figure 8-31


[326]

Figure 8-32


[327]

Figure 8-33


[328]

Figure 8-34


[329]

Figure 8-35


[330]

Figure 8-36


[331]

Figure 8-37


[332]

Figure 8-38


[333]

Figure 8-39


[334]

Figure 8-40


[335]


[336]

Figure 8-42


[337]

Figure 8-43


[338]

Figure 8-44


[339]

Figure 8-45


[340]

Figure 8-46


[341]

Figure 8-47


[342]

Figure 8-48


[343]

Figure 8-49


[344]

Figure 8-50


[345]

Figure 8-51


[346]

Figure 8-52


[347]


[348]

Figure 8-54


[349]

Figure 8-55


[350]

Figure 8-56


[351]


[352]

Figure 8-57

Left hemisphere of Brachi-1 seen through the transparent head on top. The canto-meatal line is marked in red. Black lines represent a sample of slices obtained at —30° to the canto-meatal line, which is the incidence found with a hyperextended head.

Underneath are the two hemispheres in lateral and mesial views, as seen in Figures 3—2 and 3-4, with gyri individually colored. Lines correspond to slices obtained at —30° to the canto-meatal line as depicted hi this section.

[353]

Figure 8-58

Slices 1, 2, 3, and 4 at —30° to the canto-meatal line in Brachi1. Identification of sulci.

[354]

Figure 8-59

Slices 1, 2, 3, and 4 at —30° to the canto-meatal line in Brachi1. Identification of gyri.

[355]

Figure 8-60 Slices 5 and 6 at —30° to the canto-meatal line in Brachi-1. Identification of sulci.

[356]

Figure 8-61

Slices 5 and 6 at —30° to the canto-meatal line in Brachi-1. Identification of gyri.

[357]

Figure 8-62

Slices 7 and 8 at —30° to the canto-meatal line in Brachi-1. Identification of sulci.

[358]

Figure 8-63 Slices 7 and 8 at —30° to the canto-meatal line in Brachi-1. Identification of gyri.

[359]

Figure 8-64 Slices 9 and 10 at — 30° to the canto-meatal line in Brachi-1. Identification of sulci.

[360]

Figure 8-65


[361]


[362]


[363]

Figure 8-68


[364]

Figure 8-69 Slices 13 and 14 at -30° to the canto-meatal line in Brachi-1. Identification of gyri.

[365]

Figure 8-70


[366]

Figure 8-71


[3671

Figure 8-72

Slices 17 and 18 at -30° to the canto-meatal line in Brachi-1. Identification of sulci.

[368]


[369]


[370]

Figure 8-75

Slices 19 and 20 at -30° to the canto-meatal line in Brachi-1. Identification of gyri.

[371]

Figure 8-76


[372]

Figure 8-77


[373]

Figure 8-78


[374]

Figure 8-79


[375]

Figure 8-80

Slices 25, 26 and 27 at —30° to the canto-meatal line in Brachi1. Identification of sulci.

[376]

Figure 8-81

Slices 25, 26 and 27 at -30° to the canto-meatal line in Brachi1. Identification of gyri.

[3771

Hyperextension Incidence: Coronal Slices

[378]

Figure 8-82

Left hemisphere of Brachi-1 seen through the transparent head on top. The canto-meatal line is marked in red. Black lines represent a sample of slices obtained at +60° to the canto-meatal line, which is the coronal incidence when the axial slices are obtained

with a hyperextended head. Underneath are the two hemispheres in lateral and mesial views, as seen in Figures 3-2 and 3-4, with gyri individually colored. Lines correspond to slices obtained at +60° to the canto-meatal line as depicted in this section.

[379]

Figure 8-83

Slices 1 and 2 at +60° to the canto-meatal line in Brachi-1. Identification of sulci.

[380]

Figure 8-84

Slices 1 and 2 at +60° to the canto-meatal line in Brachi-1. Identification of gyri.

[381]

Figure 8-85 Slices 3 and 4 at +60° to the canto-meatal line in Brachi-1. Identification of sulci.

[382]

Figure 8-86


[383]

Figure 8-87


[384]

Figure 8-88


[385]

Figure 8-89


[386]

Figure 8-90


[387]

Figure 8-91


[388]

Figure 8-92


F3891

Figure 8-93


[390]

Figure 8-94


[391]

Figure 8-95


[392]

Figure 8-96 Slices 13 and 14 at +60° to the canto-meatal line in Brachi-1. Identification of gyri.

[393]


[394]

Figure 8-98


[395]

Figure 8-99


[396]

Figure 8-100


[397]


[398]

Figure 8-102


[399]

Figure 8-103


[400]

Figure 8-104


[401]

Figure 8-105


[402]

Figure 8-106


f4031


[404]

Figure 8-108


[405]

Figure 8-109 Slices 27, 28, and 29 at +60° to the canto-meatal line in Brachi1. Identification of sulci.

[406]

Figure 8-110 Slices 27, 28, and 29 at +60° to the canto-meatal line in Brachi1. Identification of gyri.

