FIGURE 9-26 On–Off Receptivity (A) In the receptive field of an RGC with an on-center and off-surround, a spot of light shining on the center excites the neuron, but a spot of light in the surround inhibits it. When the light in the surround is turned off, firing rate increases briefly—an offset response. A light shining in both the center and the surround would produce a weak increase in firing. (B) In the receptive field of an RGC with an off-center and on-surround, light in the center produces inhibition, light on the surround produces excitation, and light across the entire field produces weak inhibition.