The coincidence between late non-phase-locked gamma synchronization response and saccadic eye movements.

The event-related response in the gamma (30-45 Hz) frequency band was studied in healthy subjects (n=45) viewing sequentially presented pictures from the International Affective Picture System. The distinct non-phase-locked gamma response was obtained in characteristic time window (200-400 ms) with clear-cut centro-parietal location. The strong coincidence between induced gamma oscillations and saccadic eye movements was revealed. We suggest that saccade-related gamma increase is another manifestation of the phenomenon known as presaccadic spike potential, which is commonly registered over parietal scalp leads at 10-20 ms prior to saccade onset. It is hypothesized that late non-phase-locked gamma synchronization mainly reflects activity of a system responsible for attentional tuning and motor planning/execution of saccadic eye movements.