For functional connectivity analysis, we applied a voxel-wise approach, using the electrode sites to define regions of interest (ROI). To create the ROIs, eLORETA determined the MNI coordinates for the cortical voxels underlying the 19 electrodes of the 10–20 system [55]. The ROIs are centered at the given voxel coordinates (ROI centroid), and include all cortical gray matter voxels within 15 mm distance from the center [24], [55]. The 19 cortical ROIs determined by eLORETA are shown in Table 2. A recently developed index of physiological connectivity, namely lagged phase synchronization was used as measure of functional connectivity between all pairs of ROIs [23], [24], [55], [56]. Lagged phase synchronization measures the similarity (a corrected phase synchrony value) between signals in the frequency domain based on normalized (unit module) Fourier transforms; thus it is related to nonlinear functional connectivity. This lagged connectivity measure is thought to be accurately corrected as it represents the connectivity between two signals after the instantaneous zero-lag contribution (artifactual component) has been excluded. Such a correction is necessary when using scalp EEG signals or estimated intracranial
