(A, B) Numbers of episodes (A) and duration (B) of wakefulness (top), NREM sleep (middle), and REM sleep (bottom) every 3 h through a day (left) and during the light (L) and dark (D) periods (right) in young and old mice (n = 5–6). Shading indicates dark period. Values are shown as means ± S.E., #P < 0.05 and ##P < 0.01 by repeated measures ANOVA, *P < 0.05, **P < 0.01, and ***P < 0.001 by repeated measures ANOVA with Bonferroni’s post hoc test (left) or unpaired t test (right). (C) Total amount of wakefulness, NREM sleep, and REM sleep during a 24-h period (24 h total), 12-h light period (12 h light) or 12-h dark period (12 h dark) (n = 5–6). Values are shown as means ± S.E., listed P-values, **P < 0.01 by unpaired t test. (D) EEG spectra of wakefulness (left), NREM sleep (middle), and REM sleep (right) during the light period (n = 5–6). Values are shown as means ± S.E. (E) SWA in the range of frequencies between 0.5 and 4 Hz during NREM sleep for a 24-h period (n = 5–6). Values are shown as means ± S.E. *P < 0.01 by unpaired t test. (F) Schematic of SD. Sleep was deprived for 6 h, between 6 am and 12 pm, followed by a period of RS. (G) Number of sleep attempts during SD from 6 am to 8 am (6–8), 8 am to 9 am (8–9), 9 am to 10 am (9–10), 10 am to 11 am (10–11), and 11 am to 12 pm (11–12) in young and old mice (n = 5–6). Values are shown as means ± S.E., **P < 0.01 and by repeated measures ANOVA with Bonferroni’s post hoc test. (H) SWA after SD in young and old mice (n = 5–6). Each value is relative to the average of the 24-h baseline day. Values are shown as means ± S.E., **P < 0.01 by repeated measures ANOVA with Bonferroni’s post hoc test.