Fig. 1

Circadian rhythm characteristics. a A representative double-plotted actogram of wheel-running activity in a C57BL/6J mouse showing entrainment to the LD cycle, free-running under DD, and phase responses to 6-h light pulses. b Phase response curves detailing wheel-running activity rhythms for 6-h light pulses in male mice. The activity onset time was defined as CT; circadian time, 12. The free-running period is set to 24 circadian-hours. c Phase response curves of human sleep rhythms for 3 h of bright light. Open circles by Honma and Honma [16] and closed circles by Minors et al. [17]