Eric Kandel - In Search of Memory.pdf - Neurobiologia - Eroza800

IN SEARCH OF

MEMORY

The Emergence of a New Science of Mind

ERIC R. KANDEL

ISBN 0-393-05863-8

POUR DENISE

CONTENTS

Preface xi

ONE

1. Personal Memory and the Biology of Memory Storage 3

2. A Childhood in Vienna 12

3. An American Education 33

TWO

4. One Cell at a Time 53

5. The Nerve Cell Speaks 74

6. Conversation Between Nerve Cells 90

7. Simple and Complex Neuronal Systems 103

8. Different Memories, Different Brain Regions 116

9. Searching for an Ideal System to Study Memory 135 10. Neural Analogs of Learning 150

THREE

11. Strengthening Synaptic Connections 165

12. A Center for Neurobiology and Behavior 180

13. Even a Simple Behavior Can Be Modified by Learning 187

14. Synapses Change with Experience 198

15. The Biological Basis of Individuality 208

16. Molecules and Short-Term Memory 221

17. Long-Term Memory 240

18. Memory Genes 247

19. A Dialogue Between Genes and Synapses 201

FOUR

20. A Return to Complex Memory 279

21. Synapses Also Hold Our Fondest Memories 286

22. The Brain's Picture of the External World 295

23. Attention Must Be Paid! 307

FIVE

24. A Little Red Pill 319

25. Mice, Men, and Mental Illness 335

26. A New Way to Treat Mental Illness 352

27. Biology and the Renaissance of Psychoanalytic Thought 363

28. Consciousness 376

SIX

29. Rediscovering Vienna via Stockholm 393

30. Learning from Memory: Prospects 416

Glossary 431

Notes and Sources 453

Acknowledgments 485

Index 489

PREFACE

Understanding the human mind in biological terms has emerged as the central challenge for science in

the twenty-first century. We want to understand the biological nature of perception, learning, memory,

thought, consciousness, and the limits of free will. That biologists would be in a position to explore

these mental processes was unthinkable even a few decades ago. Until the middle of the twentieth

century, the idea that mind, the most complex set of processes in the universe, might yield its deepest

secrets to biological analysis, and perhaps do this on the molecular level, could not be entertained

seriously.

The dramatic achievements of biology during the last fifty years have now made this possible. The

discovery of the structure of DNA by James Watson and Francis Crick in 1953 revolutionized biology,

giving it an intellectual framework for understanding how information from the genes controls the

functioning of the cell. That discovery led to a basic understanding of how genes are regulated, how

they give rise to the proteins that determine the functioning of cells, and how development turns genes

and proteins on and off to determine the body plan of an organism. With these extraordinary

accomplishments behind it, biology assumed a cen-

tral position in the constellation of sciences, one in parallel with physics and chemistry.

Imbued with new knowledge and confidence, biology turned its attention to its loftiest goal, understanding the

biological nature of the human mind. This effort, long considered to be prescientific, is already in full swing.

Indeed, when intellectual historians look back on the last two decades of the twentieth century, they are likely to

comment on the surprising fact that the most valuable insights into the human mind to emerge during this period

did not come from the disciplines traditionally concerned with mind—from philosophy, psychology, or

psychoanalysis. Instead, they came from a merger of these disciplines with the biology of the brain, a new

synthesis energized recently by the dramatic achievements in molecular biology. The result has been a new

science of mind, a science that uses the power of molecular biology to examine the great remaining mysteries of

life.

This new science is based on five principles. First, mind and brain are inseparable. The brain is a complex

biological organ of great computational capability that constructs our sensory experiences, regulates our thoughts

and emotions, and controls our actions. The brain is responsible not only for relatively simple motor behaviors,

such as running and eating, but also for the complex acts that we consider quintessentially human, such as

thinking, speaking, and creating works of art. Looked at from this perspective, mind is a set of operations carried

out by the brain, much as walking is a set of operations carried out by the legs, except dramatically more

complex.

