Fig. 4: Brain parenchymal resistance is reduced during periods of sleep.

a, Averaged EEG hypnograms from the sleep condition are shown for the overnight period of the Benchmarking Study with WASO excluded in both the hypnograms and sleep R_P (top). Over that period, parenchymal resistance (R_P, bottom) remained constant during the awake state (red) but declined gradually in the sleep state (green). b, Similar trends were observed in the Replication Study. c, During the morning period of the Benchmarking Study, participants underwent a 1.5 h sleep opportunity or period of wakefulness. Left: averaged EEG hypnograms for the overnight and morning periods. Right: during the morning awake period, R_P increased gradually (dashed red), while it declined gradually during the sleep state (dashed green). Parenchymal resistances R_P shown in a, b and c are the average across the participants after normalizing each participant’s R_P measurements by their value at onset of the sleep or wake period. R_P in c for morning wake is plotted starting at the ending value of overnight R_P for illustration purposes. Standard error of the mean is shown for each plot in light grey. The combined overnight and morning Benchmarking Study (c) includes participants whose overnight and morning data passed quality controls.