Figure 1.

Effects of shifted LD cycles on circadian entrainment and other properties of the rhythm in mouse wheel-running activity. A) Representative daily records of wheel-running activity in mice that were maintained in a fixed LD 12:12 cycle (left) or exposed to a shifted (12 h advance every 5 d) LD 12:12 cycle (right). Actograms are plotted over a 24-h period. The open and closed bars at the top, respectively, signify the timing of the light and dark phase in the fixed and shifted LD 12:12 cycles. B) The period and amplitude of the activity rhythm, and total daily wheel-running activity (revolutions/24 h) of mice exposed to fixed or shifted LD cycles (n = 6). Bars depict mean values (± sem). Asterisks indicate significant differences (P < 0.05) between fixed and shifted LD mice in the period and amplitude of the rhythm in wheel-running activity.