Brain Structure and Its Origins
Brain Structure and Its Origins
in Development and in Evolution of Behavior and the Mind
Gerald E. Schneider
The MIT Press
Cambridge, Massachusetts
London, England
© 2014 Massachusetts Institute of Technology
All rights reserved. No part of this book may be reproduced in any form by any electronic or mechanical means
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Library of Congress Cataloging-in-Publication Data
Schneider, Gerald E.
Brain structure and its origins : in development and in evolution of behavior and the mind / Gerald E.
Schneider.
pages cm
Includes bibliographical references and index.
ISBN 978-0-262-02673-4 (hardcover : alk. paper) 1. Brain. 2. Brain—Evolution. I. Title.
QP376.S348 2014
612.8′2—cd23
2013023059
10
9
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1
This book is dedicated to the memory of my mother and father and my youngest sister,
Linda Jean. Their enthusiastic support is always with me.
Contents
Detailed contents
Preface
xxiii
xi
PART I: INTRODUCTORY ORIENTATION
1
2
1
Getting Ready for a Brain Structure Primer 3
Methods for Mapping Pathways and Interconnections That Enable the Integrative Activity
of the CNS 29
PART II: THE CENTRAL NERVOUS SYSTEM, FROM INITIAL STEPS TO ADVANCED
CHORDATES 53
3
4
Evolution of Multicellular Organisms with Neuron-Based Coordination
Expansions of the Neuronal Apparatus of Success 67
55
PART III: INTRODUCTION TO CONNECTION PATTERNS AND SPECIALIZATIONS IN
THE EVOLVING CNS 87
5
6
7
The Ancestors of Mammals: Sketch of a Pre-mammalian Brain 89
Some Specializations Involving Head Receptors and Brain Expansions 107
The Components of the Forebrain Including the Specialty of the Mammals: The
Neocortex 117
PART IV: DEVELOPMENT AND DIFFERENTIATION: SPINAL LEVEL
8
9
137
The Neural Tube Forms in the Embryo, and CNS Development Begins 139
The Lower Levels of Background Support: Spinal Cord and the Innervation of the
Viscera 153
Intermission: The Ventricular System, the Meninges, and the Glial Cells 175
viii
Contents
PART V: DIFFERENTIATION OF THE BRAIN VESICLES
10
11
12
13
Hindbrain Organization, Specializations, and Distortions 181
Why a Midbrain? Notes on Evolution, Structure, and Functions
Picturing the Forebrain with a Focus on Mammals 217
Growth of the Great Networks of Nervous Systems 235
PART VI: A BRIEF STUDY OF MOTOR SYSTEMS
14
15
16
263
309
Widespread Changes in Brain State
PART VIII: SENSORY SYSTEMS
18
19
20
21
22
23
205
Overview of Motor System Structure 265
Descending Pathways and Evolution 283
The Temporal Patterns of Movements 299
PART VII: BRAIN STATES
17
179
311
323
Taste 325
Olfaction 333
Visual Systems: Origins and Functions 355
Visual Systems: The Retinal Projections 371
The Visual Endbrain Structures 393
Auditory Systems 417
PART IX: THE FOREBRAIN AND ITS ADAPTIVE PRIZES: A SNAPSHOT
24
Forebrain Origins: From Primitive Appendage to Modern Dominance
PART X: THE HYPOTHALAMUS AND LIMBIC SYSTEM
25
26
27
28
29
447
449
465
Regulating the Internal Milieu and the Basic Instincts 467
Core Pathways of the Limbic System, with Memory for Meaningful Places
Hormones and the Shaping of Brain Structures 501
The Medial Pallium Becomes the Hippocampus 513
The Limbic Striatum and Its Outpost in the Temporal Lobe 537
483
ix
Contents
PART XI: CORPUS STRIATUM
30
31
559
The Major Subpallial Structure of the Endbrain 561
Lost Dopamine Axons: Consequences and Remedies 583
Intermission: Neurogenesis in Mature Brains 589
PART XII: THE CROWN OF THE MAMMALIAN CNS: THE NEOCORTEX
32
33
34
593
Structural Origins of Object Cognition, Place Cognition, Dexterity, and Planning
Basic Neocortical Organization: Cells, Modules, and Connections 617
Structural Change in Development and in Maturity 645
Figure Credits
Index 679
669
595
Detailed Contents
Preface
xxiii
PART I: INTRODUCTORY ORIENTATION
