Cortical Representation of the Visual Image

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DESCRIPTION (provided by applicant): This proposal concerns studies of the macaque monkey visual cortex (V1) where the receptive fields of many V1 neurons are made up of the classical receptive field (CRF) and regions beyond the classical receptive field (bCRF) that modulate the activity in the CRF. It has been proposed that the interaction between the two regions may contribute to figure-ground segregation, signaling of image junctions including boundary curvature and of integration of extended object boundaries. Some of these functions require modulation between the CRF and the region bCRF that is spatially global; others suggest modulation from spatially discrete regions around the CRF. For other functions such as contour integration response enhancement is predicted. Currently, there are conflicting findings and considerable debate as to whether all of these functions can be attributed to cells in V1. Based on preliminary studies we hypothesize that timing and spatial organization may be key in resolving a number of issues that are currently in dispute. The objective during the current grant period is to characterize the time evolution or "impulse response" of the interaction between the CRF and the region bCRF as a function of orientation and spatial location in the region bCRF. Our aim is to extend and unify current concepts and models concerning the modulatory influences from the region bCRF. Determining how the visual pathways encode the visual image provides that basis for understanding how these processes can be damaged and subsequently treated in visual disorders.