| Our research is directed at understanding cellular mechanisms of information processing and cell-to-cell communication in the mammalian visual system. We currently study the structure and function of retinal amacrine cells. These cells are placed strategically to influence the response properties of the postsynaptic ganglion cells, thus helping to determine the visual information carried by the final output pathway of the retina to higher brain centers. Using electrophysiological and morphological labeling techniques, we want to elucidate the different response properties expressed by amacrine cells and correlate these with their cellular morphologies. Recently, we discovered that amacrine cells express complex response properties, such as orientation and direction sensitivity. These new findings dispute long-held ideas about the function of amacrine cells and suggest new patterns of retinal synaptic circuitry. We also use steady-state cable theory to create computational models of electrical current flow within the dendritic arbors of amacrine cells. These models examine how synaptic current is propagated and integrated within cells to form their light-evoked responses. We also study electrical coupling between retinal neurons. Using newly discovered biotinylated tracers which pass through gap junctions, we can now label and visualize groups of coupled cells which interact electrically. Our recent data indicate that communciation between neurons via electrical coupling is prevalent in mammalian retina and appears highly plastic. We are investigating how changes in stimulus conditions, such as the state of light adaptation, influence the degree of coupling between cells.
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