Fig. 12.

Contrast–response characteristics of CRF excitation and ECI. A, Contrast at half-maximum response for excitation and inhibition. Dashed lines show the upper constraint boundary of the fit. B, The initial contrast gain of excitation and inhibition. The values from fits to average PC and MC responses (Fig. 11) are shown by theopen and filled crosses, respectively. Histograms of each parameter are shown above each plot for CRF excitation and to the right of each plot for extraclassical inhibition.Solid line, PC cells; dashed line, MC cells. The CRF excitation to MC cells is more sensitive to contrast and saturates at lower contrasts than does the excitation to PC cells. The extraclassical inhibition to the two classes shows a similar functional division, but there is more overlap.