[407]


[408]

Figure 8-111

Left hemisphere of Brachi-1 seen through the transparent head on top. The canto-meatal line is marked in red. Black lines represent a sample of slices obtained at +10° to the cantomeatal line, which is the incidence of axial slices obtained when posterior

fossa structures are the target. Underneath are the two hemispheres in lateral and mesial views, as seen in Figures 3-2 and 3-4, with gyri individually colored. Lines correspond to slices obtained at +10° to the canto-meatal line as depicted in this section.

[409]

Figure 8-112


[410]


[411]


[412]


[413]


[414]

Figure 8-117


[415]


[416]


[417]


[418]

Figure 8-121


[419]

Figure 8-122


[420]


[421]

Figure 8-124


[422]


[423]

Figure 8-126


[424]


[425]

Figure 8-128


[426]

Figure 8-129


[427]

Figure 8-130


[428]


[429]

Figure 8-132


[430]

Figure 8-133


[431]

Figure 8-134


[432]

Figure 8-135


[433]


Chapter 9 Sections through Brachi-2

T

he three axial sequences used in the previous two chapters were obtained in Brachi-2. This chapter illustrates how incidences chosen in relation to external landmarks reveal remarkably different structures in subjects with different cranial configurations. Let us continue with the example chosen for the previous chapter, namely, the comparison among slices parallel to the cantomeatal line. Once again, compare the slices in which the calcarine sulcus first appears (Figs. 9-12, 9-13 and Figs. 7-12, 7-13 and 8-10, 8-11). In Figs. 9-12 and 9-13, slice 11, the most anterior segment of the calcarine sulcus, shows up for the first time. This slice shows the corpus callosum anteriorly, sliced at the very top of the beak of the callosum, together with the superior regions of the frontal operculum. On the other hand, in Dolicho (Figs. 7-12, 7-13), the callosum is cut in the middle of the beak and the frontal operculum is sliced through the middle portion rather than through its superior sector. We must advance to Figure 7-17 (slice 16) to see the superior regions of the pars opercularis. In fact, in Brachi-2, slices 11 and 12 of the axial sequence parallel to the canto-meatal line are much closer to slices 11 and 12 in Figure 7-132, the posterior fossa incidence for Dolicho. As in the two preceding chapters, sulci are marked on the left page and gyri, on the right. The magnetic resonance images from which the anatomic images were obtained and the levels of the cuts are as in Chapter 7. The gyri images used to illustrate the setting of the slices in each sequence are those used in Chapter 4 (Figs. 4-2, 4-4, and 4-6).

[435]


[436]

Figure 9-1 Left hemisphere of Brachi-2 seen through the transparent head on top. The canto-meatal line is marked in red. Black lines represent a sample of slices obtained parallel to the canto-meatal line. Underneath are the two hemispheres in lateral and mesial

views, as seen in Figures 4-2 and 4-4, with gyri individually colored. Lines correspond to slices parallel to the canto-meatal line as depicted in this section.

[437]

Figure 9-2


[438]


[439]

Figure 9-4


[440]


[441]


[442]

Figure 9-7


[443]

Figure 9-8


[444]

Figure 9-9


[445]

Figure 9-10


[446]

Figure 9-11


[447]


[448]

Figure 9-13


[449]

Figure 9-14


[450]

Figure 9-15


[451]


[452]


[453]


[454]


[455]

Figure 9-20


[456]

Figure 9-21


[457]

Figure 9-22


[458]

Figure 9-23


[459]

Figure 9-24


[460]

Figure 9-25


[461]


[462]

Figure 9-26

Left hemisphere of Brachi-2 seen through the transparent head on top. The canto-meatal line is marked in red. Black lines represent a sample of slices obtained at —30° to the canto-meatal line, which is the incidence found with a hyperextended head.

Underneath are the two hemispheres in lateral and mesial views, as seen in Figures 4-2 and 4-4, with gyri individually colored. Lines correspond to slices obtained at -30° to the canto-meatal line as depicted in this section. [463]

Figure 9-27

Slices 1, 2, 3, and 4 at —30° to the canto-meatal line in Brachi2. Identification of sulci.

[464]

Figure 9-28

Slices 1, 2, 3, and 4 at -30° at +60° to the canto-meatal line in Brachi-2. Identification of gyri.

[4651


[466]

Figure 9-30


F4671

Figure 9-31


[468]

Figure 9-32


[469]

Figure 9-33


[470]

Figure 9-34


[471]

Figure 9-35


[472]

Figure 9-36


[473]

Figure 9-37


[474]


[475]

Figure 9-39


[476]


[477]

Figure 9-41


[478]

Figure 9-42


[479]


[480]

Figure 9-44


[481]

Figure 9-45 Slices 21 and 22 at -30° to the canto-meatal line in Brachi-2. Identification of sulci.

[482]

Figure 9-46


[483]

Figure 9-47

Slices 23 and 24 at -30° to the canto-meatal line in Brachi-2. Identification of sulci.

