Correlation Among Retinal Directionally Selective Cells

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DESCRIPTION (From the Applicant's Abstract): A central problem in visual neuroscience is the binding problem. How does the brain know that it has to bind the responses of neurons with small visual windows to obtain coherent pictures of large objects? One long-term goal of the proposed research is to elucidate the retinal mechanisms underlying visual binding. Three hypotheses for these mechanisms involve gap junctions between ganglion cells, and common cholinergic, glutamatergic, and GABAergic synapses. Four specific aims will test these hypotheses in directionally selective ganglion cells of turtles and rabbits, since evidence of long-contour binding exists for these cells: 1)This aim will test whether millisecond correlation could code long, moving contours by recording simultaneously from neighbor directionally sensitive cells with electrophysiological techniques. 2)The experiments here will use simultaneous electrophysiological recordings and pharmacology to test the GABA, acetylcholine, glutamate, and gap-junction hypotheses of retinal correlation. 3)Specific aim 3 will study whether long-range correlation takes place by mapping the population of directionally selective cells with live Ca2+fluorescence. 4)Finally, the last aim will test a prediction of the cholinergic hypothesis for correlation by measuring acetylcholine release following motion adaptation with high performance liquid chromatography. The study of binding may have important health relevance. Schizophrenia patients, for instance, cannot detect contours in tasks relying on long-range spatial interactions of orientational signals. And the integration of orientation information across space is impaired in amblyopia. Retinal binding defects may contribute to some of these integrative problems, but even if not, retinal strategies and mechanisms may shed light on mechanisms in other areas of the brain.