In Figs. 3(F)–(H), 4, and 5, four measures, namely, the spectral power, correlation, phase synchrony, and MSC, are analyzed. The solid lines correspond to referential iEEG or scalp EEG, the dashed lines are the corrected iEEG or scalp EEG, the dotted lines correspond to the bipolar iEEG or scalp EEG, and the dashed–dotted lines correspond to the reference signal. In Fig. 5(B), the blue lines correspond to the referential scalp EEG, and the red lines correspond to the corrected scalp EEG. Comparing the spectral power of the referential and corrected iEEGs in Fig. 3(F) and (G), one can see that the iEEG power is reduced in the frequency band 20–70 Hz by the removal of the reference signal. It should be appreciated that physiological brain activity in the alpha band can be seen near 9 Hz for all the referential iEEG, corrected iEEG, bipolar iEEG, and reference signal. Moreover, each referential iEEG has larger power than the corresponding corrected iEEG.
