Figure 4. Responses of SCN neurones to 200 s exposure to light (yellow regions, 100 lux) .

The plots are of firing rate in 1 s bins. A, this cell is strongly activated at the onset of light; the firing rate adapts during continued exposure, and falls promptly when the light is switched off. B, this light‐off cell responds to light with an initial fall in firing rate but then speeds up to exceed the initial firing rate. When the light is switched off, the firing rate increases further before falling again to the initial firing rate. C, this light‐off cell shows a simple adapting inhibition in response to light.