Figure 1.

Reduced circadian behavioral rhythm in middle-aged mice. Representative double-plotted actograms of wheel-running activity in C57BL/6J mice showing the effect of aging on circadian rhythms of locomotor activity of young (A) and middle-aged (B) mice. The mice were maintained in LD cycle for 2 weeks and then transferred into DD. Lighting conditions are indicated at the top of the figure; open bars are light phases and closed are dark. C, D, Integrated mean wheel-running activities were plotted along 24 h for the LD condition (C: young, n = 8; D: middle-aged, n = 10).