Sleep during the five 1-min stimulation-free and the 60 min periods following theta-tDCS during NonREM sleep.

Sleep stage scoring for the five 1-minute stimulation-free periods is based on 10-s with mean ± SEM time in the different sleep stages given in seconds. Sleep stage scoring for the 60 minutes following theta-tDCS is based on 30-s epochs with mean ± SEM time in the different sleep stages given as percentage of 30 min. S1–S4, sleep stages 1–4; SWS, Slow wave sleep; REMS, rapid eye movement sleep.

P<0.001;

P<0.01, for pairwise comparisons between the effects of theta-tDCS and sham stimulation.