Fig. 5.

The rest–activity rhythm of old flies is enhanced when the light–dark cycle (LD) is coupled with a high–low temperature cycle. (A) Old flies have more consolidated daytime activity and less night activity (white arrows), and thus a stronger rest–activity cycle, when the 12 L:12 D cycle is coupled with a 25:21 °C temperature cycle. ‘Y’ denotes young flies (9 days) and ‘O’ denotes old flies (57 days). Raw activity numbers were normalized to the mean of each group and plotted in 30-min bins. (B) Quantification of early night activity under different entrainment conditions. Early night activity was quantified as ratio of activity during the 6 h after lights-off over that of the entire 24 h day and presented as average ± SEM. (C) Raw data from the above experiments were further analyzed for sleep consolidation. LD combined with a temperature cycle (TC) improves sleep consolidation, such that old female and male flies show a larger fraction of long sleep bouts (>150 min). *P < 0.05, **P < 0.01, ***P < 0.001, n.s. (no significant difference) by Student’s t-test. Activity records from the 3rd day of the LD cycle or combined LD and temperature cycle were used for analysis. Individuals that survived < 7 days during the experiment were excluded from the analysis.