Figure 2. Mice entrain more rapidly after phase delays than phase advances.

(A) Representative double-plotted actigrams from individually housed C57BL/6J females subjected to 6-hour phase advances (left) and phase delays (right) every 5–6 days. Time (48-hours) is shown on the x-axis and days are ordered sequentially down the y-axis. Each black tick mark indicates the break of an infrared beam within the animal’s cage. Arrows denote days when phase shifts occurred. (B) The number of days (mean ± s.e.m.) required for re-entrainment after a phase shift (for each group, n = 20 (5 animals×4 shifts)). Mice exposed to phase delays achieved entrainment to the new light cycle more rapidly than those exposed to phase advances (** P<0.001, * P<0.005; Student’s t-test).