Hemispheric specialization is involved in every aspect of sensory, cognitive, and motor systems integration. Study of the corpus callosum, the bands of tissue uniting the brain's two hemispheres, is central to understanding neuroanatomy, neurophysiology, and behavior. It also brings the tools of hemispheric specialization to a fundamental problem of cognitive neuroscience: modularity and intermodular communication.This book summarizes current research on the human corpus callosum. It also provides a comprehensive introduction to cognitive neuroscience. Rather than viewing the field through the various systems of the mind/brain such as perception, action, emotion, memory, language, and problem solving, it takes a case studies approach. Focusing on the central problem of simple reaction time, it examines the most basic possible sequence of perception-decision-action. The task is to press a button with one hand as soon as a patch of light is detected in the peripheral visual field. When the patch appears in the visual field opposite the responding hand, there must be interhemispheric transfer prior to response. But transfer of what--a visual input code? A cognitive decision code? A motor response code? Combining animal models, normal human studies, and clinical evidence, the authors apply anatomical, physiological, and behavioral perspectives to this question. The emerging view is that the corpus callosum consists of many parallel interhemispheric channels for communication and control, and that every transfer channel is context-dependent and modulated by attention.
Author(s): Eran Zaidel, Marco Iacoboni
Series: Issues in Clinical and Cognitive Neuropsychology
Edition: 1
Publisher: The MIT Press
Year: 2002
Language: English
Pages: 580
CONTENTS......Page 8
Preface......Page 14
Introduction: Poffenberger’s Simple Reaction Time Paradigm for Measuring Interhemispheric Transfer Time......Page 18
I ANATOMY AND MORPHOMETRY OF THE CORPUS CALLOSUM......Page 26
1 Callosal Axons and Their Development......Page 28
COMMENTARY 1.1 The Effects of Early Injury to the Cortical Plate on Callosal Connectivity......Page 44
COMMENTARY 1.2 Binocular Input Elimination and the Reshaping of Callosal Connection......Page 47
2 Corpus Callosum Morphology in Relation to Cerebral Asymmetries in the Postmortem Human......Page 50
COMMENTARY 2.1 Complexity of Human Interhemispheric Connections......Page 64
3 Brain Size: A Possible Source of Interindividual Variability in Corpus Callosum Morphology......Page 68
COMMENTARY 3.1 Size Differences in the Callosum: Analysis Beyond the Main Effects......Page 81
COMMENTARY 3.2 Individual Differences in Corpus Callosum Morphometry: To Normalize or Not to Normalize for Brain Size......Page 87
4 Morphometrics for Callosal Shape Studies......Page 92
5 Mapping Structural Alterations of the Corpus Callosum During Brain Development and Degeneration......Page 110
EDITORIAL COMMENTARY 1 New Insights in Callosal Anatomy and Morphometry......Page 160
II PHYSIOLOGICAL ASPECTS OF CALLOSAL SENSORIMOTOR INTEGRATION......Page 166
6 Functions of the Corpus Callosum as Derived from Split-Chiasm Studies in Cats......Page 168
COMMENTARY 6.1 The Midline Fusion Hypothesis Is All Right But Cannot Explain All Callosal Functions......Page 183
7 Forebrain Commissures: Glimpses of Neurons Producing Mind......Page 186
COMMENTARY 7.1 From the Physiology of Callosal Connections to the Understanding of the Mind: Still a Long Way to Go......Page 195
8 Interhemispheric Visuomotor Activation: Spatiotemporal Electrophysiology Related to Reaction Time......Page 200
COMMENTARY 8.1 Interhemispheric Transfer of Visual Information as a Function of Retinal Eccentricity: Evidence from Event-Related Potentials......Page 249
COMMENTARY 8.2 Neuroimaging Patterns of Intra- and Interhemispheric Connectivity......Page 253
COMMENTARY 8.3 The Use of Event-Related Potentials for Measuring Interhemispheric Transfer Time......Page 259