1
1
Getting Ready for a Brain Structure Primer
3
The Nature of This Book 3
Brain Space: Specifying Directions and Major Regions 5
CNS Tissue
9
Primitive Cellular Mechanisms 12
Irritability and Conduction 13
The Specialized Membrane of the Axon
15
Specializations for Irritability 19
Movement
19
Secretion
20
Synaptic Morphology and Types
21
Related Cellular Dynamics 23
Parallel Channels of Information Flow and Integrative Activity
Endogenous Activity
25
Readings 27
2
25
Methods for Mapping Pathways and Interconnections That Enable the Integrative Activity
of the CNS 29
Histology and Brain Architecture
29
What Is Connected to What? 35
Tracing a Pathway from Sensory Input to the Response (S to R)
Pathways Seen as Bundles and Ribbons of Fibers 41
Experimental Studies Needed to Trace Connections in the Brain
Experimental Neuroanatomy: Tract-Tracing Methods
42
Readings 51
38
41
xii
Detailed Contents
PART II: THE CENTRAL NERVOUS SYSTEM, FROM INITIAL STEPS TO ADVANCED
CHORDATES 53
3
Evolution of Multicellular Organisms with Neuron-Based Coordination
Basic Survival Skills 55
The First Neurons and Nerve Networks
56
The Nervous System in Basic Concept
58
Some Terminology for Brain Talk 59
Introducing the Simplest Chordates
60
Natural Selection and the Logic of Evolution 63
The Behavioral Demands That Changed the Neural Tube
Readings 65
4
Expansions of the Neuronal Apparatus of Success
55
63
67
Why We Can Talk about Broad Aspects of Brain Evolution with Some Confidence 67
Three Enlargements Formed the Primitive Brain
67
Expansions of the Hindbrain
69
Early Forebrain Expansion Served Olfactory Functions
72
Midbrain Expansions, Distance Receptors, and Decussations
75
A Second Expansion of the Forebrain with Invasion of Non-olfactory Inputs
77
Concurrent Evolutionary Changes: Motor Control and Plasticity 79
Concurrent Evolutionary Changes: Motivational States 80
A Third Expansion of the Forebrain: Anticipating Events and Planning Actions
81
Brain Sizes Relative to Body Weight Compared for Present-Day Animals 81
Where We Stand in the Path to Our Goal
83
Readings 84
PART III: INTRODUCTION TO CONNECTION PATTERNS AND SPECIALIZATIONS IN
THE EVOLVING CNS 87
5
The Ancestors of Mammals: Sketch of a Pre-mammalian Brain
The “Old Chassis” for the Building of Further Additions 90
Subdividing the CNS 94
The Basic Setup: Major Types of Neurons 96
Sensory Channels of Conduction: Local Reflex, and Not so Local
Old Ribbons to the Brain 101
Ribbons to the Little Brain: The Cerebellum 103
Readings 106
6
89
97
Some Specializations Involving Head Receptors and Brain Expansions
Electroreception and the Cerebellum
107
Infrared Sensors in Pit Vipers 109
Echolocation and the Auditory System 110
The Visual Systems of Primates 111
Whisker Fields and Barrel Fields 111
Other Behavioral Specializations with Corresponding Enlargements of Brain Parts
Readings 116
107
112
xiii
Detailed Contents
7
The Components of the Forebrain Including the Specialty of the Mammals: The
Neocortex 117
Forebrain Removal Experiments 117
Cat Behavior after Forebrain Removal 117
Rat Behavior Is Less Drastically Affected by Forebrain Removal 118
Pigeons after Forebrain Removal, Sparing the Optic Tracts 119
Forebrain Function: A Conclusion
120
The Problem of Species Differences in Brain Lesion Effects
120
The Phenomena of Diaschisis: An Answer to the Problem
120
What Can We Conclude about Interpreting Effects of Brain Lesions? 123
Role of the Corpus Striatum 123
The Rostral End of the Brainstem Located between the Hemispheres (’Tweenbrain)
Limbic System of the Forebrain 125
Olfactory System Origins of Major Functions of the Limbic Endbrain 126
Overview of the Roles of Corpus Striatum and Limbic Forebrain 128
Neocortex, the Grand Innovation of the Mammals: Appearance of New Pathways
But What Does It Do? Why Did Neocortex Evolve?
