Fig. 3.

Background-light adaptation of monkey and ground-squirrel cones. (A) Incremental-flash-on-background experiment on a monkey L-cone. (Left) Representative traces (not averages) and (Right) collected data from four monkey L-cones, with normalized flash sensitivity (S_F/S_F^D; see text) plotted against normalized background-light intensity (I_B/I_o; see text) on log-log scales. For each cell, shown by a different symbol, the measurement at each background intensity is the average of multiple trials of the sort shown at Left. The curve is the Weber–Fechner function (see text) with I_o of 9,000 ± 5,300 photons⋅μm⁻²⋅s⁻¹ at 560 nm. (B) Collected data from five ground-squirrel cones, with I_o of 142,000 ± 90,000 photons⋅μm⁻²⋅s⁻¹ at 560 nm. All inner-segment recordings, and all cells gave monophasic flash responses in the absence of background.