Figure 4. Changes in the contrast response functions of an example cell following adaptation to VL₅₀ (A) and VH₅₀ (B).

For both graphs contrast (abscissa) is plotted against spikes per second (ordinate). Open circles represent the non-adapted case while the filled circles represent the adapted case. Continuous lines show the best fit to a sigmoid (see Methods). Dashed horizontal lines represent the spontaneous firing rate. Response gain can be seen as a reduction of the maximum firing rate while contrast gain is a shift in the contrast response function along the log-contrast axis toward higher contrasts.