134
Taking Stock
134
Readings 135
PART IV: DEVELOPMENT AND DIFFERENTIATION: SPINAL LEVEL
8
9
128
137
The Neural Tube Forms in the Embryo, and CNS Development Begins
Before There Is Any CNS 139
The Onset of a Nervous System
140
Molecules from the Notochord Induce the Formation of the Nervous System
The Neural Crest Gives Rise to the PNS 142
Cell Proliferation in the Early Neural Tube 143
Diversity in Neuronal Migration
145
Differentiation of the Neurons Begins 149
Notes
150
Readings 150
124
139
141
The Lower Levels of Background Support: Spinal Cord and the Innervation of the
Viscera 153
Major Features of Cord Structure 153
Questions from Comparing Different Species 156
The Local Reflex Channel and the Older Lemniscal Channels
158
The Mammalian Highway for Ascending Somatosensory Information 161
Cerebellar Channel
162
The Pathways of Regulation within the Spinal Cord Itself
163
The Pathways of Influence and Control from the Brain
164
A Reminder
165
Maintaining Stability of the Internal Environment: The Autonomic Nervous System
Three Major Divisions of the Motor System 166
A Sketch of the Autonomic Nervous System 167
Chemical Mediation at Autonomic Nervous System Synapses 171
166
xiv
Detailed Contents
The Enteric Nervous System
171
Levels of Control of the Internal Environment
Readings 173
173
Intermission: The Ventricular System, the Meninges, and the Glial Cells
Readings
PART V: DIFFERENTIATION OF THE BRAIN VESICLES
10
179
Hindbrain Organization, Specializations, and Distortions
A Glamorized Spinal Cord
181
Vital Functions of the Hindbrain 183
Routine Maintenance Services 184
Hindbrain Participation in Mammalian Higher Functions
The Isodendritic Core of the Brainstem 185
Segmentation of the Hindbrain
186
Columns and Cranial Nerves
188
The Adult Hindbrain: Cell Groups and Axons of Passage
Somatosensory Inputs from the Face 193
The Evolution of Crossed Projections 194
Hindbrain Sensory Channels in Mammals 197
Hindbrain Specializations and Mosaic Evolution 199
Readings 204
11
181
184
192
Why a Midbrain? Notes on Evolution, Structure, and Functions
Primitive Vision
206
Primitive Olfaction
206
A Structural Consequence of the Priority of Escape Behavior for Survival
The Midbrain Correlation Centers
208
Outputs of Midbrain for Motor Control
210
Mosaic Evolution of Midbrain
212
Long Axons Passing through the Midbrain 212
Readings 216
12
175
178
Picturing the Forebrain with a Focus on Mammals
217
Pictures of Ancestral and Modern Endbrain
218
Words for Forebrain Parts
220
Major Structural and Functional Subdivisions of the ’Tweenbrain
220
Major Parts of the Telencephalon of Mammals 222
Origins and Course of Two Major Pathways of the Forebrain 222
The Neocortex Is Involved in Both Major Systems 224
Interim Review of Neuroanatomy
226
Segmentation of the Forebrain
227
Notes on Neocortical Origins
227
Readings 232
205
207
xv
Detailed Contents
13
Growth of the Great Networks of Nervous Systems
235
The Axonal Growth Cone
235
Signals That Shape the Development of Neuronal Circuits 239
Four Types of Chemical Guidance 244
Two Modes of Axon Growth 247
Formation of Maps in the Brain 247
Plasticity in Brain Maps
249
More Plasticity in the CNS: Collateral Sprouting 252
Modulation of Competitive Axonal Growth Vigor
255
Rules of Sprouting Apply to Development, with Implications for Evolutionary Change
Plasticity in the Small Interneurons of the Adult Brain
256
Structural Regression during Development and Its Purposes 257
Axon Loss in the Damaged CNS: Is Regeneration Possible?
