A layered model for visual processing in avian retina.

Visual processing in avian retina is interpreted by means of a layered model in which: a) outer layers provide with spatio temporal fast and retarded versions of the stimuli incident on the retina; a possibility is that horizontal cells are involved in isotropically generating the retarded version which is transversally translated; b) prominent specialization of ganglion cells is the result of local non-linear lateral interaction at the inner plexiform layer, mediated by amacrines which return, also isotropically, the translated retarded signals. Small though systematic deviations in the sites of the lateral interaction result in anisotropic but uniform receptive fields for some ganglion cells. A simple though general expression for the model is derived which includes the various types of recorded avian ganglion retinal cells responses, which also permits a unified interpretation of visual processing in avian and cat's retinae.