The final goal of this research, which began in 1968, is to produce a well-defined functional morphology of the vertebrate retina. We have developed a comprehensive methodology based on Wiener's theory of nonlinear analysis (white-noise analysis) and have accumulated a large body of data that characterize the morphology and physiology, including the response dynamics of neurons in the retina. The principal preparation used is the retina of the channel catfish. This current research proposal has three major aims: (1) Identification of neuronal circuitry in the inner retina. This is accomplished by injecting current into one neuron and by recording the evoked response, spike discharges or intracellular potential, form another neuron located nearby. Transfer functions will be obtained by a cross-correlation process. We expect to characterize three modes of transmission: very fast transmission mediated by electric coupling, fast (probably mono- synaptic) transmission and slow poly-synaptic transmission. (2) The functional connections will be referenced to the synaptic organization of the participating cells by injecting them with HRP and conducting electron microscopic observations of the nature and distribution of their synaptic connections. (3) Receptive fields. Neurons in the retina form a receptive field that changes in time and space. We will use three measures to explore receptive-field organization: (a) conventional stimuli consisting of either a combination of spot/annulus, drifting sinusoids, or a sweeping bar of light, (b) two input white-noise experiments to define dynamics of the receptive field center and surround, and (c) one-dimensional drifting white-noise grating. The results will be referenced against the neuronal connections in catfish retina. These three lines of inquiry will provide the basis for the development of a comprehensive view of the functional organization of the (cone-driven) neuron network in the inner retina.
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