The overall goal of this project is to increase the understanding of the systems-level organization of vision and visuomoter behavior by studying subjects with brain lesions and using visual psychophysics as the main approach. The neural basis of human vision is commonly discussed in terms of a """"""""what"""""""" pathway extending from the ventral bank of calcarine fissure to the temporal cortices and a """"""""where"""""""" pathway extending from the dorsal bank of the calcarine fissure to the parietal cortices. Growing evidence indicates that some visual mechanisms depend on the processing of signals the visual cortices proper. Pathways for object vision and visuospatial processing appear to connect with prefrontal areas involved in visual memory and attention, and with cerebellar mechanisms that support motion parallax and perception of form-from-temporal- structure. Because the organization of these mechanisms is critical to our understanding of human vision, we propose to investigate them during the next funding period in a series of hypothesis-driven experiments. Experiments on for-from-temporal structure will assess neural mechanisms for recovering global spatial structure of objects form visual elements undergoing raid, irregular change. Experiments on mental rotation will help distinguish between neural mechanisms for visual motion and movement imagery. Testing of motion parallax will distinguish between mechanisms that use, head, eye, and retinal motion signals for perception of for perception of object structure and depth. Experiments using Sternberg's visual recognition task will help bridge the gap between the psychophysics of visual form perception and memory. Studies of attention will investigate top-down and bottom-up mechanisms that affect visual search and object recognition. Studies of reaching will elucidate neural mechanisms for planning and executing hand movements to targets amid distracters. The proposed experiments capitalize on novel results and techniques from the current funding period. Data gained from these studies of the neural basis of visual function could also help guide future strategies for rehabilitation, optimal display of visual information, and mitigation of injury risk from car crashes and falls in neurological patients with higher visual dysfunction.
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