Phase Synchronization and Spectral Coherence Analysis of EEG Activity During Mental Fatigue.

In this article, 2 synchronization measures, phase locking value (PLV) and spectral coherence value (SCV), are used to characterize the changes of the phase synchronization and functional coupling of electroencephalogram (EEG) waves at different brain cortical areas for mental fatigue caused by a long-term cognitive task. The long-term cognitive task induces a significant decrease in the interhemispheric SCVs and PLVs of beta in central and parietal regions, a significant decrease in the intrahemispheric SCVs and PLVs of beta frequency band at the frontal-parietal and central-parietal, and frontal-central middle electrode pairs, suggesting EEG decreases in cooperative processing, strength of functional coupling, and flux of mutual information exchange in the corresponding inter- and intrahemispheres. However, when the mental fatigue level increases, the interhemispheric PLVs of theta are enhanced in the frontal region and C3-Cz electrode pair, and the intrahemispheric PLVs of theta are heightened at frontal-central middle electrode pairs. PLV and SCV measures could reflect the changes of the phase synchronization and functional coupling of EEG waves from time and frequency domains, which are sensitive to mental fatigue. Therefore, PLVs and SCVs can provide an effective and reliable way to quantify brain response to mental fatigue.