Inhibitory mechanisms within the receptive fields of X-and Y-type retinal ganglion cells of the cat (author's transl)]

Two-stages of the inhibitory mechanisms were assumed within the on-center receptive field (RF) of the cat's retinal ganglion cell on the basis of the following two experiments: 1) Effect of background intensity upon the magnitude of the response to the RF-centered spot of stimulus, and 2) the time course of the inhibitory effect when the additional spot of light is presented in the same RF center region. The first stage is an inhibitory feed-back from horizontal cell to the photoreceptor. Both X-and Y-fields have this feed-back route. By this gain control machanisms, the ganglion cell will respond to the intensity ratio of the spot to the backgound. The second stage of inhibitory mechanism in X-field is the feed-back from sustained amacrine cell to the bipolar cell. Above two stages of feed-back mechanism in X-field explain the strong maintained suppressive effect produced by the additional spot of light. On the other hand, the Y-type ganglion cell will recive the inhibitory input via feed-forward path from trannsient amacrine cell. This explains the transient on- and of f-suppressive effects