258
Readings 259
PART VI: A BRIEF STUDY OF MOTOR SYSTEMS
14
Overview of Motor System Structure
256
263
265
A Functional Starting Point for the Study: Three Major Types of Movement Critical for Survival 265
Midbrain Control of the Three Types of General-Purpose Movement
266
The Midbrain Was the Connecting Link between the Primitive Forebrain and Motor Systems 267
Head Receptors and Locomotor Approach and Avoidance 268
Initiation of Foraging by Activity Intrinsic to the Brain 268
The Motor System Hierarchy
269
Locomotor Pattern Generation and Its Adjustments by Vestibular and Cerebellar Systems
269
Orienting of Head and Body 272
Grasping: The Third Major Type of Movement Controlled by the Midbrain
275
Comparative Anatomy of the Red Nucleus and Its Projection to the Spinal Cord 275
A Structural Approach to Understanding Motor Control: Begin with the Motor Neurons 277
The Spatial Arrangements of Somatic Motor Neurons in the Spinal Cord
278
Readings 281
15
Descending Pathways and Evolution
283
Axons Descending from Brain to Spinal Cord: Functional Groupings 283
Functions of the Descending Pathways: The Corticospinal Tract 286
Functions of the Descending Pathways: The Medial Hindbrain Tracks 287
Functions of the Descending Pathways: The Lateral Brainstem Tracks
287
A Conclusion with Application to Humans 289
The Brain Disconnected from the Motor Pattern Generators 289
Importance of the Corticospinal Tract for Innate and Learned Movements That Require Special
Dexterity
290
The Nature of the Spinal Motor Pattern Generators 291
Motor Cortex in Phylogeny
291
Corticospinal Projections in Phylogeny
293
The Highest Levels of Motor Control
296
Readings 296
xvi
Detailed Contents
16
The Temporal Patterns of Movements
299
Three Types of Mechanism
299
Explaining Movement Dynamics in Terms of S-R Circuits 300
Central Programs Rather than Reflex Chaining
302
Many Fixed Action Patterns Are Centrally Generated 302
Reverberating Circuits within the Brain and Spinal Cord 303
Endogenous Activity of Single CNS Neurons 304
The Endogenous Clock 304
How It All Works at the Circuit Level 305
The Circuits Are Not Always Fixed
305
How Adequate Are These Concepts? 306
Readings 306
PART VII: BRAIN STATES
17
309
Widespread Changes in Brain State
311
Brain States Influenced by Widely Projecting Axon Systems 311
Cholinergic Systems
312
The Monoamine-Containing Systems 313
Serotonin, Another Monoamine Neurotransmitter Influencing Behavioral State
Diencephalic Origins of Other Widely Projecting Axon Systems 316
How Many Different Brain States? 318
Readings 320
PART VIII: SENSORY SYSTEMS
18
Taste
323
325
Pre-chordate Taste and Other Chemoreceptor Systems
Olfaction or Taste? 326
Visceral and Taste Inputs to the Hindbrain 326
Innervation of the Tongue
327
Distribution of Mammalian Taste Receptors 327
From Tongue to Telencephalon
328
Purposes of Taste: Routes to Motor Control 330
Readings 331
19
Olfaction
325
333
Sections through the Forebrain of Vertebrates
333
Olfactory Bulb Projections in Primitive Vertebrates
336
Variations in Relative Size of Olfactory Systems 338
Olfactory Bulb Projections in Mammals 339
Human and Small Mammalian Brains 341