[484]


[485]

Figure 9-49

Slices 25, 26, and 27 at —30° to the canto-meatal line in Brachi2. Identification of sulci.

[486]

Figure 9-50

Slices 25, 26, and 27 at —30° to the canto-meatal line in Brachi2. Identification of gyri.

[487]


[488]

Figure 9-51 Left hemisphere of Brachi-2 seen through the transparent head on top. The canto-meatal line is marked in red. Black lines represent a sample of slices obtained at + 10° to the canto-meatal line, which is the incidence of axial slices obtained when poste-

rior fossa structures are the target. Underneath are the two hemispheres in lateral and mesial views, as seen in Figures 4-2 and 4-4, with gyri individually colored. Lines correspond to slices obtained at + 10° to the canto-meatal line as depicted in this section.

[489]

Figure 9-52


[490]

Figure 9-53


[491]

Figure 9-54


[492]

Figure 9-55


[493]


[494]

Figure 9-57


[495]


[496]

Figure 9-59


[497]


[498]


[499]

Figure 9-62


[500]

Figure 9-63


[501]

Figure 9-64


[502]

Figure 9-65


[503]


[504]

Figure 9-67


[505]

Figure 9-68


[506]

Figure 9-69


[507]

Figure 9-70

Slices 19 and 20 at +10° to the canto-meata! line in Brachi-2. Identification of sulci.

[508]


[509]


[510]


[511]

Figure 9-74


[512]

Figure 9-75


[513]


Chapter 10 Application to Lesion Studies

T

his chapter aims at demonstrating how variability due to different incidences of cut can play a role in the determination of lesion location. I use four examples of relatively circumscribed lesions in distinct locations: left parietal, left calcarine, right temporal, and left frontal. All lesions resulted from stroke. Two or more incidences of sections are given for each case to make the point that quick inspection is unlikely to yield a correct reading. Also shown are a transparent head and the appropriate hemisphere with lines marking the slices. The sulci most relevant for a correct interpretation of the lesion location are identified.

[515]


Figures 10-1 and 10-2 show a left parietal infarct seen from the left, through a transparent head, in slices parallel to the canto-meatal line (Fig. 10-1 A) and the corresponding coronal slices (Fig. 10-2A). Figures 10-15 and 10-25 show the sort of axial and coronal slices that would be revealed if the head had been hyperextended. The images obtained parallel to the canto-meatal line and perpendicular to it would probably be interpreted as showing damage in the left parietal lobe (in the inferior parietal lobule, mostly in the supramarginal gyrus). By contrast, the images obtained with a negative rostral tilt—the "hyperextension images" (Fig. 10—15)—could easily be misinterpreted as showing damage in the posterior temporo-occipital region, possibly extending into the angular gyrus. An erroneous reading would arise from the relation of the lesion to the posterior region of the lateral ventricle (at a point at which the frontal lobe barely shows up anteriorly). Observation of the coronal slices (Fig. 10-25) might dispel the erroneous reading given that the lesion is located very high in each cut. However, the fact that it is seen in a coronal slice behind the splenium of the corpus callosum and at the posterior end of the cerebellum and beyond might still suggest that it was located in the occipital lobe. Two clues should help the reader reach the correct interpretation. First, cuts 1 and 2 show the very anterior end of the calcarine fissure, prior to it being joined by the occipitoparietal sulcus (the juncture occurs only in cut 3; from that point on, the sulcus that is seen mesially is the occipitoparietal sulcus, with the calcarine fissure disappearing inferiorly). Second, the intraparietal sulcus appears in cut 5. This reveals that the lesion is lateral to this sulcus and therefore not in the occipital lobe but rather in the parietal.

A Left Parietal Lesion (Figs. 10-1, 10-2)

[517]

Figure 10-1 Two axial incidences in the brain of a 53-year-old, fully righthanded woman with a left parietal infarct. The lesion is seen through the transparent head on the surface of the left hemisphere in the three-dimensionally reconstructed brain. The canto-meatal line is drawn as a dotted line. The position of the

slices (seen on the right) is marked with solid lines. The most important sulci needed to localize the lesion are identified and marked. (A) Slices obtained parallel to the canto-meatal line. (B) Slices obtained in hyperextension.

Figure 10-2 Coronal slices corresponding to the axial slices seen in Figure 10-1.

[519]


As in the previous example, I chose two axial orientations—parallel to the cantomeatal line (Fig. 10-3A) and with a negative rostral tilt (Fig. 10-35)—along with their corresponding coronal cuts (Figs. 10-4A, 10-45) and the mesial view of the left hemisphere (seen through a transparent head from the right). When we examine the axial cuts, regardless of the incidence, there is no doubt that the lesion is in the calcarine region. However, if we begin by inspecting Figure 10-35, it would be possible to read these images as if the lesion were placed more anteriorly in the occipital lobe. It would even be possible to think about a mesial temporo-occipital location rather then a purely occipital one. Inspection of the coronal slices in either panel A or B of Figure 10-4 should leave no doubt that the lesion does involve the calcarine fissure in its anterior sector. At some point, regardless of the angulation to the canto-meatal line, coronal slices will show the joining of the calcarine fissure and the occipitoparietal sulcus in a characteristic shape (><), in which the upper arms of the V shapes (><) corresponds to the occipitoparietal sulcus and the lower to the calcarine fissure (slices 1 and 2 in A, slices 3 and 4 in 5). Inspection of these images shows that the damage involves the lower arm of the left side, the calcarine fissure, and that it does so at the juncture of the two and farther back.

