The report presents both a way of looking at perceptual mechanisms in nervous systems in terms of distributed information processing, and a way of creating computer models of parts of nervous systems. The first notion views a nervous system as a collection of interacting parallel-operating computation units, each of which has some part of the total information entering through the system's receptors. The second idea presumes that a precise communicable model would be of aid to nervous system researchers and shows one way of using a serial digital computer to model a parallel operating nervous network. These ideas are incorporated in a model of the visual system of the frog. (Author/AL)