Stimulation of the surround suppresses both inhibition and excitation to guinea pig DSGCs. A and B: light-evoked inhibitory (A) and excitatory (B) conductances in a representative guinea pig DSGC in response to narrow (100-μm width, left) and wide (850-μm width, right) bars moving at 400 μm/s in the null (top) and preferred (bottom) directions. Light-evoked conductances are shown for contrasts 20%, 40%, and 80%. C and D: contrast dependence of the integrated inhibitory (C) and excitatory (D) Off (left) and On (right) conductances in response to a narrow (100 μm) and a wide (850 μm) bar moving in the preferred or null direction at 400 μm/s; n = 11. The integrated light-evoked conductances were normalized to the predicted values at 100% contrast, evoked by a narrow bar moving in the null direction, and fit with the Hill equation.