EDITORIAL COMMENTARY 2 Current Directions in Physiological Studies of Callosal Functions......Page 261
III INTERHEMISPHERIC SENSORIMOTOR INTEGRATION: BEHAVIORAL STUDIES......Page 264
9 The Evolution of the Concept of Interhemispheric Relay Time......Page 266
COMMENTARY 9.1 Does the CUD in SRT Measure IHTT? Or: Is the Crossed-Uncrossed Difference in the Simple Reaction Time Task a Pure Measure of Interhemispheric Transfer Time?......Page 288
COMMENTARY 9.2 Interacting Hemispheres: A Means of Modulating Attention......Page 296
10 The Corpus Callosum Equilibrates Hemispheric Activation......Page 300
COMMENTARY 10.1 A Plan for the Empirical Evaluation of the Coactivation/Equilibration Model of Callosal Function......Page 311
11 Effects of Partial Callosal and Unilateral Cortical Lesions on Interhemispheric Transfer......Page 316
COMMENTARY 11.1 Interhemispheric Transfer of Visuomotor Inputs in a Split-Brain Patient: Electrophysiological and Behavioral Indexes......Page 325
12 Stable and Variable Aspects of Callosal Channels: Lessons from Partial Disconnection......Page 330
COMMENTARY 12.1 Attentional Modulation of Interhemispheric Transfer: A Two-Channel Threshold Model......Page 336
13 Sensorimotor Integration in the Split Brain......Page 348
COMMENTARY 13.1 Water Under the Bridge: Interhemispheric Visuomotor Integration in a Split-Brain Man......Page 366
14 Parallel Processing in the Bisected Brain: Implications for Callosal Function......Page 370
COMMENTARY 14.1 In Search of Lost Time: Functional SignifIcance of Crossed-Uncrossed Differences in Callosal Patients......Page 384
15 Agenesis of the Corpus Callosum......Page 386
COMMENTARY 15.1 Sensorimotor Interaction in Agenesis of the Corpus Callosum......Page 399
COMMENTARY 15.2 Cerebral Plasticity in Callosal Agenesis Versus Callosotomy......Page 401
COMMENTARY 15.3 Interhemispheric and Intrahemispheric Mechanisms of Visuomotor Integration in allosal Agenesis......Page 405
EDITORIAL COMMENTARY 3 Current Directions in Behavioral Studies of Callosal Functions......Page 410
IV THE CORPUS CALLOSUM AND CLINICAL INVESTIGATIONS......Page 418
16 Clinical Neuropsychological Assessment of Callosal Dysfunction: Multiple Sclerosis and Dyslexia......Page 420
COMMENTARY 16.1 Interhemispheric Conduction Delay in Multiple Sclerosis......Page 436
COMMENTARY 16.2 Redundancy Gain as a Measure of Implicit Sensorimotor Integration......Page 442
17 Alexithymia as a Consequence of Impaired Callosal Function: Evidence from Multiple Sclerosis Patients and Normal Individuals......Page 444
18 Functional Consequences of Changes in Callosal Area in Tourette’s Syndrome and Attention Deficit/Hyperactivity Disorder......Page 452
19 Using the Corpus Callosum as an Effective Anatomical Probe in the Study of Schizophrenia......Page 462
20 Interhemispheric Abnormalities in Schizophrenia and Their Possible Etiology......Page 474
EDITORIAL COMMENTARY 4 Current Directions in Clinical Studies of Callosal Functions......Page 482
V FROM ANATOMY TO BEHAVIOR: THE CASE OF PURE ALEXIA......Page 488
21 The Role of Homotopic and Heterotopic Callosal Connections in Humans......Page 490
COMMENTARY 21.1 Learning to Read and Write Shapes the Anatomy and Function of the Corpus Callosum......Page 502
22 Optic Aphasia and Pure Alexia: Contribution of Callosal Disconnection Syndromes to the Study of Lexical and Semantic Representation in the Right Hemisphere......Page 508
COMMENTARY 22.1 Right Hemisphere Contributions to Word Recognition in Pure Alexia......Page 526
COMMENTARY 22.2 Right Hemisphere Contributions to Residual Reading in Pure Alexia: Evidence from a Patient with Consecutive Bilateral Strokes......Page 529
COMMENTARY 22.3 Letter-by-Letter Reading: Regional Cerebral Blood Flow Correlates......Page 536
EDITORIAL COMMENTARY 5 The Case Study of Pure Alexia: Sensorimotor Integration in the Split Brain......Page 544
About the Authors......Page 552
Contributors......Page 558
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