Enhanced intraparietal phase-lag synchronization in the high-gamma band during retention of visuospatial working...

Although zero-phase lag between cortical regions has been generally regarded as the optimal state, it has also been suggested that a non-zero phase delay of electroencephalography (EEG) signals in the gamma frequency band between bilateral parietal areas may have a significant meaning. Indeed, the phase delays of the gamma band between the cortical regions are reportedly associated with the direction of communication between the regions. In this study, we aimed to demonstrate synchrony with phase lag between cortical regions involved in visuospatial working memory (VWM) performance. We used EEG to compute the weighted phase lag index (wPLI) from the EEG signals concurrently recorded during the VWM task. An increase in wPLI value between the electrodes positioned over the bilateral parietal areas was observed during the VWM task. The wPLI values positively correlated with the lateralization index (LI) between the left and right visual hemifields. Furthermore, event-related desynchronization of gamma band activity is observed when wPLI peaked. Our findings suggest that phase lagged synchronization of high gamma band over bilateral parietal areas may reflect which information to prioritize during processing of VWM.