VISUAL SYSTEM ORGANIZATION & DEVELOPMENT

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The overall aim of the research is to understand the functional contribution of parallel pathways originating in the retina to cortical visual areas. The proposal represents a continuation of studies on parallel processing in three identified channels in the visual system of the prosimian primate, galago. The four specific aims outlined here will investigate details of the transformation of visual information in the lateral geniculate nucleus (LGN) and striate cortex. In Aim I, studies are proposed that will examine the role of the W-like cell pathway in the LGN (which is well developed in galagos). Cluster analyses will be performed to determine subtypes of LGN W-like cells based on receptive field properties. Changes in W-like receptive field properties will be examined following activation or inactivation of collicular neurons to determine the role of this pathway. In Aim II, we propose studies on the role of the W-like cell pathway in striate cortex. Receptive field properties of cells in the cytochrome oxidase "blobs" in layer III will be examined to determine if these cells reflect a physiological signature of their LGN W-like cell input. Changes in the properties of the cortical "blob" cells will aso be examined following inactivation of the LGN layers. In Aim III, cells in striate cortical layers IV alpha and IV beta will be examined to determine if a physiological signature can be established that reflects their parvocellular (X-lik) and magnocellular (Y-like) LGN inputs. Anatomical connections of cortical layers IV alpha and IV beta will also be analyzed. Finally, in Aim IV, the extraretinal and intrageniculate modulation of parallel channels in the LGN will be studed by analyzing the distribution and source of non-retinal inputs and details of cholinergic transmission.