Second, each mental function in the brain—from the simplest reflex to the most creative acts in language, music,

and art—is carried out by specialized neural circuits in different regions of the brain. This is why it is preferable

to use the term "biology of mind" to refer to the set of mental operations carried out by these specialized neural

circuits rather than "biology of the mind," which connotes a place and implies a single brain location that carries

out all mental operations.

Third, all of these circuits are made up of the same elementary signaling units, the nerve cells. Fourth, the neural

circuits use specific molecules to generate signals within and between nerve cells. Finally, these specific

signaling molecules have been conserved—retained as it

were—through millions of years of evolution. Some of them were present in the cells of our most

ancient ancestors and can be found today in our most distant and primitive evolutionary relatives:

single-celled organisms such as bacteria and yeast and simple multicellular organisms such as worms,

flies, and snails. These creatures use the same molecules to organize their maneuvering through their

environment that we use to govern our daily lives and adjust to our environment.

Thus, we gain from the new science of mind not only insights into ourselves—how we perceive, learn,

remember, feel, and act—but also a new perspective of ourselves in the context of biological

evolution. It makes us appreciate that the human mind evolved from molecules used by our lowly

ancestors and that the extraordinary conservation of the molecular mechanisms that regulate life's

various processes also applies to our mental life.

Because of its broad implications for individual and social well-being, there is now a consensus in the

scientific community that the biology of mind will be to the twenty-first century what the biology of

the gene was to the twentieth century.

In addition to addressing the central issues that have occupied Western thought since Socrates and

Plato first speculated about the nature of mental processes more than two thousand years ago, the new

science of mind gives us the practical insights to understand and cope with important issues about

mind that affect our everyday lives. Science is no longer the exclusive domain of scientists. It has

become an integral part of modern life and contemporary culture. Almost daily, the media report

technical information that the general public cannot be expected to understand. People read about the

memory loss caused by Alzheimer's disease and about age-related memory loss and try, often

unsuccessfully, to understand the difference between these two disorders of memory—one progressive

and devastating, the other comparatively benign. They hear about cognitive enhancers but do not quite

know what to expect from them. They are told that genes affect behavior and that disorders of those

genes cause mental illness and neurological disease, but they are not told how this occurs. And finally,

people read that gender differences in aptitude influence the academic and career paths that men and

women follow. Does this

mean there are differences between the brains of women and of men? Do men and women learn

differently?

In the course of our lives, most of us will have to make important private and public decisions that

involve a biological understanding of mind. Some of these decisions will arise in the attempt to

understand variations in normal human behavior, while others will concern more serious mental and

neurological disorders. It is essential, therefore, that everyone have access to the best available

scientific information presented in clear, understandable form. I share the view now current in the

scientific community that we have a responsibility to provide the public with such information.

Early in my career as a neuroscientist I realized that people without a background in science are as

eager to learn about the new science of mind as we scientists are to explain it. In this spirit, one of my

colleagues at Columbia University, James H. Schwartz, and I wrote Principles of Neural Science, an

introductory college and medical school textbook that is now entering its fifth edition. The publication

of that textbook led to invitations to give talks about brain science to general audiences. That

experience convinced me that nonscientists are willing to work to understand the key issues of brain

science if scientists are willing to work at explaining them. I have therefore written this book as an

introduction to the new science of mind for the general reader who has no background in science. My

purpose is to explain in simple terms how the new science of mind emerged from the theories and

observations of earlier scientists into the experimental science that biology is today.

A further impetus for writing this book came in the fall of 2000, when I was privileged to receive the

Nobel Prize in Physiology or Medicine for my contributions to the study of memory storage in the

brain. All Nobel laureates are invited to write an autobiographical essay. In the course of writing mine,

I saw more clearly than before how my interest in the nature of memory was rooted in my childhood

experiences in Vienna. I also saw more vividly, and with great wonder and gratitude, that my research

has allowed me to participate in a historic period of science and to be part of an extraordinary

international community of biological scientists. In the course of my work

I have come to know several outstanding scientists in the front ranks of the recent revolution in

biology and neuroscience, and my own research has been greatly influenced by my interactions with

them.

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