: Visual cortex in primates includes dozens of distinct areas arranged in a mosaic that occupies much of the cerebral cortex. This proposal will use physiological and anatomical methods to study form processing in the macaque monkey. In addition, anatomical and computerized brain mapping methods will be used to analyze and compare the arrangement of visual areas in humans and macaques. Experiments on form vision will involve recordings from neurons in visual areas V2 and V4 of the macaque. One project will analyze the spatial organization of classical receptive fields and nonclassical receptive field surrounds in area V2. The objective is to reveal neurophysiological mechanisms underlying the selectivity for textures and complex shapes that are encountered in many V2 neurons. A second project will determine whether surface features and object boundaries are analyzed by different neuronal populations in area V2 and whether neurons in V2 are directly implicated in specific aspects of form perception. A third project will study the representation of three-dimensional shapes in area V4. Neural responses to simulated bumps, indentations, and flat surfaces will be analyzed to determine whether cells in V4 explicitly represent the sign of surface curvature. The proposed comparisons of visual cortical areas in humans will make use of surface-based atlases and surface-based warping to deform the macaque map to the shape of the human cortical map. These comparisons will provide an objective basis for evaluating possible homologies between visual areas in the two species. Collectively, these experiments should reveal important principles of organization and function in primate visual cortex that are relevant to the understanding and treatment of functional deficits resulting from strokes and other neurological disorders.
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