Neuronal Organization as Depicted by Ramón y Cajal 341
The Axons of the Lateral Olfactory Tract 344
Overview
346
315
xvii
Detailed Contents
Spatial Organization of the Primary Sensory Neurons 347
Beyond the Mitral Cells
349
Ongoing Plasticity in the Olfactory Bulb by Cell Turnover
350
Olfaction and Behavior 351
Readings 352
20
Visual Systems: Origins and Functions
355
Origins of Vision, 1: Light Detection 356
Origins of Vision, 2: Image Formation
358
Predator Avoidance and Escape: A Hypothesis Concerning Evolution and the Origins of Crossed
Projections
359
Orienting Toward or Around Visually Detected Objects and Other Responses 361
The Midbrain Tectum and Orienting Toward Novel Objects, Food, or Potential Mates or
Rivals 363
Identifying Animals, Objects and Textures 364
The Invasion of the Endbrain by Visual Pathways: Likely Evolutionary Steps in Pre-mammalian and
Mammalian Ancestors
365
More about the Third Role of Visual Images 366
Expansions and Specializations in the Visual System 367
Readings 369
21
Visual Systems: The Retinal Projections
371
Two Views of the Optic Tract and Its Terminations
371
Distortions in Large Primates
374
How the Optic Tract Looks in the Brain of an Adult Animal 375
Looking at the Exposed Brain from Above 380
The Embryonic Optic Tract
381
Midbrain Tectum: Species Differences
384
Lamination of the Midbrain Tectum 385
Topographic Organization of the Retinal Projection to the Midbrain Surface
Notes
391
Readings 392
22
The Visual Endbrain Structures
385
393
Multiple Routes from Retina to the Endbrain 393
The Visual System’s Two Major Routes to the Endbrain in Phylogeny
395
The Route through the Lateral Geniculate Body 397
Early Myelination of the Optic Radiations
399
The Brain and Neocortex in Human Development and in Phylogeny 399
Evolutionary Multiplications of Cortical Representations of the Retina 404
Comparing Species: Evidence for Older and Newer Visual Cortical Areas 407
And Where Do We Go from Here?
407
Transcortical Pathways from Visual Cortex 409
Three Visual Pathways and Their Functions
411
The Third Major Transcortical Pathway 412
Comments on Transcortical Interconnections
414
Readings 415
xviii
Detailed Contents
23
Auditory Systems
417
Embryonic Placodes Give Rise to Auditory and Vestibular Nerves 417
The Auditory Pathway (in Brief) 418
Some Special Functions of the Auditory System: Antipredator Behaviors
418
Aversiveness of Noise and the Role of the Limbic System 419
Learned Fear: Importance of the Forebrain
420
Predation Had Other Requirements: Identifying and Localizing Prey Animals
421
Transformations of Sound Vibrations in Middle Ear and Cochlea
423
Evolution of Jaw Bones of Ancestral Reptiles into the Ossicles of the Middle Ear in Mammals
424
Mammalian Ear Structures and Dynamics 425
Initial Coding of Information
426
The Flow of Auditory Information in the CNS 428
Terminations of the Auditory Nerve 428
Thalamic Projections Carry Auditory Information to the Limbic System and to Neocortex 430
Review: Multiple Routes Carrying Auditory Information to the Forebrain 430
Distinct Pathways for Two Major Functions: Orienting and Identification 431
Location Specificity Arises in Cells of the Hindbrain’s Trapezoid Body 431