A Left Calcarine Lesion (Figs. 10-3, 10-4)

[521]

Figure 10-3 Two axial incidences in the brain of a 42-year-old, fully righthanded man with a left calcarine infarct. The lesion is seen through the transparent head on the mesial surface of the left hemisphere in the three-dimensionally reconstructed brain. The canto-meatal line is drawn as a dotted line. The position of the

slices (seen on the right) is marked with solid lines. The most important sulci needed to localize the lesion are identified and marked. (A) Slices obtained parallel to the canto-meatal line. (B) Slices obtained in hyperextension.

Figure 10-4 Coronal slices corresponding to the axial slices seen in Figure 10-3.

[523]


Figures 10-5 and 10-6 show a right posterior temporal lobe lesion seen through a transparent head from the right. Figure 10—5 shows the axial slices parallel to the canto-meatal line (A) and the corresponding coronal slices (B). The interpretation of these images is straightforward because the incidence is close to that of images in traditional anatomic atlases. The position of the lesion in A cannot possibly be interpreted as anything but the posterior temporal region. The lesion is at the edge of the temporal lobe, behind the superior temporal sulcus, next to the cerebellum, and behind a very anterior image of the hippocampus; the amygdalae are still visible, and the anterior cingulate begins to be revealed. The subsequent two slices simply confirm the first impression. The coronal slices in Figure 10-55, showing the lesion at the level of the splenium and tail end of the hippocampus (slices 1 and 2) just below the trigone (slices 2 and 3), do not leave much doubt about the location of the lesion. On the other hand Figure 10-6 may raise questions. In Figure 10-6A, I show three slices of a posterior fossa incidence. In spite of the fact that the lesion is seen in slices that cut the frontal lobe relatively high up, above the beak of the corpus callosum, the interpretation is not difficult. The lack of ambiguity is due, once again, to the recognizable sylvian fissure, superior temporal sulcus, and hippocampus. Visualization of the cerebellum also helps: the amount of cerebellum seen along with the obviously high cut through the frontal lobe indicate that the slice was obtained with a posterior fossa incidence. The interpretation would be less clear if the lesion were placed in the parietal lobe (see the higher cuts in the posterior fossa sequences in Chapters 7-9). In Figure 10-65, however, it would be more difficulty to decide where in the temporal lobe the lesion is located. The negative rostral tilt (hyperextension incidence) may suggest that all we see in these slices is a long longitudinal cut through the temporal lobe, perhaps with some occipital structures appearing at the tail end of the slice. This erroneous reading would make one assume that the lesion is in the anterior temporal lobe, just behind the temporal pole. However, as we have seen, this is not the case. The non-canonical presentation of the temporal and occipital structures would lead to a misinterpretation. A correct reading depends on recognizing the following: (1) that slice 3 shows the amygdalae and the hippocampus in a long longitudinal sequence, (2) that in this same slice only the very top of the cerebellar vermis is seen, and (3) that not even a hint of frontal lobe is seen. These features tell us that these slices were obtained with a negative rostral tilt, thus revealing the occipital lobe even in slice 1.

A Right Temporal Lesion (Figs. 10-5, 10-6)

[525]

Figure 10-5

Axial and coronal slices in the brain of a 31-year-old, fully righthanded woman with a right posterior temporal infarct. The lesion is seen through the transparent head on the surface of the right hemisphere in the three-dimensionally reconstructed brain. The canto-meatal line is drawn as a dotted line. The position of

the slices (seen on the right] is marked with solid lines. The most important sulci needed to localize the lesion are identified and marked. (A) Slices obtained parallel to the canto-meatal line. (B) Corresponding coronal slices.

Figure 10-6

Two sets of axial slices in the same brain seen in Figure 10-5. (A) Slices obtained with a posterior fossa incidence. (B) Slices obtained in hyperextension. [527]


Figures 10-7 and 10-8 show the surface projection of a left subcortical frontal lesion seen through a transparent head on the left hemisphere as a faint gray shadow. The lesion was traced in Brainvox and would not have been visible from mere inspection of the lateral surface of the hemisphere. Figure 10—7 shows the coronal slices (A) in which the scan was obtained and which correspond to axial cuts (B) obtained parallel to the inferior orbitomeatal line rather than the canto-meatal line, a rostral —10° tilt from the latter. In these slices, after the sulci in the left hemisphere have been identified, it becomes apparent that the lesion is in the white matter beneath the precentral gyrus, at the level of the inferior frontal sulcus. In Figure 10-8A, we see two slices obtained in hyperextension and, in B, slices obtained with a posterior fossa incidence. Without the help of a threedimensionally reconstructed brain, it is difficult to identify the sulci. One might be tempted to think that in A the lesion is in the parietal lobe and in B it might be in the anterior frontal region. Comparison of the images in A with those in Figures 8-75 and 8-76 or 9-43 and of the images in B with Figures 8-122 and 9-62 of the previous chapters would help to reach the correct interpretation better than a comparison with the corresponding images in Chapter 7. Even so, unequivocal identification of sulci would be best achieved with the help of a three-dimensional image and transfer of such identification onto the twodimensional slices, as demonstrated here.

