My long term goal is to understand the physiological mechanisms associated with human color vision. The cynomolgus monkey, which has color vision identical to that of normal human trichromats, will be the experimental animal. Micropipette electrodes filled with the marker enzyme horseradish peroxidase (HRP) will be used to record intracellularly from lateral geniculate axons terminating in the striate cortex. After physiologically characterizing a fiber, it will be injected iontophoretically with HRP to reveal its cortical terminations. Distinctive axonal arborization patterns will be correlated with specific function properties to better understand the significance of both the geniculate and the cortical layers in color processing. Intracellular recordings will be made from monkey striate cortical cells with HRP-filled micropipettes. The cells' physiological properties will be determined and then they will be injected with HRP. The study of the laminar positions, dendritic arborizations and axonal projections of functionally characterized color-sensitive cortical cells provides a most promising way to understand the intracortical circuitry for color processing, the synaptic connections and interactions involved, the integrative mechanisms leading to their receptive field construction and the development of their spectral sensitivities. Tungsten electrodes will be used to record extracellularly from single cells for long periods of time, as well as from many cells in a single experiment. The functional organization of the color cells in the monkey's striate cortex will be examined by making long, oblique electrode tracks through single cortical layers. The double opponent color cells in the supragranular blobs will be compared with those in layer 4, those in 4A will be correlated with those in 4Cb, upper versus lower 4Cb will be examined, and the more complicated color cells in the supragranular and infragranular layers will be contrasted. This approach will provide much useful information about the integrative steps involved in cortical color processing.
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