Weighted phase lag index (wPLI)

This feature was extracted to calculate functional connectivity in the alpha range. This is a measure of phase-based connectivity calculated in a specific frequency, which accounts only for non-zero phase lag/lead relations between two time series signals⁷³. wPLI is calculated between two neurophysiologic signals and can assume values between 0 and 1. Larger values of wPLI reflect a consistent phase relation between two signals. If the relation between two signals is random, the wPLI value is 0. Connectivity between frontal and parieto-occipital ROIs in the right hemisphere was estimated on the averaged wPLI values calculated over the following electrode clusters: right frontal ROI (F2,FC2,C2,FC4) and right parieto-occipital ROI (PO8,PO4,O2). Similarly, left fronto parieto-occipital connectivity was estimated over left frontal ROI (F1,FC1,C1,FC3) and parieto-occipital ROI (PO7,PO3,O1).