Fig. 2.

Results of experimental findings. A) Time-frequency spectrogram from the frontal Fz EEG channel during a representative recording session. The stimulation artifact as a result of both rTMS and tACS at 10 Hz can be seen during stimulation, which is accompanied by harmonic artifacts at 20, 30 and 40 Hz. These artifacts did not affect data quality through the remainder of the recording. B) Changes in 10 Hz EEG power from prefrontal electrodes (AF3-4, F1-6, Fz, FC3-4; see legend) as a function of stimulation protocol and time. Filled circles represent significant pair-wise differences relative to baseline, and asterisks represent significant pair-wise differences relative to sham (p < 0.05, corrected). Error bars indicate the standard error of means. During both, the eyes open (EO) and eyes closed (EC) resting state, 10 Hz power was enhanced relative to baseline and sham stimulation with the peak-synchronized rTMS + tACS protocol, as well as by the same protocol while participants maintained closed eyes during stimulation. Increased power was also observed immediately following stimulation with rTMS alone during EO and tACS alone during EC, which was significantly larger than sham only in the immediate 1-min post stimulation timepoint. C) Grand-average changes in 10 Hz power between pre- and post-stimulation timepoints (1–30 min). Asterisks, according to their color, indicate significant pairwise differences (p < 0.05, corrected). D) Overall, grand-average changes (1–30 min) in prefrontal activity across the power spectrum (1–45 Hz). The red line on 10 Hz indicates the targeted stimulation frequency. Asterisks indicate significant pairwise difference relative to sham (p < 0.05, corrected). (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.)