ANALYSIS OF STRUCTURE-FROM-MOTION IN VISUAL CORTEX

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DESCRIPTION: (Adapted from the Investigator's Abstract): This proposal undertakes the first systematic analysis of the cortical topography of area 7a of the inferior parietal lobule in the behaving monkey. The focus is on uncovering the distribution of multiple visual, oculomotor and spatial representations across the extent of area 7a. An innovative combination of intrinsic optical imaging, single unit recordings and anatomical tracer methods will be used to address these issues at multiple levels of resolution. Understanding of area 7a in the inferior parietal lobule of the monkey is beginning to plateau. It is well established from single unit studies that area 7a neurons represent visual and eye position information, as well as attentional state. However little is known as to how these properties are distributed across the cortex, or how these distributed representations are modified by behavior. Spatial representations in area 7a: To explore these issues, optic flow (e.g. radial, planar rotational, translation) and luminance stimuli will be presented while the animal fixates on different locations in the visual field in a reaction time task. Many qualities that alter the response of area 7a neurons, such as speed and disparity, and vergence will be systematically manipulated to determine the dependence of the distributed representations. Optical imaging of the intrinsic signal will be used to map the topography of retinal, eye position, and head-centered location across the cortical surface in the behaving monkey. Single unit studies will be used to verify the results of the optical imaging. The relationships between both associational and collosal projections and the optically recorded maps will be determined to verify the maps themselves, as well as to understand how the distributed signals are transmitted to recipient areas. Attentional modulation of maps: The monkeys'attentional state will be altered to determine whether the cortical representation is plastic, i.e. it can be transformed across the cortical surface. The combination of optical measurements, single unit recording, and anatomy allows characterization of normal parietal spatial function. These studies will be crucial in correctly choosing which parietal representations are best modified through therapy when there are spatial deficits in human subjects caused by parietal damage through stroke.