The long-range goal is to identify, in a non-human primate model, the structure and physiology of diverse retinal cell types, and to understand how retinal circuitry creates the parallel pathways of the visual system. The broad goal for the next project period is to characterize the morphology, physiology and central connections of newly identified color-, motion- and intrinsically photosensitive ganglion cell types. To accomplish these goals we will first apply a new method termed 'retrograde photodynamics' to the macaque retina to link physiology, anatomy and central connectivity of novel ganglion cell types. Second, we will apply a new method of optical imaging of light-evoked dendritic calcium signals to ganglion cell types in vitro to determine how L-, M- and S-cone inputs to specialized dendritic structures signal color. The proposed research has 4 specific aims: 1) To determine the visual response properties of novel LGN-projecting ganglion cell types. We will test the hypothesis that newly identified large mono- and bistratified cells code for color. 2) To determine the visual response properties of novel ganglion cell types that project to the superior colliculus. We will test hypothesis that the recursive monostratified and bistratified types are the origin ON- and ON-OFF-direction selective signals in primate. 3) To determine the anatomy, physiology and central connections of a unique population of melanopsin-containing, photoreceptive ganglion cells. 4) To determine the cone specificity of light-evoked calcium signals in the dendrites of color opponent ganglion cells. We will test the hypothesis that cone-type selective input to dendritic tree components of the large bistratified cells is the key mechanism for 'red-green' color opponency. Many aspects of macaque visual pathway organization are comparable to human; our results therefore will contribute to the best and most detailed structure-function model of the cell types of the human retina and visual pathways. Until now the majority of diverse primate ganglion cell types have been inaccessible to detailed physiological and anatomical analysis and their function and relevance to human disease and visual disorders has remained unexplored. The proposed projects will clarify the retinal origins and circuits for color-, irradiance- and motion-sensitive pathways that underlie many aspects of visual performance, the cellular basis for psychophysical measures of vision and mechanisms by which retinal disease affects human vision.
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