How Direction Can Be Derived from Precise Time-of-Arrival at the Two Ears 432
A Second Hindbrain Mechanism for Sound Localization 434
How Did This Spatial Localization Apparatus of the Hindbrain Evolve? 434
Judging a Sound’s Direction in the Vertical Axis 434
Location Information Reaches the Midbrain’s Superior Colliculus 434
Location Information Also Reaches the Endbrain
435
The Second Function of Ascending Auditory Pathways: Pattern Identification
435
Temporal Pattern Selectivity: Examples
438
Functionally Distinct Auditory Pathways in the Neocortex 440
Auditory System Specializations 442
Readings 445
PART IX: THE FOREBRAIN AND ITS ADAPTIVE PRIZES: A SNAPSHOT
24
Forebrain Origins: From Primitive Appendage to Modern Dominance
Life without a Forebrain
449
In Search of Ideas about Origins: Primitive Forebrains 450
Brain Expansions in the Vertebrates 452
More about the Early Forebrain 456
The Scene Is Set for the Early Expansion of the Striatum
456
Another Kind of Plasticity in the Primitive Endbrain 457
Parallel Evolution of Pallium and Subpallium 459
Visualizing the Early Striatum and Pallium
460
Next Steps into the Forebrain 463
Readings 463
447
449
xix
Detailed Contents
PART X: THE HYPOTHALAMUS AND LIMBIC SYSTEM
25
Regulating the Internal Milieu and the Basic Instincts
465
467
Nature of the Hypothalamus and Affiliated Structures: The Limbic System 467
Approaching the Limbic System from Below: Two Kinds of Arousal from the Midbrain 468
Autonomic and Endocrine Functions of the Hypothalamus 470
Homeostatic Regulation of the Internal Milieu
472
Regulation of Cyclic and Episodic Behaviors 473
The Center of Motivational State Control
474
Distinguishing between Appetitive and Consummatory Behaviors Involved in a Drive 474
Computational Neuroethology
475
Hunger, Feeding, and Brain Circuits 476
Electrically Elicited Drive States
476
Connections with Other Systems
478
Drive and Reward Involve Distinct Axon Populations in the Medial Forebrain Bundle 479
Readings 479
26
Core Pathways of the Limbic System, with Memory for Meaningful Places
Cell Groups in the Hypothalamus 483
Feedback from Visceral Afferents and from Blood Chemistry 484
Limbic System Interconnections within the Forebrain: The Circuit of Papez
Why the Revival of Interest in This Circuit? 490
Visualizing the Circuit of Papez 490
What Is the Functional Significance of the Return Pathway?
492
Place Memories in the Neuronal Pathways of Feeling and Emotion 493
Review of Structures in the Limbic System 493
A Variety of Ways the Hypothalamus Sends Its Influences to the Neocortex
Mental State and the Hypothalamus 497
Influence of the Hypothalamus on the Brainstem and Spinal Cord 497
Review
498
Functional Specificity in the Limbic Midbrain 498
Readings 499
27
Hormones and the Shaping of Brain Structures
486
494
501
Sex Differences in the Human CNS: Evidence from Pathologies
502
What Determines an Individual’s Sexual Orientation? 502
Hormone Peaks and Brain Differentiation 503
More Sex Differences in the CNS
504
Sexual Dimorphism Underlying Singing in the Canary and Other Songbirds
“A Brain for All Seasons”
507
How Many More Sex Differences in the Brain Will Be Found?
