Skip to main content
. 2012 Apr 30;590(Pt 13):3035–3045. doi: 10.1113/jphysiol.2012.227892

Figure 2. Individual plasma melatonin profiles before and after bright or dim background light exposure.

Figure 2

Individual plasma melatonin profiles are shown for four participants corresponding to Fig. 1 during constant routine (CR) 1 (•) and CR2 (◦) following exposure to a 1 h bright white light pulse (top panels) or the corresponding <3 lux dim background light condition (bottom panels). The timing of the bright white or <3 lux dim background light exposure on the day before CR2 is marked by an open box. In panel A, the 1 h bright white light exposure caused a −1.44 h phase delay shift (Δϕ) of the circadian pacemaker when timed to occur in the late subjective night compared to an advance of +0.17 h in the <3 lux dim background light condition (panel B). In panel C, bright white light exposure in the early subjective morning caused a +0.99 h phase advance compared to +0.61 h in the <3 lux dim background light (panel D). Dim light melatonin onset (DLMO) level is indicated for each participant by a dotted line.