Figure 1. Effects of shifted LD cycles on circadian entrainment and other properties of the rhythm in wheel-running activity.

A, Representative records of wheel-running activity in adult male (top panel) and female (bottom panel) rats that were maintained in a fixed LD 12:12 cycle (left) or exposed to a shifted (12 h/5 d) LD 12:12 cycle (right). Actograms are plotted over a 24-hour 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, Rhythm amplitude, activity duration (α), and total daily wheel-running activity of adult male (top) and female (bottom) rats exposed to fixed or shifted LD cycles. Bars depict average wheel revolutions per 24 hours (±SEM). *, P < .05.