The cerebral cortex underwent a remarkable expansion in human evolution and is, by far, the largest part of the human brain. In order to facilitate research into cortical function, we propose to create, test, streamline, and make user-friendly a new cortical mapping system designed to preserve the physical layout of the cerebral cortex, which is most accurately described as a thin, folded, two-dimensional sheet. Most previous methods have mapped the cerebral cortex and other brain structures using a volume-based system with three coordinates for each point instead of two. Volume-based systems are straightforward to apply, and they generalize to non-cortical structures. However, there are a number of fundamental advantages to using a surface-based system for mapping the cerebral cortex. Preliminary results indicate that surface-based mapping yields improved inter subject comparisons. In addition, it enables many new surface-based computations as well as providing a unified, user-comprehensible way to display the constantly growing and paradigmatically diverse corpus of brain imaging data. To make it possible to exploit the advantages of both two- and three-dimensional approaches, we show how to generate a precise mapping between these two systems. We demonstrate many of the components of the proposed surface-based analysis and visualization software to show that most of the ideas are already prototyped. A number of our recent papers using this software further illustrate its usefulness in brain-mapping. In this proposal, we first plan to automate, optimize, and validate our existing software, while expanding a surface-based brain mapping database. The database will consist of (1) structural magnetic resonance images and cortical surface reconstructions made from them, and (2) functional magnetic resonance images analyzed in a surface-based framework both taken from the same normal human subjects. This database will be used to construct an averaged """"""""canonical"""""""" human cortical surface, with much less """"""""blurriness"""""""" than current 3-D-averaged brains. This database will also be used to implement and validate a novel 2-D latitude and longitude coordinate system for the unfolded cortical surface. The software tools will be ported to several platforms, including SGI, Sun and PC (Linux), in order to facilitate their dissemination to the wider scientific community.
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