Figure 6.

Response at electrode Oz (7-channel EEG) for the different chirp stimulation frequencies for control, interictal and pre-ictal migraine groups, showing an increase of EEG power for the harmonics of the stimulation frequencies between 22–32 Hz during the pre-ictal phase. (a) Overall response power (between 5 and 125 Hz), assessed per stimulation frequency as mean decibel (dB) change from baseline, was not different between groups for the defined EEG bands of interest. (b) Similarly, EEG responses at driving frequencies showed no differences between groups. (c) For the harmonics of the stimulation frequencies, an increased power was present for the pre-ictal group for the high frequency band (27–40 Hz). A one-way ANOVA confirmed group differences across frequency bands (between 22–32 Hz), with post hoc analyses showing an increase in power in the pre-ictal measurement compared to the interictal and control measurements (significance indicated: **p < 0.004 for all frequencies, Bonferroni corrected). Shown per line: mean ± standard error. Note the different y-axis scaling for panels b and c compared to panel a.