The EEG was continuously recorded from 28 scalp electrodes mounted on an elastic cap. The electrodes were located at frontal (Fp1, Fp2, FZ, F3, F4, F7, F8), central (CZ, C3, C4), temporal (T3, T4), posterior-temporal (T5, T6), parietal (PZ, P3, P4), and occipital scalp sites (OZ, O1, O2) of the International 10–20 System. Additional electrodes were placed halfway between anterior-temporal and central sites (FTC1, FTC2), central and parietal sites (CP1, CP2), anterior-temporal and parietal sites (TCP1, TCP2), and posterior-temporal and occipital sites (OL, OR). Vertical eye movements were recorded using two electrodes placed below and above the right eye, while horizontal movements were recorded from electrodes placed at the outer canthi of the eyes. Linked ears served as the reference lead. The EEG and the EOG were amplified with a half-amplitude band pass of 0.01–70 Hz. Electrode impedance was kept below 5 kΩ. Continuous EEG and EOG were digitized at a rate of 512 samples per second.
