The Neural Control of Vision
C. The Retina

The receptive fields of three major classes of retinal ganglion cellsThe receptive fields of retinal ganglion cells, as shown in Figure 4, are circular and are comprised of two regions, a central, excitatory one, and a concentric surround region that is typically inhibitory. As a result of this arrangement, a small spot of light confined to the center area produces a vigorous response in ganglion cells whereas a larger spot that impinges on both the center and the surround regions produces a much reduced response as will be shown later.