In the present study, we examined the effect of voluntary movement of one arm on the sensory system of the contralateral arm using somatosensory evoked potential (SEP). Eleven healthy right-handed subjects were enrolled in this study. The subjects were asked to perform tasks of confrontation movements with three fingers of the right hand whose complexity in movement is different at a movement frequency of 1 Hz. In task 1, the confrontation movement of the thumb and the 2nd finger was continued. In task 2, the confrontation movement of the thumb and other fingers was continued (the 2nd, 3rd, 4th, and 5th fingers in that order). In task 3, the confrontation movement of the thumb and the other fingers was continued (2nd, 4th, 3rd, and 5th fingers in that order). No change was observed in any task at the N9 and N13 amplitudes compared with the baseline amplitude. Significant differences were observed in tasks 1 and 3 at the N20 amplitude compared with the baseline amplitude (p<0.01). These results indicate that the voluntary movement of one arm facilitates the primary somatosensory area of the contralateral arm, and that this facilitatory effect is affected by the complexity of the movement.
