Figure 3

SWA and Process S. Time course of slow-wave activity (SWA) in night (A) and morning sleep episodes (B: mornings without SOREMS episodes; C: mornings with SOREMS episodes). NREMS episodes were subdivided into 20 equal intervals and REMS episodes into 5 equal intervals. Mean values per interval were calculated within subjects prior to averaging across subjects (mean ± SEM). For night sleep, only data of recordings with 2 complete cycles were included. Black bars at the top delineate REMS episodes. D: Simulation of homeostatic Process S (solid line) and time course of empirical slow-wave activity (SWA) in consecutive NREMS episodes (filled circles; ± 95 % confidence interval). The level of S at sleep onset of the 4-hour night-time episode was set to 100 %. Based on the average timing of the first NREMS episode and the previously defined time constants [4], the level of Process S at episode midpoint of the first NREMS episode was calculated as 82.7 %. This value equals average SWA of first NREMS episode and served as the reference value for the calculation of relative SWA in the second NREMS episode of the night (61.2 %) and the first NREMS episode of the morning (54.5 %). * S outside the 95% confidence interval of SWA data. Black bars denote sleep episodes.