Fig. 1.

Example of the auditory stimulation protocol used by Ngo and colleagues [13], and its effects on the SO rhythm. A. Following detection of a supra-threshold SO down-state (−80 μV; grey line), two 50 ms pulses of pink noise (clicks) are delivered in phase with the two subsequent SO up-states (red lines). The first click occurs during the predicted SO up-state, based on the average delay between the SO negative and positive peak (~0.5 s; obtained for each participant during a prior adaptation night), and the second after a 1.075 s interval corresponding to the typical duration of a full SO cycle. In the sham condition, corresponding time points of would-be stimulation events are marked but no clicks are delivered. The detection routine is paused for 2.5 s after the second click. B. Relative to the sham condition, stimulation typically enhances the SO rhythm, evoking a ‘train’ of three SOs