Neuromagnetic oscillatory responses related to the mirror neuron system

Abstract Mu rhythm is the alpha (8–15 Hz) band oscillatory activity recorded over the sensorimotor cortex accompanied by a higher frequency band activity like beta (15–30 Hz) band. The contralateral sensorimotor area shows event-related desynchronization (ERD) of mu rhythm during limb movement and event-related synchronization (ERS) after the termination of the movement. Previous studies reported that ERD/ERS of mu and beta rhythm were detected during movement observation in the absence of physical movement, as well as during movement execution, suggesting that further investigations into the ERD/ERS of mu and beta rhythm in movement observation may elucidate the mechanisms of the mirror neuron system. We examined the post-movement ERS in beta band after movement observation by using MEG and Synthetic Aperture Magnetometry (SAM) analysis. The post-movement beta ERS was estimated over the bilateral, primary, sensorimotor area after the movement execution in all subjects, and estimated over the contralateral, primary, sensorimotor area after movement observation in four out of six subjects. Our results suggest that MEG SAM analysis is useful for the investigation of the mirror neuron system, which can be applied to clinical research for neurological and psychiatric diseases.