Fig. 5(A) shows the spectral power for T7, F7, bipolar F7–T7, and the reference signal. One can see that all signals have peaks near 9 Hz except for the bipolar F7–T7, which has a small peak near 7 Hz. The corrected F7 has a small peak at 27.5 Hz which cannot be found in the referential F7 and bipolar F7–T7. In addition, unlike iEEG in Fig. 3(F) and (G), where each referential iEEG has larger power than the corresponding corrected iEEG, the corrected T7 and F7 have larger power than the referential T7 and F7 from 0 to 15 Hz and have smaller power than the referential T7 and F7 from 20 to 30 Hz. Hence, one can conclude the following: 1) The referential and bipolar EEGs cannot correctly reflect brain activity and lead to misinterpretation of EEG, and 2) the reference signal does not always increase power of EEG.
