Distribution of Excitation and Inhibition in Receptive Fields of Lateral Geniculate Neurones

Abstract

IT has become apparent that the composition of receptive fields of cells in the visual system vary considerably with the species studied, the level in the visual system examined and the stimulus parameters used. In spite of this variability, one characteristic form of receptive field has frequently been found at low levels in the visual system. It is usually described as roughly circular in shape and is made up of concentric zones which have the same spectral sensitivity. The important features of a unit with such a receptive field are that light stimulation in the centre of the field leads to either an increase or decrease in the cell's rate of discharge, while stimulation in the surround leads to a rate change in the opposite direction. If both of these regions are stimulated together, the resultant response is a combination of the separate responses of the regions¹. Thus it appears that at some peripheral point there is a combination of inputs so that the response of the cell indexes the amount of activation received by an excitatory system minus the amount of activation received by an inhibitory system.