A Left Frontal Lesion (Subcortical) (Figs. 10-7, 10-8)

[529]

Figure 10-7 Coronal and axial slices in the brain of a 41-year-old, fully righthanded woman with a left subcortical frontal infarct. The lesion is projected onto the surface of the left hemisphere in the threedimensionally reconstructed brain seen through the transparent head. The canto-meatal line is drawn as a dotted line. The position of the slices (seen on the right) is marked with solid lines.

[530]

The most important sulci needed to localize the lesion are identified and marked. (A) Coronal slices obtained during the native magnetic resonance acquisition, which is perpendicular to the axial slices (£), obtained parallel to the inferior orbito-meatal line, a rostral 10° to the canto-meatal line.

Figure 10-8

Two sets of axial slices in the same brain seen in Figure 10-7. (A) Axial slices obtained in hyperextension. (B) Axial slices obtained in a posterior fossa incidence.

[531]


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Index of Anatomical Structures Seen in the Figures

All pages in which a given structure appears in Chapters 1-4, 6, and 10 are noted. The structures that appear in Chapter 5 are noted as 50-75. For structures that appear in Chapters 7-9 only the first page in which they appear, in each sequence, is noted. The exception is the parasagital sequence in Chapter 7 in which the first appearance of structure is noted both for the left and the right hemispheres. Amygdala (a), 109, 141, 173, 201, 229, 261, 273, 301, 335, 363, 391, 415, 443, 473, 495, 526, 527 Anterior commisure (ac), 21, 35, 43, 111, 141, 177, 203, 305, 335, 391 Anterior occipital sulcus (AOS), 18, 22, 32, 36, 40, 44, 50-75, 108, 152, 166, 212, 234, 252, 278, 302, 344, 358, 400, 418, 448, 468, 500, 526, 527 Calcarine fissure (CalcF), 8, 20, 22, 34, 36, 42, 44, 50-75, 112, 148, 166, 210, 234, 262, 268, 304, 342, 360, 398, 420, 446, 468, 500, 519, 522, 523 Caudate nucleus body of caudate nucleus (be), 117, 141, 203, 237, 263, 271, 307, 335, 369, 393, 421, 449, 479, 501 head of caudate nucleus (he), 111, 137, 177, 199, 231, 263, 271, 303, 331, 365, 389, 417, 447, 475, 497 tail of caudate nucleus (tc), 113, 174, 209, 239, 263, 273, 305, 339, 399, 419, 479 Central sulcus (CS), 8, 18, 20, 22, 32, 34, 36, 40, 42, 44, 50-75, 87, 114, 138, 178, 202, 234, 250, 268, 306, 334, 368, 392, 420, 448, 476, 498, 518, 519, 530, 531 Cerebellum cerebellar hemispheres (cerebH), 19, 21, 23, 33, 35, 37, 41, 43, 45, 103, 149, 163, 207, 225, 255, 269, 297, 341, 355, 395, 413, 439, 465, 493 cerebellar tonsils (cerebT), 21, 35, 43, 103, 151, 163, 207, 227, 265, 269, 297, 345, 355, 397, 413, 439, 465, 493

cerebellar vermis (cerebV), 21, 35, 43, 111, 151, 165, 211, 229, 267, 269, 299, 343, 355, 399, 415, 443, 465, 497 Cingulate gyrus (CingG), 21, 35, 87, 109, 133, 177, 195, 231, 265, 269, 303, 327, 367, 385, 415, 477, 495 Cingulate sulcus (CingS), 8, 20, 34, a42, 50-75, 87, 108, 132, 176, 194, 228, 264, 268, 302, 324, 366, 384, 414, 444, 476, 492, 522, 523 ascending ramus of cingulated sulcus (arCingS), 8, 20, 22, 34, 36, 42, 44, 50-75, 120, 148, 182, 212, 244, 264, 314, 340, 372, 400, 428, 456, 482, 508, 522, 523 Circular sulcus (circS,*), 108, 138, 174, 200, 230, 302, 334, 362, 388, 416, 444, 472, 494 Claustrum (3), 111, 139, 177, 199, 233, 305, 333, 365, 389, 417, 445, 497 Collateral sulcus (ColS), 20, 22, 34, 36, 42, 44, 50-75, 104, 140, 166, 200, 226, 258, 270, 298, 336, 358, 390, 412, 438, 468, 470, 522, 523, 526, 527 Colliculi inferior colliculi (ic), 111, 149, 173, 209, 233, 267, 269, 305, 343, 397, 419, 447, 473, 499 superior colliculi (sc), 111, 147, 173, 209, 235, 267, 269, 305, 341, 397, 421, 447, 473,501 Corpus callosum (CC), 21, 35, 43, 115, 139, 177, 201, 235, 267, 269, 307, 333, 369, 391, 421, 449, 479, 499

