Figure 1.

Schematic diagram of the 4 night/3 day experimental protocol. Each admission consisted of (Night 1) a habituation night, (Night 2) baseline assessment of circadian temperature and melatonin rhythms, (Night 3) exposure to bright light (1, 2, or 3 hours at 2,000, 4,000, or 8,000 lux) or control (awake in dim light for the same period of time) with a midpoint of 3 h before the core body temperature minimum (CBTmin) measured on the baseline night, and (Night 4) post-exposure measurements of the timing of the nocturnl circadian melatonin rhythm.