Event-related coherence as a tool for studying dynamic interaction of brain regions.

This paper demonstrates a simple approach to calculating time courses of coherence for data recorded during an event-related paradigm. Event-related coherence (ERCoh) was investigated between left and right sensorimotor areas, and between contralateral sensorimotor and SMA during discrete right index finger movements. It is demonstrated that ERCoh can provide information regarding the dynamic interaction of spatially separated brain regions. In the upper alpha band, the mu rhythm of the contralateral sensorimotor area is shown to be linearly phase-coupled to rhythmic activity recorded over the SMA. This synchrony between the rhythms decreases during planning and execution of movement when the respective areas become active. In the gamma band, a short-lasting increase in coherence is found between the contralateral sensorimotor area and the SMA prior to movement, indicating possible functional interaction of these areas during the final stages of movement preparation.