Extended Data Fig. 2: Ripple and delta features and controls across sleep and sleep deprivation sessions.

(A) Local field potential spectrogram (1–10 Hz) from a sample theta channel during recovery sleep (RS) from three rats with corresponding hypnogram indicating the scored sleep/wake state above (active wake (AW), quiet wake (QW), rapid eye movement (REM) and non-REM (NREM) sleep). The Fourier spectrogram was calculated from the whitened LFP traces using 4 s windows with 1 s overlap. Z-scored delta power (1–4 Hz, smoothed with a 12 s gaussian kernel) is overlaid in white. More detailed sleep scored sessions are available at https://github.com/diba-lab/sleep_loss_hippocampal_replay. (B) The proportion of time spent in each brain state across all sessions. Individual session values overlaid in connected dots (n = 8 NSD session and n = 8 SD sessions). We note that during sleep deprivation from ZT 0-2.5 (SD1) to ZT 2.5-5 (SD2), there was no significant change in the proportion of time in QW (P = 0.958, t(df = 7) = −0.054) or AW (P = 0.769, t(df = 7) = 0.305). (C) The rate of OFF states compared across sessions. For the non-sleep-deprived (NSD) group, OFF states were most prevalent during NS1 (ZT 0-2.5) and decreased over time, in NS2 (ZT 2.5-5) and NS3 (ZT 5-7.5). The rate of OFF states was initially lower in the SD group, but increased from SD1 to SD2, with a further large increase upon RS. (D) The rate of ripple events calculated in 5 min windows decreased over the first 5 h of NSD but remained stable during 5 h of SD. (E) Ripple rate calculated separately for NREM and WAKE states (individual sessions overlaid with connected dots). A decrease in ripple rates is observed in both NREM and WAKE in the NSD group, but there was no change in WAKE ripples from SD1 to SD2 and a decrease from SD2 to RS. Overall, NREM ripple rates were higher in NS1 vs. RS and WAKE ripple rates were higher in SD2 vs. NS2. (F) The ripple probability (solid line = mean, shaded region = s.e.m., n = 8) was modulated by delta waves. (G) However, the modulation depth of ripples by delta ((peak-trough)/mean) was not significantly different across 2.5 h blocks. (H) OFF states were frequently preceded and followed by ripples⁶⁹. Modulation of OFF states by ripples did not change across NSD (n = 103,319 ripples across 8 sessions) but the probability that OFF immediately followed a ripple increased over SD, from SD1 to SD2 and further in RS, with a significant difference between RS and NS1. The inducement of OFF states by ripples is similar to the rise in OFF states following bursts induced by sensory stimulation in the cortex⁷⁶. (I) Interventions needed to stop transitions to sleep during SD were tracked using piezo sensors on the sides of the home cage in 3 sessions. The number of interventions grew with time during SD. (J) Mean and 95% confidence intervals of ripple rate (left) and delta wave rate (right) relative to the onset of interventions. The rate of delta waves and concurrent ripples was higher immediately preceding interventions, consistent with signs of sleepiness that compel such interventions. (K) Ripple features (frequency, sharp wave amplitude and ripple power) evaluated separately in NREM (n = 67007 ripples from 6 NSD sessions, n = 26798 ripples from 7 SD sessions) and WAKE states (n = 74363 ripples from 6 NSD sessions and 128957 ripples from 7 SD sessions). Rightmost panels in each row provide cross-group comparisons in NS1 vs. RS strictly during NREM and NS2 vs. SD2 strictly during WAKE. These results are largely consistent with patterns in Fig. 1g–i, except that here ripple power in NS2 vs. SD2 is not significantly different during WAKE, indicating state-dependence of this effect. Additionally, we note a significant increase in ripple frequency in WAKE from PRE to POST in both NSD and SD groups, indicating an effect of the novel maze exposure. All box plots show the median and top/bottom quartiles (whiskers = 1.5 x interquartile range) of the hierarchically bootstrapped data with individual session means overlaid with connecting dots. Statistics: panels C, E, G, two-sided paired t-tests (within group) and one-sided independent groups (across groups) t-tests; panel D, Pearson correlation coefficients with two-sided p-value; panel H, χ² tests of independence; panel K, two-sided paired within group and one-sided cross-group comparisons with hierarchical bootstrapping; ns (not significant), *P < 0.05, **P < 0.01, ***P < 0.001, with no correction for multiple comparisons. See Supplementary Tables 1 and 2 for additional details.