Brains as Engines of Association: An Operating Principle for Nervous Systems

217 Pages·2019·101.949 MB·English

by  Dale Purves

Brains as Engines of Association

Brains as Engines
of Association
AN OPERATING PRINCIPLE FOR
NERVOUS SYSTEMS
Dale Purves
1
1
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Library of Congress Cataloging- in- Publication Data
Names: Purves, Dale, author.
Title: Brains as engines of association : an operating principle for nervous systems /
Dale Purves.
Description: New York, NY : Oxford University Press, [2019] |
Includes bibliographical references and index.
Identifiers: LCCN 2018035410 | ISBN 9780190880163
Subjects: LCSH: Brain. | Neurobiology. | Neural circuitry.
Classification: LCC QP356.25 .P86 2019 | DDC 612.8/ 2— dc23
LC record available at https://l ccn.loc.gov/ 2018035410
9 8 7 6 5 4 3 2 1
Printed by Sheridan Books, Inc., United States of America
CONTENTS
Preface ix
Acknowledgments xiii
What Nervous Systems Do for Animals
PART I }
1. Putting the Question in Perspective 3
Introduction 3
Life on Earth 3
Defining Life 5
Energy 6
Evolution 7
Mechanisms 8
Teleology 10
Conclusion 11
Suggested Reading 11
2. Organisms Without Nervous Systems 13
Introduction 13
Bacteria 13
Protists 16
Plants 18
The General Strategy 21
Conclusion 21
Suggested Reading 21
3. Organisms With Nervous Systems 23
Introduction 23
Defining Nervous Systems 23
The Emergence of Nervous Systems 26
The Emergence of Central Nervous Systems 28
What Do Brains Add? 28
Conclusion 33
Suggested Reading 33
vi { Contents
Nervous Systems as Engines of Association
PART II }
4. The Organization of Nervous Systems 37
Introduction 37
Stimuli 37
Preneural Processing 38
Neural Processing 39
Behavioral Output 43
Neural Systems and Subsystems Are Interactive 45
Conclusion 47
Suggested Reading 47
5. The Problem 48
Introduction 48
Vision as an Example 49
The Basic Challenge 49
An Answer in General Terms 51
Qualia Determined by Empirical Ordering 54
Perceptual Discrepancies 54
Mechanisms 55
Other Modalities 56
Conclusion 57
Suggested Reading 58
6. Neural Associations 59
Introduction 59
Associations Wrought by Evolution 59
Associations Wrought by Lifetime Learning 61
Associations Wrought by Culture 65
Behavioral Categories of Associations 67
Reward 68
Behavioral Responses as Reflexes 69
What Is Associated? 70
Counterarguments 70
Conclusion 71
Suggested Reading 71
Evidence that Neural Systems Operate Empirically
PART III }
7. Evidence from Lightness and Color 75
Introduction 75
Luminance and Lightness 75
Analyzing the Occurrence of Luminance Patterns 78
Effects of Other Luminance Patterns 80
Contents } vii
Spectral Energy and Color 84
The General Strategy 86
Conclusion 88
Suggested Reading 88
8. Evidence from Geometry 89
Introduction 89
Seeing Intervals 89
Seeing Angles 93
Seeing Object Sizes in Two Dimensions 96
Seeing Object Sizes in Three Dimensions 97
Seeing Stereo Depth 100
Conclusion 103
Suggested Reading 103
9. Evidence from Motion 104
Introduction 104
Apparent Motion 104
The Perception of Speed 106
Implications for the Perception of Time 110
The Perception of Direction 112
Conclusion 115
Suggested Reading 115
10. Evidence from Audition 117
Introduction 117
Sound Signals 117
Sources of Tones 118
Sound Signal Spectra 119
The Problem in Audition 120
An Empirical Approach 122
Evidence from Speech 123
Evidence from Music 127
Implications for Any Sensory System 129
Conclusion 129
Suggested Reading 130
Alternative Concepts of Neural Function
PART IV }
11. The Major Options 133
Introduction 133
Neural Function as Feature Detection 133
Neural Function as Statistical Inference 136
Neural Function as Predictive Coding 137
viii { Contents
Neural Function as Efficient Coding 138
Neural Function as Computation 140
Conclusion 143
Suggested Reading 143
12. Summing Up 145
Introduction 145
Obstacles and a Way Around Them 145
Empirical Ranking 146
Winning Games 147
Biological and Artificial Intelligence 148
Consequences for Neuroscience 150
The Status of Reasoning 152
Novel Situations 153
Choice 154
Culture 155
Frequency of Stimuli 155
Conclusion 156
Suggested Reading 156
Glossary 159
Bibliography 169
Index 187
PREFACE
This book concerns a question that has bothered me— and no doubt many others—
for a long time: What does the human brain and the rest of the nervous system
actually do?
Based on subjective experience, the question seems gratuitous: Isn’t the brain the
ultimate organizer of our behavior and the seat of the “I” when we think and act?
The term “behavior,” however, includes an enormous range of responses to internal
and external stimuli, and what “organizing” this welter of reactions means is not at
all clear. Likewise, what the “I” might be in this conception of neural function has
been debated for centuries without resolution.
If the goal of biology is to understand how living things succeed in the world
and the mechanisms they use to do so, then this sort of answer only papers over
our ignorance about the function of the nervous system compared to other organs.
By middle school, kids have learned that the respiratory system oxygenates the
blood, that the digestive system infuses blood with nutrients, that the cardiovas-
cular system conveys oxygen and nutrients to body tissues, and so on. An oper-
ating principle of one sort or another has been documented for every major organ
system save one: the brain and the rest of nervous system.1 Although textbooks and
an overwhelming original literature testify to the wealth of neurobiological infor-
mation gleaned over the past century or more, a comparable statement about the
nervous system will not be found.
This deficiency has led some investigators to imagine that the human brain is so
specialized that understanding it will require approaches that have not been needed
to fathom the operating principles of other organ systems. The implication is that
conventional anatomical and physiological thinking is not up to understanding
the human brain, sometimes described as “the most complex object in the known
Universe.”2 Some of the disciplines envisioned as coming to the rescue are com-
puter science, mathematics, statistics, network theory, game theory, graph theory,
cybernetics, systems engineering, cognitive psychology, physics, quantum physics,
philosophy, and “big data” mining. The big data approach (called “connectomics”)
rests on the idea that, if all else fails, documenting the connectivity of the estimated
1 The term “brain” is often used as if the rest of the nervous system doesn’t count for much. In fact,
there are about as many nerve cells in the spinal cord and peripheral nervous system as there are in the
cerebrum, cerebellum, and brainstem (the usual definition of the brain).
2 This truism was recently asserted by Christof Koch, chief scientific officer of the Allen Institute
for Brain Science (June 14, 2013, on NPR’s “Science Friday” with Ira Flatow). ix