A study on the perception mechanisms of the retina with a computational and a physiological approaches.

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The purpose of this project was to elucidate the function of retinal neuronal network from the physiological and computational point of views. The following results were obtained in this project. 1).A linear analog network model was proposed to describe the neuronal circuit of the outer retina. 2).Using the model, we characterized the spatial filtering properties of the circuit in terms of the standard regularization theory, in which the early vision problems are attributed to minimization of a cost function. 3).A optical stimulator system was designed to measure the response properties of amacrine cells. The intracellular recordings were obtained from amacrine cells. A relation between the receptive field properties and the morphology of amacrine cells has been studied. 4).The intracellular concentration of Ca^<2+> was measured using fura-2 ratiometric method in isolated horizontal cells to study the Ca^<2+> regulation mechanism. 5).Two pathways of Ca^<2+> influx, i.e. the voltage-gated Ca^<2+> channels as well as the glutamate-gated channels were found. 6).The Na^+ -Ca^<2+> exchange and Ca^<2+> -ATP pump were found to extrude the intracellular Ca^<2+>.7).The results obtained in 5 and 6 suggested that the Ca^<2+> extrusion systems are also play important roles in shaping the light-evoked response in the horizontal cell. A computational study is now undertaken to elucidate this point.