Sensory experience can powerfully alter the spatial and temporal organization of population codes in the brain throughout an animal's lifetime. In this dissertation I focus on how changes in sensory experience, by learning or environmental enrichment, alter sensory map topography in rodent primary sensory cortex. In Chapter 1 I review recent advances in our understanding of how perceptual learning and related sensory manipulations shape the structure of primary sensory cortex maps across multiple sensory modalities. Classic studies of map plasticity in primary sensory cortex have shown that experience shapes sensory tuning in individual neurons and at the average population level. But effective neural population codes depend on more than just sensory tuning in individual cells averaged over time. With population calcium imaging, activity can be measured simultaneously in large ensembles of neurons during behavior. This and related techniques make it possible to study changes in the single-cell level organization of sensory coding, as well as high-dimensional codes that depend on the activity of large ensembles of cells, and which may change with behavioral context. Here I review recent population calcium imaging and recording studies that have characterized population codes in sensory cortex, and tracked how they change with sensory manipulations and training on perceptual learning tasks. These studies confirm average sensory tuning changes observed in earlier studies, but also reveal other features of plasticity, including sensory gain modulation, restructuring of firing correlations, and differential routing of information to output pathways. Unexpectedly strong day-to-day variation exists in single-neuron sensory tuning, which stabilizes during learning. These are novel dimensions of plasticity in sensory cortex, which refine population codes during learning, but whose mechanisms are unknown. Most of what is known about how sensory experience shapes maps is based on studies that have used robust sensory manipulations, such as deprivation, chronic over-stimulation, or explicit pairing of a sensory stimulus with a reward or punishment, as in the studies discussed in Chapter 1. However, much less is known about how maps are refined by natural behavior-driven sensory experience. To understand how natural tactile experience influences map development, We studied the effects of tactile enrichment on the organization of the whisker map in mouse primary somatosensory cortex (S1), which is highly plastic throughout life and which contains an anatomically well-defined map of the whiskers. Mice were raised with enrichment (EN) or normal housing (CT) beginning at weaning (P21). We focused our study on Layer 2/3 (L2/3), which is particularly plastic and which has a “salt-and-pepper” organization of whisker tuning, and Layer 4 (L4), which contains the anatomical map of the whiskers. The genetically-encoded calcium indicator GCaMP6s was expressed virally in L2/3 or L4 excitatory cells using cell-type and layer-specific Cre mice. At P62 ± 13 days, we measured neuronal responses to 9 whiskers using 2-photon imaging through a chronic cranial window. After imaging was complete, cells were localized relative to anatomical barrel column boundaries corresponding to the whiskers in the stimulus set. Within a single anatomical column in both L2/3 and L4 excitatory cells, cells were heterogeneously tuned to different whiskers. Enrichment increased somatotopic precision (the fraction of cells within a certain radius that were anatomically tuned) in both layers near the centers of anatomical columns. Enrichment also sharpened whisker tuning curves in both layers, and essentially increased signal-to-noise of whisker coding in L2/3 by decreasing spontaneous activity while maintaining response magnitudes for columnar whiskers. In L2/3, point representations (the density and spatial spread of neurons responding to a whisker) were sharpened by increased whisker responses among cells located close to column centers. To study the impact of enrichment on the spatial and temporal structure of population coding, we compared pairwise noise and signal correlations in whisker-evoked activity within each column. In L2/3, signal correlations – which reflect overall tuning similarity – were similar in EN and CT for pairs within columns, though signal correlations were higher in EN for pairs located further apart. However, for pairs of neurons located across column boundaries but at similar distances, signal correlations were dramatically decreased in EN, while comparable to in-column levels in CT. In both groups, noise correlations – which reflect shared trial-by-trial variability that is independent of the stimulus – decreased sharply with distance between neurons. For pairs of cells across column boundaries in CT mice, signal and noise correlations exhibited the same relationships with inter-cell distance as within column pairs; however, In EN mice, cross-column signal and noise correlations were substantially reduced compared to in-column pairs. Essentially, enrichment induced reorganization of functional correlations along anatomical column boundaries. This suggests that enrichment may selectively alter connectivity and/or shared synaptic input according to column boundaries. These findings demonstrate a strong impact of juvenile sensory experience on functional columnar topography and organization in S1, and indicate that enrichment sharpens whisker representations at the population level in L2/3.

This solid introduction uses the principles of physics and the tools of mathematics to approach fundamental questions of neuroscience.

Investigation of the functional architecture of the human brain using modern noninvasive imaging techniques is a rapidly expanding area of research. A proper knowledge of methodology is needed to appreciate the burgeoning literature in the field. This timely publication provides an excellent catalogue of the main techniques. The authors offer an invaluable analysis of mapping strategies and techniques, providing everything from the foundations to the major pitfalls and practical applications of the modern techniques used in neuroimaging. Contains over 1000 full color pages with more than 200 color figures. Spanning the methodological gamut from the molecular level to the whole brain while discussing anatomy, physiology, and pathology, as well as their integration, Brain Mapping: The Methods, Second Edition, brings the reader a comprehensive, well-illustrated and entirely readable description of the methods for brain mapping. Drs. Toga and Mazziotta provide everything from the foundations to the major pitfalls and practical applications of the technique by assembling an impressive group of experts, all widely known in their field, who contribute an outstanding set of chapters.

