The focus of our research for the next five years will be to determine the functions of extrastriate visual cortical areas and how the neurons therein perform coding operations. Our ongoing work on rhesus monkeys suggests that extrastriate cortical areas did not evolve, as had been previously suggested, to separately analyze different basic aspects of vision such as color, depth, motion, form, and texture. Instead, many more extrastriate areas engage in higher-level analyses than had been thought. These areas co-process several visual attributes and have, in part, evolved to facilitate object recognition in three dimensional space and to recognize objects when they are partially occluded or are seen from different perspectives under various conditions of illumination. The ability to learn and store visual objects in memory is an essential part of this process. To test these hypotheses we plan to apply three kinds of experimental procedures in our research: (1) recordings with single and multiple electrodes to assess the response properties of neurons in extrastriate areas using three dimensional stimuli that are transformed in various ways, (2) chronic recordings with implanted electrode arrays to determine how the response properties of cells are altered during the process of learning new visual objects, and (3) assessment of the visual capacities of animals on a broad range of tests after the removal of selected extrastriate cortical areas. The proposed work has important clinical relevance as it will serve characterize the functions of various visual cortical areas.
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