[537]


Corpus callosum (continued) beak of callosum (bcc), 21, 35, 43, 111, 137, 179, 199, 233, 265, 269, 305, 331, 367, 389, 447, 477, 497 splenium of callosum (sec), 21, 35, 43, 113, 147, 175, 209, 237, 265, 269, 307, 341, 365, 399, 423, 451, 475, 503, 526 Cuneus (Gun), 21, 35, 43, 113, 155, 167, 215, 237, 263, 269, 309, 345, 361, 403, 425, 451, 471, 505 Fornix (for), 21, 35, 43, 141, 177, 203, 235, 267, 269, 307, 335, 367, 393, 419, 447, 499 Frontal lobe (FL), 9, 87 Frontal pole (FP), 19, 21, 23, 33, 35, 37, 41, 43, 45, 107, 129, 179, 191, 227, 257, 269, 301, 323, 367, 381, 413, 443, 477, 491 Frontomarginal sulcus (FmS), 22, 36, 108, 128, 178, 190, 228, 258, 270, 302, 322, 370, 380, 412 Fusiform gyrus (FusiG), 21, 23, 35, 37, 43, 45, 111, 151, 169, 211, 235, 259, 273, 305, 345, 359, 401, 421, 447, 469, 499 Gyrus rectus (Grec), 21, 23, 35, 37, 43, 45, 107, 133, 175, 193, 227, 267, 269, 299, 325, 363, 383, 411, 441, 473, 491 Heschl's gyrus (HG), 27, 38, 46, 113, 143, 177, 205, 235, 255, 277, 305, 337, 367, 395, 419, 447, 475, 497 H shaped sulci (HsS), 20, 22, 34, 36, 42, 44, 130, 174, 192, 228, 258, 270, 300, 324, 364, 380, 412, 442, 472, 492 Hippocampal fissure (HipF), 108 Hippocampus (hip), 109, 143, 173, 203, 231, 259, 273, 301, 337, 361, 393, 415, 443, 471, 495, 526, 527 Hypothalamus (ht), 111, 143, 175, 203, 233, 265, 269, 335, 393, 417, 447, 475, 497 Inferior frontal gyrus (IFG), 19, 23, 33, 37, 41,45 pars opercularis (IFG,po), 19, 33, 41, 113, 139, 177, 199, 233, 253, 281, 305, 329, 367, 389, 417, 447, 477, 497 pars orbitalis (IFG.porb), 19, 33, 41, 109, 129, 177, 193, 229, 255, 281, 303, 327, 365, 383, 413, 445, 477, 495 pars triangularis (IFG,pt), 19, 33, 41, 111, 133, 177, 195, 231, 255, 279, 303, 325, 367, 383, 415, 445, 477, 495 Inferior frontal sulcus (IPS), 18, 22, 32, 36, 40, 44, 50-75, 108, 128, 180, 190, 228, 254, 276, 300, 326, 366, 382 ,414, 446, 494, 527, 530, 531 Inferior parietal lobule (IPL), 19, 33, 37, 41, 45 angular gyrus (AG), 19, 23, 33, 37, 41, 45, 115, 149, 171, 211, 237, 253, 275, 311, 343, 365, 403, 427, 451, 475, 505

[538]

