Fig. 7.

Light adaptation narrowed the total spatial inhibitory input to OFF bipolar cells under conditions with similar stimulus intensity steps. A and B: example L-IPSCs recorded from an OFF type 3 bipolar cell in dim and light intensity step-controlled conditions, black and gray traces, respectively (1-s flash of a 25-μm bar of light, −200, 0, and 200 μm away from the recorded cell). The dark-adapted (dim light) C_M = 0.995 (C_W = 483) and the light-adapted C_M = 0.971 (C_W = 67), where the step in stimulus intensity from the background was similar. Light adaptation greatly reduced L-IPSCs 200 μm away from the OFF bipolar cell and decreased the center L-IPSC. Light stimulus is indicated by gray disconnected bars under L-IPSCs; OFF type 3 bipolar cells respond at the offset of light. C: spatial inhibition curves of Q, normalized to the center bar stimulus, in dim- and light-adapted conditions (n = 4). The spatial inhibitory distribution became significantly narrower with light adaptation. D: L-IPSC Q, normalized to the center L-IPSC, compared between dim- and light-adapted conditions at each stimulus distance. The proportion of inhibition was significantly smaller under light adaptation from 100 to 600 μm away from the cell with little inhibition remaining after 200 μm. E: the average proportion of center L-IPSC response that is transient or sustained in dim and light intensity step-controlled conditions (n = 4). L-IPSCs became significantly more transient with light adaptation. F: spatial inhibition curves of peak amplitude in both light conditions. The peak amplitude distribution was significantly narrower and smaller with light adaptation. G: L-IPSC peak amplitude compared between dim- and light-adapted conditions at each stimulus distance. The proportion of inhibition was significantly smaller under light adaptation at 0–500 μm away from the cell with no inhibition present after 300 μm. *P < 0.05; **P < 0.01.