The orderly topographic mapping of external visual stimuli onto the retina is the first step in our perception of a spatially coherent visual world. A major function of the retina is to process this map of spatial information; this processing is dependent on specific neuronal populations which are themselves distributed spatially throughout the retina. Since complex coding of specific aspects of the visual stimulus is first evident at the ganglion cell level, the neuronal populations that interact in the inner plexiform layer are of particular importance. At the present time, little is known about the spatial organization of these specific neuronal systems or how this organization is achieved. Immunohistochemical methods now available can provide complete morphological staining of all cells in a specific selected neuronal population. It is therefore possible to isolate populations of cells in flta-mounted retina in order to study their distribution, organization, dendritic branching patterns and dendritic coverage. Two immunohistochemical methods will be used in this study. The first employs antisera to tyrosine hydroxylase to label dopaminergic neurons (amacrine, displaced amacrine and interplexiform cells) in the retinas of rabbit, cat, and ferret. The second method is directed towards producing monoclonal antibodies that label rabbit retinal ganglion cells having specific morphologies. Since ganglion cell morphology and physiology are closely related in the rabbit retina, it is possible that isolating populations of cells having specific morphologies will also isolate classes of cells having specific physiological response properties. The spatial distribution and organization of the specific cell populations in adult retinas will be analyzed using spatial statistics; dentritic branching patterns and coverage will be characterized using quantitative morphometry. Computer simulations of cell distribution patterns and dendritic morphology will be used to generate hypotheses about developmental mechanisms that can then be tested experimentally by studying immature retinas. By the combined use of immunohistochemical and analytic methods, these studies are expected to reveal fundamental principles by which specific retinal information processing systems are organized and overlaid to provide the sampling system necessary for a spatially coherent visual world.
