Fig. 5: Phase-amplitude coupling between slow oscillations and sleep spindles.

a Preferred phase in radians (and mean length of the resultant vector) of slow oscillations at the peak power of sleep spindles, detected at scalp derivation C4, for the IMMO (purple) and CTRL (pink) groups during NREM2 sleep when considering the first 20 min (left) and the whole night (right). Probability density plots of phases (histograms) are also provided. b Top representation of the mean preferred phase and the circular standard deviation of the SO-spindle coupling for the IMMO and CTRL groups on a simulated slow oscillation. Bottom. Peak-locked sleep spindle group average across all concomitant events during the first 20 min of NREM2 sleep, filtered in the sleep spindle frequency band (purple and pink lines), with the bandpass-filtered SO trace (in gray) superimposed to highlight the SO-spindle coupling in both the IMMO (left) and CTRL (right) groups. c Time-frequency maps (in dB) in the 10–20 Hz frequency range of all concomitant events detected at scalp derivation C4 during all NREM2 epochs over the whole night, using epoch windows ranging from −1 to +2.5 s around slow oscillation onset. Time-frequency maps were displayed with the average bandpass-filtered SO trace superimposed to illustrate the high synchronization between sleep spindle power and slow oscillation phase in the IMMO (top) and CTRL (bottom) groups. The stars represent p-values associated with the Watson-William test. **p < 0.01.