1E). In both conditions, subjects equally improved from training to retrieval testing (F1,14 = 13.83 and P = 0.002, for ‘training/retrieval’ main effect). Performance on the digit span test measuring working memory capacity, and the word fluency test measuring the capability for retrieval from long-term memory, also did not differ between conditions (Table 2). Total sleep time was very similar during the tSOS and sham stimulation

conditions (74.1 ± 3.3 vs. 76.2 ± 3.4 min; Table 3), and 4-min intervals of (sham) stimulation also occurred equally often (7.60 ± 0.18 vs. 7.53 ± 0.21 FK506 cell line intervals; Table 3). In most cases (n = 13), subjects were woken after the end of the first REM sleep period. Visual scoring of arousals during the (sham) stimulation periods showed that the number of arousals was, on average, slightly lower during the stimulation condition than during the sham condition (mean ± SEM: 7.27 ± 1.35

vs. 8.93 ± 1.68; P = 0.16), but did not significantly differ between the two conditions. During the 4-min intervals of stimulation, endogenous SWA cannot be separated from the induced tSOS sine wave stimulation signal covering the same frequency band (Fig. 2A). However, after high-pass filtering, an analysis of spindle activity during ongoing stimulation was possible. The corresponding statistical anova included factors representing the stimulation period and the different electrode sites, as well as Tanespimycin an additional phase factor (discriminating up-phases and down-phases of the tSOS sine wave signal). In Pz, induction of SWA by tSOS

was acutely accompanied by distinct increases in a broad frequency range of 8–20 Hz during the anodal up-phases of the oscillating Olopatadine stimulation, as compared with the down-phases of the stimulation signal (F1,14 = 88.45 and P < 0.001 for the 9–15-Hz frequency band; Fig. 2B). This phase-coupling of EEG activity to the tSOS signal covering both the low 9–12-Hz and high 12–15-Hz spindle frequency bands was, for fast spindle activity, most pronounced during the first and third stimulation periods (F5,70 = 3.82 and P = 0.011 for the phase × stimulation period interaction). Exploratory analyses indicated that this phase-coupling also extended to the faster (15–20 Hz) beta frequency band (F1,14 = 72.0 and P < 0.001 for main effect of phase; F5,70 = 2.61 and P = 0.059, for the phase × stimulation period interaction). There was no systematic difference in EEG power in the slow and fast spindle bands or the adjacent beta band (calculated across the entire periods of acute stimulation) from those in the corresponding periods of the sham condition. Analyses of the 1-min stimulation-free intervals immediately following the 4-min intervals of tSOS (vs. sham stimulation) included factors representing the stimulation period and, in the case of the EEG power, the different electrode sites. This analysis revealed a clear tSOS-induced increase in SWS.