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Fig. 4. As a brief demonstration of the circadian rhythm, we left the lights on (A;
male 029) or off (B; male 042) after completing an experiment. Under constant
light or constant dark, EOD repolarization time (
-P2) and amplitude (not
shown) continue to oscillate on a shortened circadian rhythm, though the rise
under free-running conditions is not as steep as occurs immediately after
lights out in laboratory conditions. Vertical dashed lines indicate the
previous times of lights on or off.