Electroencephalography (EEG) results. Upper two curves show the group average of the EEG response in Fpz and Cz channels time locked to the negative peak of spontaneous slow wave. An automatic online algorithm was using the channel Fpz to detect slow waves and the channel Cz was used in group level offline statistics. Below the curves the time points of significant difference between conditions are shown based on paired samples t-test with noncorrected alpha level of 0.01. During the stimulus night the sound stimulus was presented at 600 ms after the slow-wave peak (time zero in this image), whereas during the control night the sound stimulus was missing. Lowest curve shows change in the 14 Hz oscillatory power from baseline (from −2 seconds to zero) in decibels. The grey boxes show the time window (width), mean (horizontal line in the middle), and its standard error (height of the box) of values extracted from the curves for statistical analyses. **p < .01, ***p < .001.