A computational model of the spatiotemporal dynamics of retinal processing explains percepetual properties of visual persistence and afterimages
A computational model of retinal circuitry is developed to account for the stimulus duration, intensity, and spatial-frequency effects on visual persistence and afterimages. The model is based on contemporary neurophysiological evidence about the retinal network and reproduces some conventionally acclaimed retinal cell behaviors. Model simulations suggest that the stimulus effects on visual persistence are generated by suppression mechanisms that govern a short-term temporal scale light-gating process. This process, in its interaction with unique synaptic structures of each of the retinal cells, generates complicated patterns of spatiotemporal dynamics of retinal information processing that agrees with the perceptual phenomena in visual persistence. According to the model, the stimulus's effects on afterimages results from a long-term scale light adaption process mediated through horizontal cells. The same synaptic structures demonstrated in the short-term spatiotemporal dynamics similarly affect the perceptual properties of afterimages. Given the results from the retinal model, theoretical arguments are made to link the ideas of the retinal model with cortical processing models and to propose a coherent information processing scheme throughout retinal and cortical stages. The demonstrations of the retinal model and the theoretic discussions on the cortical processing models together suggest that the phenomenology of visual persistence and afterimages results from information processing spanning the entire visual system stream. Thus, these phenomena are potentially powerful tools to investigate retino-cortical spatiotemporal dynamics.^
Gregory Francis, Purdue University.