VISUAL SYSTEM ORGANIZATION AND DEVELOPMENT

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The overall aim of the research is to understand how parallel pathways from retina to cortex are organized and developed in primates. The proposal represents a continuation of studies on the organization and maturation of X-, Y-, and W-like information channels. The three Specific Aims outlined will investigate the adult distinguishing features and postnatal maturation of these pathways. In Aim I, studies are proposed to confirm and expand knowledge of the basic physiologic and morphologic divisions within the pathways from retina to striate cortex in adult galagos. Receptive field properties of retinal ganglion cells will be examined and compared to those of cell subclasses within the lateral geniculate nucleus (LGN) to determine how information is transformed. The morphology of retinal ganglion cells, LGN cells, and their afferents will be investigated for distinguishing features that correlate with the physiology. Change in W-like LGN cell receptive field properties will also be examined following inactivation of tectal neurons to determine the role of this pathway. Aim II will examine the development of features uncovered in Specific Aim I as a means of better understanding the adult organization. Studies are outlined that will investigate the maturation of LGN physiology and morphology. Finally, Aim III will test the iplications of hypotheses derived from galago data by comparative studies on galago and two other primate species selected for their distinctive visual system chacteristics. In these studies, cortical visual evoked potentials will be used to define the effect of inactivation of either the parvocellular or magnocellular LGN layers on spatial and temporal contrast sensitivity. Results of these studies should not only add to our understanding of the roles of these channels in vision but also to knowledge about their potential vulnerability to altered postnatal experience.