Cover

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Title Page, Copyright Page, Dedication

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CONTENTS

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p. vii

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Introduction

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pp. 1-4

The United States Congress designated the 1990s as the Decade of the Brain, but some suggest that the twenty-first century will be the century of the brain, when the last great frontier in biology —an understanding of the most complex biological system, the human brain—will be breached. Already the considerable advances made in neuroscience...

Part I—The Developing Brain

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1 Building a Brain

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pp. 7-32

Understanding how the brain forms is one of biology’s greatest challenges. From a relatively few undifferentiated cells in the young embryo, all of the neurons and glial (supporting) cells arise. The adult human brain contains about 100 billion neurons (a conservative estimate) and perhaps 10 times as many glial cells. Because virtually all neurons...

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2 Maturing a Brain

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pp. 33-56

In the first chapter I described how the brain is formed—how precursor cells become specified as neurons, how these nascent neurons migrate to appropriate positions in the embryonic brain and then differentiate into specific neuronal subtypes. I discussed how axons find their way to their targets and, finally, how synapses are formed. These events establish the framework of the brain...

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3 Developing Behaviors

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pp. 57-80

In the last chapter I described the maturation of the brain and how experience molds it, primarily by pruning. Dendritic and axonal fields of neurons are refined, synapses rearranged, and neurons even lost. There are critical periods for much of this plasticity, sensitive times early in life when various aspects of brain structure and function are particularly susceptible to alterations. In this chapter I explore examples....

Part II—The Adult Brain

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4 Teaching Older Dogs New Tricks

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pp. 83-110

The previous two chapters emphasized the point, certainly correct, that the young developing brain is much more plastic than the adult brain. Indeed, in language and birdsong development as well as sound localization in owls, puberty or sexual maturation seems to be the point when critical developmental abilities are lost. And it is common experience that motor skills—riding a bicycle or even swinging a golf club—are much...

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5 Controversies: New Neurons and Genes and Behavior

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pp. 111-136

The previous chapter described various ways cortical circuitry can be modified—from simply altering the strength of synapses to neurons extending new branches and making new synapses. It deftly avoided one of the most contentious questions of the day: Can new neurons be generated in the adult mammalian brain? New neurons can be generated in nonmammalian brains, as I shall describe below, but what...

Part III—The Aging Brain

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6 Is Aging of the Brain a Disease?

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pp. 139-160

We have all witnessed the deterioration of our parents or grandparents as they aged. Too often, it is a sad deterioration with a loss of quality of life as they fail mentally. At the same time, we read about the marvelous advances in medicine that are supposed to make us healthier and live longer. What is going on? Are people living longer? And if so, what are the consequences? Is it likely that we could live to be 150 or...

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Conclusions (and Speculations)

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pp. 161-174

Neurobiological studies of the developing brain provide much information on how the brain initially forms in the fetus. At first glance, we might conclude that early brain development depends strictly on nature—intrinsic genetic directives—and Chapter 1 appears to support this view. But it is important to recognize that environment and nurture can also play a role in early brain development. I use the term...

Further Reading

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pp. 175-176

Figure Credits

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pp. 177-178

Index

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pp. 179-190