Fig. 2. Circadian rhythms parameters examined under standard 12:12 light:dark conditions.

A Actograms of young (left panel) and old (right panel) mice show clear differences in the circadian profiles of activity behaviors between the two age groups. Along the top of the actograms are white and black bars indicating day and night, respectively. Old mice have more diffuse activity during the day, unlike the young mice that are only active at night. B Onset and offsets for these mice were plotted and showed a significant difference in onset, with old animals active more than 30 min before lights off. C The precision of the daily rhythms was also significantly higher in old mice, indicating a less accurate internal clock. Finally, old mice showed dampened rhythms with lower amplitude (D) and mesor (E) values than young mice. *p < 0.05.