For quantitative analysis, we selected the first 60 s of artifact-free data with patients’ eyes open as well as the first 60 s of artifact-free data with patients’ eyes closed. When specific electrode channels still contained artifacts, these channels were removed from the data. Eyes-open and eyes-closed data were analyzed separately. For eyes-open data, only occipital and parietal electrodes (P8, P3, P4, P7, O1, O2) were analyzed to avoid artifacts due to eye movements or blinking. For eyes-closed data, all 21 electrode channels were used (F10, F9, Fp2, Fp1, F8, F4, Fz, F3, F7, T8, C4, Cz, C3, T7, P8, P4, Pz, P3, P7, O2, and O1). For eyes-open and eyes-closed data separately, all EEG electrodes were combined with each other to create all possible bipolar EEG derivations. This resulted in 15 EEG derivations for eyes-open recordings and 210 EEG derivations for eyes-closed recordings. Based on previous literature, the most promising EEG characteristics were determined a priori, and these included the relative power in the δ (0.5-4 Hz), θ (4-8 Hz), α (8-13 Hz), and β (13-30 Hz) frequency bands, the peak frequency, and the slow-fast ratio ([relative δ + relative θ] / [relative α + relative β]).16 These six EEG characteristics were calculated per patient for every EEG derivation for both eyes-open and eyes-closed recordings.