Motor potentials and the timing of muscular activity

The purpose of this study was to determine whether dominant components of the motor potential recorded from the scalp, were coincident with the rise and fall of muscular activity in single movements and return movements in serial flexion and extension of the elbow. Electroencephalographic recordings obtained from two right-handed subjects through scalp electrodes were averaged by computer and related to EMG, force and displacement of the limb. In the single movements, coincident events in the motor potential indicated the rise and fall of EMG and force. Events in the motor potential of the return movement coincided with the rise of EMG and of force in the first phase, and the rise of EMG in the second phase. Other time relationships were not clear. Relationships between events were clearer in one subject than in the other. This could have been caused by different characteristics in the performance of the task or by problems related to the location of scalp electrodes. The general waveform of the motor potentials and the EMG traces seemed to be related in a few samples of the single movement task, suggesting that other factors than time may also be related between the motor potential and the EMG.