Figure 2

Indications for a K-complex-like response. In all panels, time 0 s corresponds to the onset of isolated stimuli, that is, stimuli with an inter-stimulus interval (ISI) \(\ge\) 5 s. (A) Averaged EEG across stimuli (dotted lines) and auditory evoked response (AER, mean ± 95% CI, thick black line) of channel Fz as in Fig. 1. The bottom panel displays significant differences between conditions (paired t test, FDR corrected). (B) Topography of the difference in N550 amplitude between conditions (STIM\(-\)SHAM). The latency of the N550 component was determined individually for each night, based on the averaged EEG of the channel average in a predefined frontal region of interest (ROI, see Supplementary Fig. S8). White dots represent electrodes with significant differences between conditions (paired t test, cluster corrected, see methods); the black cross indicates the target electrode. (C) Normalized (participant- and frequency-wise, by the trial average of the entire time window) event-related spectral perturbation (ERSP). The ERSP of the channel average in a predefined frontal ROI (see Supplementary Fig. S8) is shown. Contour lines signify significant differences between conditions (paired t test, cluster corrected, see methods). The topography of effect sizes (Hedge’s g) of the mean sigma (900–1500 ms; 12–16 Hz; Hedge’s g value range: 0.46\(-\)1.21) and low slow-wave response (500–1300 ms; 1–1.5 Hz; Hedge’s g value range: 0.93\(-\)2.67) is depicted at the top and bottom, respectively. White dots and black cross can be interpreted as in (B). (D) Low SWA and sigma power (as in (C)), averaged over channels, after isolated (ISI \(\ge\) 5 s; in red) and consecutive stimuli (ISI < 1 s; in gray). Circles represent values of single participants. Stars indicate significant differences (paired t test, *** p < .001). (E) Topography depicting the difference in the number of evoked spindles between conditions (STIM\(-\)SHAM) detected 2 s following isolated stimuli coupling to the positive half-wave (up-phase) of 1 Hz waves (paired t test, cluster corrected, see methods). White dots and black cross can be interpreted as in (B). (F) Topography displaying the difference in the number of up- and down-phase coupled spindles (up\(-\)down), contrasted between conditions (STIM\(-\)SHAM; paired t test, cluster corrected, see methods). White dots and black cross can be interpreted as in (B).