508
Back to the Anatomy of the Limbic System 510
Readings 511
506
483
xx
Detailed Contents
28
The Medial Pallium Becomes the Hippocampus
513
Evidence of an Internal Map: Place Cells 513
Head-Direction Cells and the Circuit of Papez 515
Thoughts about the Origins of the Medial Pallium 517
The Expansion of the Pallium, with a Focus on the Medial Pallium 518
Cells and Circuits of Ammon’s Horn (Cornu Ammonis)
520
Further Notes on Hippocampal Anatomy 520
Major Connections between the Mammalian Hippocampus and Neocortex
Local Circuits within the Hippocampus 527
Memory and the Hippocampus
527
Subcortical Projections to and from the Hippocampus 528
Anatomical Plasticity in the Hippocampus 529
Brain States and Memory Consolidation during Sleep 531
Readings 533
29
The Limbic Striatum and Its Outpost in the Temporal Lobe
523
537
A Brain System of Forebrain and Midbrain Underlying Motivation, Emotion, and Autonomic
Regulation 537
What Is the Amygdala?
539
The Stria Terminalis: A Major Output of the Amygdala
542
Sensory Pathways to the Amygdala 542
Amygdala Connections with Systems of Higher Cognitive Functions 545
Behavioral Change Caused by Artificial Activation of the Amygdala 545
Behavioral Change after Amygdala Lesions 547
How Sounds That Warn of Danger Come to Cause Fear and Avoidance 547
The More Rostrally Located Ventral Striatum, in the “Basal Forebrain”
548
Disordered Functions of the Limbic System
551
Other Behavioral Difficulties in People Are Tied to Amygdala Functions 554
Central Roles of Basal Forebrain and Amygdala for Learned Affects 556
Readings 557
PART XI: CORPUS STRIATUM
30
559
The Major Subpallial Structure of the Endbrain
561
Beginnings: A Link between Olfactory Inputs and Motor Control
561
Non-olfactory Inputs Invade the Striatum 562
Visualizing the Striatum and Other Major Structures in the Cerebral Hemisphere
Major Outputs of the Mammalian Endbrain: The Position of the Striatum
564
Simplified Pictures of Dorsal Striatal Connections
568
Diaschisis after Loss of Inhibitory Connections
571
The Striatal Satellites Add Complexity to the System 573
Neocortex Dominates the Inputs to Dorsal Striatum of Large Mammals 574
Topography in the Ventral Striatum 575
Complex Chemoarchitecture of the Striatum 578
Compartmental Organization within the Striatal System
578
Finding the Corpus Striatum in Large Mammalian Brains 580
Overview
580
Readings 582
564
xxi
Detailed Contents
31
Lost Dopamine Axons: Consequences and Remedies
583
Fetal Nigral Tissue Transplantation Initiated as a Therapy for Parkinson’s Disease
583
Initial Promise of Transplant Treatments 585
Deep Brain Stimulation or Selective Surgical Lesions in Advanced Parkinson’s Disease
585
Additional Alternative Treatments 586
Readings 588
Intermission: Neurogenesis in Mature Brains
Readings
589
590
PART XII: THE CROWN OF THE MAMMALIAN CNS: THE NEOCORTEX
32
593
Structural Origins of Object Cognition, Place Cognition, Dexterity, and Planning
The Primitive Olfactory Functions of Endbrain: Identification of Object and Place
595
The Advantages and Consequences of Non-olfactory Inputs to the Endbrain 597
In Mammals, Why Did Neocortex Evolve Rather than Wulst?