How we raise young children is one of today's most highly personalized and sharply politicized issues, in part because each of us can claim some level of "expertise." The debate has intensified as discoveries about our development-in the womb and in the first months and years-have reached the popular media. How can we use our burgeoning knowledge to assure the well-being of all young children, for their own sake as well as for the sake of our nation? Drawing from new findings, this book presents important conclusions about nature-versus-nurture, the impact of being born into a working family, the effect of politics on programs for children, the costs and benefits of intervention, and other issues. The committee issues a series of challenges to decision makers regarding the quality of child care, issues of racial and ethnic diversity, the integration of children's cognitive and emotional development, and more. Authoritative yet accessible, From Neurons to Neighborhoods presents the evidence about "brain wiring" and how kids learn to speak, think, and regulate their behavior. It examines the effect of the climate-family, child care, community-within which the child grows.

This is the story of a hugely successful and enjoyable 25-year collaboration between two scientists who set out to learn how the brain deals with the signals it receives from the two eyes. Their work opened up a new area of brain research that led to their receiving the Nobel Prize in 1981. The book contains their major papers from 1959 to 1981, each preceded and followed by comments telling how and why the authors went about the study, how the work was received, and what has happened since. It begins with short autobiographies of both men, and describes the state of the field when they started. It is intended not only for neurobiologists, but for anyone interested in how the brain works-biologists, psychologists, philosophers, physicists, historians of science, and students at all levels from high school to graduate level.

This book presents a compelling unifying theory of which aspects of the brain are innate and which are not.

Almost all of the messages that are received by the cerebral cortex from the environment or from the body's internal receptors come through the thalamus and much current thought about perceptual processing is based on sensory pathways that relay in the thalamus. This volume focuses on three major areas: the role of thalamocortical communication in cognition and attention; the role of the thalamus in communication between cortical areas; the hypothesis that much or all of the information relayed by thalamus, even to classical, pure "sensory" areas of cortex, represents a corollary message being sent simultaneously to motor centers. It presents a broad overview of important recent advances in these areas. * Provides a look at brain structures involved in perception and action * Includes summaries by leading investigators in the field * Presents recent advances in our understanding of brain functions

This book focuses on associative memory cells and their working principles, which can be applied to associative memories and memory-relevant cognitions. Providing comprehensive diagrams, it presents the author's personal perspectives on pathology and therapeutic strategies for memory deficits in patients suffering from neurological diseases and psychiatric disorders. Associative learning is a common approach to acquire multiple associated signals, including knowledge, experiences and skills from natural environments or social interaction. The identification of the cellular and molecular mechanisms underlying associative memory is important in furthering our understanding of the principles of memory formation and memory-relevant behaviors as well as in developing therapeutic strategies that enhance memory capacity in healthy individuals and improve memory deficit in patients suffering from neurological disease and psychiatric disorders. Although a series of hypotheses about neural substrates for associative memory has been proposed, numerous questions still need to be addressed, especially the basic units and their working principle in engrams and circuits specific for various memory patterns. This book summarizes the developments concerning associative memory cells reported in current and past literature, providing a valuable overview of the field for neuroscientists, psychologists and students.

In the past decade neuronal plasticity has become a major theme of modern neurobiology, from cellular and molecular mechanisms of synapse formation in worms and insects to behavioural recovery from strokes in elderly humans. For this reason the focus of interest in the present volume of Progress in Brain Research is on the topic of neuroplasticity in mature organisms, including humans. Contributions range from neurogenesis and synaptic plasticity in the adult primate brain, to neural mechanisms of learning and memory, and the influence of environmental factors and aging on the functional potential of the central nervous system. Several contributions focus on recent developments in neural regeneration and brain repair, providing challenging evidence that the use of stem cell neurotherapy may be beneficial to humans suffering from various neurological and psychiatric diseases. This volume integrates new information on the cellular and molecular mechanisms of neuroplasticity and highlights challenging future questions in this exciting and topical area of neuroscience.

The brain ... There is no other part of the human anatomy that is so intriguing. How does it develop and function and why does it sometimes, tragically, degenerate? The answers are complex. In Discovering the Brain, science writer Sandra Ackerman cuts through the complexity to bring this vital topic to the public. The 1990s were declared the "Decade of the Brain" by former President Bush, and the neuroscience community responded with a host of new investigations and conferences. Discovering the Brain is based on the Institute of Medicine conference, Decade of the Brain: Frontiers in Neuroscience and Brain Research. Discovering the Brain is a "field guide" to the brainâ€"an easy-to-read discussion of the brain's physical structure and where functions such as language and music appreciation lie. Ackerman examines: How electrical and chemical signals are conveyed in the brain. The mechanisms by which we see, hear, think, and pay attentionâ€"and how a "gut feeling" actually originates in the brain. Learning and memory retention, including parallels to computer memory and what they might tell us about our own mental capacity. Development of the brain throughout the life span, with a look at the aging brain. Ackerman provides an enlightening chapter on the connection between the brain's physical condition and various mental disorders and notes what progress can realistically be made toward the prevention and treatment of stroke and other ailments. Finally, she explores the potential for major advances during the "Decade of the Brain," with a look at medical imaging techniquesâ€"what various technologies can and cannot tell usâ€"and how the public and private sectors can contribute to continued advances in neuroscience. This highly readable volume will provide the public and policymakersâ€"and many scientists as wellâ€"with a helpful guide to understanding the many discoveries that are sure to be announced throughout the "Decade of the Brain."