Differences in the synchronization of alpha oscillations between anterior and posterior brain regions.

Alpha oscillations generated in the human brain have long been investigated in neuroscience. Synchronized oscillatory activities of numerous neural oscillators are thought to underlie alpha oscillations. The amplitude of alpha oscillations reflects the degree of synchronization, which is often modulated through alpha activation and inactivation, for example, in event-related synchronization and desynchronization. The range of synchronization can be estimated using the similarity between neighboring alpha oscillations. Yet, little is known about how the synchronization range of alpha oscillations varies with alpha activation/inactivation over different brain regions. To examine this, we recorded human electroencephalography (EEG) during different tasks used to modulate alpha oscillations. We found that the synchronization range of posterior alpha oscillations was reduced in the activation phase compared to that in the inactivation phase. In contrast, the synchronization range of anterior alpha oscillations was enhanced in the activation phase compared to that in the inactivation phase. The results imply that the mechanisms generating anterior and posterior alpha oscillations may be different.