supra-marginal gyrus (SMG), 19, 23, 33, 37, 41, 45, 115, 143, 177, 209, 239, 251, 279, 309, 337, 369, 397, 423, 451, 477, 503 Inferior temporal gyrus (ITG), 19, 21, 23, 33, 35, 37, 41, 43, 45, 107, 141, 169, 199, 227, 253, 279, 297, 335, 359, 389, 411,439,469,491 Inferior temporal sulcus (ITS), 18, 22, 32, 36, 40, 44, 50-75, 104, 140, 168, 198, 226, 252, 280, 296, 332, 360, 386, 410, 438, 468, 490, 526, 527 Insula (Ins), 9, 87 anterior gyri (1), 29, 109, 139, 177, 199, 231, 259, 277, 303, 331, 365, 389, 417, 445, 475, 497 anterior sulci (ants), 28 posterior gyri (2), 29, 109, 141, 175, 203, 231, 257, 277, 303, 335, 365, 391, 417, 445, 475, 497 posterior sulci (posts), 28 Internal capsule anterior (aic), 111, 141, 177, 203, 233, 265, 271, 305, 335, 367, 391, 419, 447, 477, 497 posterior (pic), 113, 141, 177, 205, 235, 265, 271, 305, 337, 367, 395, 419, 447, 477, 497 Intra-parietal sulcus (IPS), 18, 22, 32, 36, 40, 44, 50-75, 116, 146, 172, 214, 256, 272, 310, 340, 364, 402, 424, 452, 476, 506, 518 Lateral occipital gyri (LOG), 19, 23, 33, 37, 41, 45, 109, 153, 165, 213, 235, 253, 273, 305, 347, 359, 403, 421, 447, 469, 501 Lateral occipital sulcus (LOS), 18, 22, 32, 36, 40, 44, 114, 150, 170, 212, 236, 252, 278, 308, 346 ,404, 426, 446, 472, 502, 526 Lateral temporo-occipital sulcus (LTOS), 20, 22, 34, 36, 42, 44, 104, 140, 168, 196, 224, 258, 274, 296, 332, 358, 388, 410, 440, 468, 492, 526, 527 Lingual gyrus (LingG), 21, 23, 35, 37, 43, 45, 111, 149, 167, 211, 235, 263, 269, 305, 343, 361, 399, 419, 447, 469 ,499 Lingual sulcus (LingS), 20, 22, 34, 36, 42, 110, 152, 166, 212, 234, 264, 268, 306, 344, 362, 400, 420, 448, 468, 500 Mamillary body (mb), 21, 35, 109, 445, 473 Medulla (med), 19, 21, 23, 33, 35, 37, 41, 43, 45, 103, 149, 163, 205, 225, 2a67, 269, 297, 341, 355, 395, 411, 439, 465, 491 Mesencephalon (mes), 21, 35, 43, 111, 145, 173, 205, 233, 265, 269, 303, 339, 363, 395, 417, 473 Middle frontal gyrus (MFC), 19, 23, 33, 37, 41, 45, 109, 129, 181, 193, 229, 255, 275, 305, 325, 383, 415, 445, 479, 495

Middle frontal sulcus (MFS), 40, 44, 110, 446, 480, 494 Middle temporal gyrus (MTG), 19, 23, 33, 37, 41, 45, 107, 141, 171, 199, 227, 251, 281, 299, 333, 361, 365, 389, 413, 441, 471, 491 Midfrontal sulcus (mFS), 18, 22, 32, 36, 40, 114, 128, 184, 194, 234, 262, 270, 312, 324, 386, 424, 502 Occipital lobe (OL), 9, 87 Occipital pole (OP), 23, 37, 45 Occipitoparietal sulcus (OPS), 8, 20, 22, 34, 42, 50-75, 114, 152, 174, 214, 238, 264, 268, 308, 344, 364, 402, 424, 450, 474, 504, 519, 522, 523 Olfactory sulcus (OlfS), 50-75, 106, 134 Orbital frontal gyri anterior orbital gyrus (aOrbG), 21, 23, 35, 37, 43, 45, 109, 133, 177, 193, 227, 259, 273, 301, 327, 367, 383, 413, 443, 477, 493 lateral orbital gyrus (lOrbG), 21, 23, 35, 37, 43, 45, 109, 133, 177, 193, 229, 255, 277, 301, 325, 365, 383, 413, 443, 477, 493 middle orbital gyrus (mOrbG), 19, 23, 35, 37, 43, 45, 107, 133, 175, 193, 227, 263, 269, 299, 325, 365, 383, 413, 441, 473, 491 posterior orbital gyrus (pOrbG), 21, 23, 35, 37, 43, 45, 109, 135, 175, 195, 229, 259, 273, 301, 331, 363, 385, 413, 443, 473, 493 Orbital frontal sulci lateral orbital sulcus (LOrbS), 18, 22, 32, 36, 40, 44, 110, 130, 176, 192, 228, 254, 278, 300, 322, 366, 382, 412, 444, 478, 494 mid orbital sulcus (mOrbS), 20, 22, 34, 36, 42, 44, 106, 130, 174, 190, 226, 266, 268, 298, 324, 362, 380, 412, 440, 472, 490 suborbital sulcus (sOrbS), 20, 34, 42, 108, 128, 176, 190, 228, 322, 366, 380, 412, 442, 476, 494 Pallidum (pa), 111, 141, 177 ,203, 233, 263, 273, 305, 335, 365, 391, 419, 447, 477, 497 Paracentral gyrus (paraCG), 21, 35, 43, 121, 143, 183, 209, 243, 267, 269, 315, 333, 373, 395, 429, 457, 483, 507 Paracentral sulcus (paraCS), 20, 34, 42, 120, 140, 184, 208, 242, 266, 268, 314, 334, 374, 426, 456, 484, 506 Parahippocampal gyrus (paHG), 21, 23, 35, 37, 43, 45, 107, 143, 171, 201, 229, 259, 273, 299, 335, 359, 363, 391, 415, 441, 471, 493 Parietal lobe (PL), 9, 87 Planum temporale (PT), 27, 38, 46

