Analysis of Movement-Related Brain Activities Elicited by External Instructions

Abstract

MEG recording has made it possible to identify activities in the sensorimotor cortex. A few studies have been done about a self-paced voluntary movement [1][2][3], an event-related activity with sensory guidance [4] and the functional organization [5][6]. However, it is still not clear how the temporal feature of each activity in the primary motor cortex is affected by the motivation that starts movement. Because sources of activity in the primary motor and the primary sensory cortex are located on the opposite wall in the central sulcus and are active during movement, the estimation of their activities has been difficult and no one has succeeded to clarify the temporal features of each. We have been studying movement-related brain activities and found that if the movement is triggered by an external Go-stinulus, a steeper change in magnetic fields is observed between the Go-stimulus and the EMG onset [7]. We named this activity as the motor field (MF) refered to the peak of the readiness field at the EMG onset [1]. In this study, we focused on the MF and identified the temporal aspects of the motor activities elicited by different conditions of the movement onset using LED visual stimuli.