597
The Orderly Architecture of Neocortex Illustrated by the Human Brain 598
Basic Sensorimotor Functions of Neocortex 601
Functional Regions Based on the Early Evolution of Place Cognition and Object Cognition
Sensory Cortex That Led to the Evolution of Fine Motor Control
603
Anticipation as a Major Innovation of the Neocortex 603
Origins of Planning 604
Neocortex as Anticipator and Planner: Illustrative Evidence 604
Endbrain Evolution: Suggested Major Steps Reviewed and Extended 605
Expansions of Neocortical Areas
609
Evolutionary Changes in Thalamocortical Axon Trajectories 611
Readings 614
33
Basic Neocortical Organization: Cells, Modules, and Connections
595
601
617
Two Major Types of Neocortical Neuron
617
The Major Morphological Characteristics of the Neocortex 617
Modules of the Neocortex: Areas and Columns 619
Cortical Types and Variations
623
Connections of the Neocortical Modules 624
Convergence of Inputs, Great and Small
626
Expansions of the Neocortex Reviewed 627
Axons to and from Neocortex 627
Ascending Pathways to Neocortex Go Mainly through the Thalamus: The Basic Pattern 628
Illustrations of Thalamocortical Connections: Human Brain
629
Illustrations of Thalamocortical Connections: Brain of Small Rodent or Insectivore 633
Transcortical Association Fibers 634
Comparative Neocortical Anatomy from a Moscow Perspective 639
Studies of Development and Plasticity Lend Support to Classifications of Major Neocortical
Types
640
Review of Ideas on Thalamic Evolution
642
Readings 643
xxii
34
Detailed Contents
Structural Change in Development and in Maturity
645
Neuronal Proliferation 645
Neocortical Expansion in Development and in Evolution 646
When Cortical Cells Are Born and How They Migrate
650
How Do Distinct Cortical Areas Become Specified in Development?
652
The Role of Activity in the Development of Neocortical Connections 654
Apparent Shaping of Thalamocortical Projections by Abnormal Activity 656
How Does Activity Affect Axons and Their Connections? 656
Altered Neocortical Structure after Early Blindness
659
Alteration of Receptive Fields by Repetitive Stimulation in Adult Somatosensory Cortex 660
Review: Where Are the Engrams? 663
Is Everything Plastic? 664
Conclusions about the Neocortex
664
Posterior (Postcentral) Portions of the Hemisphere
664
Rostral (Frontal) Portions of the Hemisphere 665
Brain State Changes Can Alter the Processes of Both Posterior and Frontal Portions of the Neocortex
665
The Study of Brain Structure and Its Origins Lays the Groundwork for Understanding the Underpinnings of Behavior
and Mental Abilities 666
Readings
666
Figure Credits
Index
679
669
Preface
The first draft of this book was based on classes I have taught in the MIT Brain and
Cognitive Sciences Department for many years, including classes for undergraduates. The
book is also based on an introduction to neuroanatomy I teach to beginning graduate
students. Finding no available textbook that fitted what I wanted for these classes led me
to start writing the book. In the writing, I have assumed that readers have had some
exposure to biology or to anatomy and physiology. This book can be useful to advanced
undergraduates, to graduate students studying psychology, biology, zoology, or neuroscience, and to interested readers in other fields. More generally, the book is for any persons
who wants to gain greater familiarity with the nervous system and how it works. It will
be useful also for scientists, bioengineers, and medical personnel who have plunged into
work on details of a particular portion of the brain and want to fill out their picture of
how that part fits into the whole system.
The book is not primarily about evolution. It is about the structure and functional
significance of the central nervous system (CNS), especially the major structures and their
interconnections in the brains of vertebrates with a special focus on mammals. CNS
structure and its variations among vertebrates can be learned and understood more easily
if one knows something about why it is so. The “why” can be answered in terms of functions, in terms of evolution, or in terms of development. In this book, I consider each of
these three aspects of why the brain is put together as it is, because they make the structure more comprehensible as well as more interesting and memorable.
Brain evolution is presented in broad outline, based primarily on comparative neuroanatomical findings. The great importance of functional adaptations in evolution as
described by Charles Darwin is assumed. Darwinian theory as updated in modern times,
together with comparative neuroanatomical findings, are used to guide the formulation
of suggested explanations of some key steps in early chordate CNS evolution.
The major goal is to help the student of brain anatomy and function gain an outline
that she or he can use in further explorations of this field. It is a field that can seem formidably intimidating at first but fascinating and rewarding to the explorers who persist
in going through the territory and learning the rudiments of the language.