Pons (pons), 21, 23, 33, 35, 37, 41, 43, 45, 105, 145, 167, 203, 227, 265, 269, 297, 339, 357, 393, 413, 441, 467, 493 Postcentral gyrus (postCG), 19, 23, 33, 37, 41, 45, 115, 141, 177, 203, 235, 251, 271, 307, 335, 367, 393, 421, 449, 477, 499 Postcentral sulcus (postCS), 8, 18, 22, 32, 36, 40, 44, 50-75, 114, 142, 178, 204, 240, 250, 272, 308, 336, 368, 394, 422, 450, 476, 502, 518, 519, 530, 531 Posterior commisure (pc), 21, 35, 43, 501 Precentral gyrus (preCG, preCg), 19, 23, 33, 37, 41, 45, 111, 139, 179, 201, 233, 251, 271, 305, 333, 367, 391, 419, 449, 477, 499 Precentral sulcus (preCS), 8, 18, 22, 32, 36, 40, 44, 50-75, 112, 136, 178, 200, 232, 252, 270, 304, 332, 368, 390, 418, 448, 476, 498, 518, 519, 527, 530, 531 Precuneus (preCun), 21, 35, 43, 115, 149, 173, 215, 239, 267, 269, 273, 311, 343, 365, 405, 425, 453, 477, 507 Putamen (pu), 111, 137, 177, 199, 231, 261, 271, 303, 333, 365, 389, 417, 445, 475, 497

Index

Quadrigeminal plate (qpl), 21, 35, 43 Retrosplenial area (rSp), 21, 35, 43, 113, 149, 175, 211, 237, 263, 269, 307, 343, 365, 399, 423, 449, 475, 501 Pxhinal sulcus (RhS, rhS), 20, 34, 42, 106, 172, 300, 360, 412, 440, 470, 492 Spinal cord (sc), 19, 21, 23, 33, 35, 37, 41, 43, 45, 151, 205, 225, 269, 345, 355, 395, 491 Subparietal sulcus (sPS), 20, 34, 42, 116, 148, 174, 214, 238, 264, 268, 310, 340, 366, 400, 454, 476, 504, 519, 522, 523 Superior frontal gyrus (SFG), 19, 21, 23, 33, 35, 37, 41, 43, 45, 111, 129, 183, 193, 231, 259, 269, 305, 323, 373, 381, 415, 445, 481, 495 Superior frontal sulcus (SFS), 18, 22, 32, 36, 40, 44, 50-75, 112, 128, 182, 192, 230, 256, 274, 302, 324, 370, 380, 414, 444, 478, 492, 518, 527, 530, 531 Superior parietal lobule (SPL), 19, 23, 33, 37, 41, 45, 119, 147, 173, 215, 241, 259, 271, 313, 343, 365, 403, 429, 453, 477, 509 Superior temporal gyrus (STG), 19, 23, 33, 37, 41, 45, 109, 139, 175, 199, 229, 251, 279, 301, 333, 363, 389, 415, 443, 475, 493 Superior temporal sulcus (STS), 18, 22, 32, 36, 40, 44, 50-75, 106, 138, 172, 200, 228, 250, 278, 298, 332, 362, 386, 412, 438, 470, 490, 526, 527, 530, 531

[539]


[540]

Superior temporal sulcus (continued) inferior ramus (STSir), 114, 150, 176, 214, 238, 250, 282, 310, 364, 404, 426, 474, 502 superior ramus (STSsr), 8, 116, 150, 176, 214, 238, 250, 280, 310, 346, 366, 402, 426, 452, 474, 502 Sylvian fissure (SF), 8, 18, 22, 32, 36, 40, 44, 50-75, 87, 108, 138, 176, 198, 230, 250, 278, 302, 330, 364, 386, 416, 444, 476, 494, 518, 519, 526, 527, 530, 531 ascending branch of sylvian fissure (abSF), 8, 18, 22, 32, 40, 50-75, 110, 136, 176, 198, 232, 252, 278, 304, 330, 366, 388, 416, 446, 476, 496, 527, 530, 531 horizontal branch of sylvian fissure (hbSF), 8, 18, 32, 40, 50-75, 110, 134, 176, 196, 254, 280, 302, 326, 366, 414, 444, 476, 494, 530, 531

Temporal pole (TP), 19, 21, 23, 33, 35, 37, 41, 43, 45, 103, 137, 169, 197, 225, 257, 273, 297, 331, 361, 385, 411, 439, 469, 491 Temporo-occipital gyrus (TOG), 21, 23, 35, 37, 43, 45, 105, 141, 167, 201, 227, 257, 277, 297, 335, 359, 389, 411, 439, 469, 491 Thalamus (th), 21, 35, 43, 113, 143, 175, 203, 235, 263, 269, 305, 337, 365, 393, 419, 447, 475, 499 Transverse occipital sulcus (trOS, trsOS), 18, 22, 32, 36, 40, 44, 114, 156, 170, 218, 238, 256, 272, 308, 350, 362, 420, 452, 474, 504, 526, 527 Transverse temporal sulcus (trTS), 27, 38, 46, 112, 142, 176, 208, 234, 254, 278, 306, 336, 364, 392, 418, 446, 474, 502, 527

Temporal lobe (TL), 9, 87

Uncus (uncus), 21, 35, 43

Human Brain Anatomy in Computerized Images - Hanna Damasio

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