Extreme variations in callosal anatomy are found in normal and diseased populations. These variations complicate the design of systems to detect callosal anomalies in disease and to clarify associations between callosal structure and sex, handedness, and a variety of behavioral and cognitive factors.

In this chapter we have reviewed the perplexing variety of methods that are available for analyzing callosal structure. In view of the controversy over callosal differences and their determinants, probabilistic reference systems based on large human populations may help to identify group-specific patterns of callosal structure, providing a sample size appropriate to investigate subtle effects. Anatomical models can be combined with anatomically driven elastic transformations that associate homologous brain regions in a database of anatomical data. These strategies provide the ability to perform morphometric comparisons and correlations in three dimensions between a given subject's MR scan and a population database or between population subgroups stratified according to relevant clinical and/or demographic criteria.

In many ways, static representations of brain structure are ill suited to analyzing the dynamic processes of brain development and disease. The inherently changing morphology complicates attempts to compare callosal anatomy across subjects and groups, and interaction effects between age, sex, and other demographic factors are also observed. The intense interest in brain development and disease mandates the design of mathematical systems to track anatomical changes over time and map dynamic patterns of growth or degeneration. In this chapter we introduced an approach to mapping patterns of growth at the callosum, emphasizing the regional complexity of growth patterns over a prolonged period.

In the near future, brain-mapping techniques will provide the ability to map growth and degeneration in their full spatial and temporal complexity. In spite of the logistic and technical challenges, these mapping approaches hold tremendous promise for representing, analyzing, and understanding the extremely complex dynamic processes that affect regional anatomy in the healthy and diseased brain.

acknowledgments Paul Thompson was supported by the U.S. Information Agency, under Grant G-1-00001, by a Fellowship of the Howard Hughes Medical Institute, and by a research grant from the U.S.-U.K. Fulbright Commission, London. Additional support was provided by research grants from the National Library of Medicine (LM/MH05639), the National Science Foundation (BIR 93-22434), and the NCRR (RR05956) and by a Human Brain Project grant to the International Consortium for Brain Mapping, which is funded jointly by NIMH and NIDA (P20 MH/DA52176). Special thanks go to our colleagues Michael Mega, Jay Giedd, Roger Woods, David MacDonald, Colin Holmes, Keith Worsley, Alan Evans, and John Mazziotta, whose advice and support have been invaluable in these investigations.

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Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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