Figure 1.

Forced desynchrony protocol. After a baseline 8-h control night, subjects completed 10 alternating 2:40 sleep and wake intervals, such that sleep opportunities were evenly spaced across the 24-h day. Before the first short sleep and during subsequent short wake periods, subjects ate an isocaloric meal beginning 90 min prior to lights-off. Melatonin onsets are shown for the same subject as in Figure 2 (period = 24.17 h).