Fig. 1. Spontaneous activity of Hcrt neurons across sleep/wake states in young and aged mice.

(A and B) Representative EEG, EEG power spectra, EMG, simultaneous Hcrt GCaMP6f signals from (A) young and (B) aged mice. The arrows indicate GCaMP6f transients during sleep (G^S), and the black triangles indicate GCaMP6f epochs associated with wakefulness (G^W). (C) Staged G^S signals during 10 s around the start of G^S transients from identical length (6 hours, 1 hour/mouse) of recorded GCaMP6f signals from young and aged mice (n = 6 mice each group), respectively, during light phase, averaged trace plot (right top), scatter plot of individual G^S duration against G^S peak (young, n = 128; aged, n = 171) (right middle), animal-based comparison of G^S signals for Z score and G^S frequency (right bottom). (D) Staged G^W signals during 10 s around start of G^W epochs from identical length (6 hours, 1 hour/mouse) of recorded GCaMP6f signals from young and aged mice, averaged trace plot (right top), scatter plot of individual G^W duration against G^W peak (young, n = 102; aged, n = 137) (right middle), animal-based comparison of G^W signals for Z score and G^W frequency (right bottom). (E) Animal-based comparison of mean bout duration for sleep, wake, and entire S-W episodes (n = 6 mice each group). (F) Correlation for mean sleep bout duration against G^W bout counts/hour in young, aged, and pooled datasets. Data represent mean ± SEM. In (C) to (E) unpaired t test with Welch’s correction; (F), Spearman correlation, linear fit and 95% confidence band; *P < 0.05, **P < 0.01, ***P < 0.005, ****P < 0.001, †P < 0.0005; statistical details see supplementary text.