data by the method of Gratton et al. (1983). The EEG was segmented into 2-sec epochs and the epochs with voltage exceeding ± 150 μV were excluded to reduce artifacts. Frequency bands of interest were classified by delta (1–4 Hz), theta (4–8 Hz), alpha (8–12 Hz), beta (12–30 Hz), and gamma (30–50 Hz). Finally, EEG recordings were down-sampled from 1000 to 250 Hz. For each participant, the first 10 artifact-free baseline-corrected epochs (= 5000 samples = 20 s) were selected for further processing.
