We use Welch's method to obtain the power spectrum of the signals recorded with each electrode. The periodogram is calculated for the first four seconds of each signal (4096 points, 1 kHz sampling rate), fragmenting the recordings into 8 segments with 50% overlap and using the Hamming window. The mean dominant frequency (FD) in the scanned area is determined by averaging the maximum peak power spectral density between 5 and 48 Hz at each electrode. The mean spectral concentration (EC) is also calculated by averaging the percentage of the total energy contained in the FrD range ± 0.5 Hz in each recording channel.