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. 2020 Aug 19;2:100022. doi: 10.1016/j.sleepx.2020.100022

Fig. 1.

Fig. 1

Exogenous-melatonin-induced shifts and bright-light-induced shifts of the endogenous melatonin rhythm. The endogenous melatonin rhythm is advanced the most when exogenous melatonin is administered 5 h before the dim light melatonin onset (DLMO) (a); when administered 10 h after DLMO it is delayed the most (b). Bright light during the increasing phase of the melatonin curve delays the endogenous melatonin rhythm (c). Bright light during the decreasing phase of the melatonin curve advances the endogenous melatonin rhythm (d). As the natural sleep–wake rhythm is associated with the endogenous melatonin rhythm, exogenous melatonin- and bright light-induced shifts of the endogenous melatonin rhythm parallel sleep–wake rhythm shifts.