P1-5-09. The effect of weight load added to thumb on short-latency somatosensory evoked potentials

Abstract

This study examined the effects of unilateral and bilateral holding tasks with weight loads added to the thumbs on short-latency somatosensory evoked potentials (SSEP). Nine healthy volunteers participated in this study. The participants assumed a supine position with the forearms supinated. During palmar adduction, a 250 g weight was loaded onto the phalanx of the thumb. The holding tasks consisted of maintaining the joint angle of the thumb of the right hand, left hand, or bilateral hands. SSEP following right median nerve stimulation was recorded, and the amplitudes of N9, N13, N20, and N20-P25 components were analyzed. The amplitudes of N9 and N13 did not change during any tasks, whereas the amplitudes of N20 and N20-P25 were significantly lower in the task with right hand loaded. It is thought that the excitability of the motor-related area that activated with voluntary movement suppressed sensory input to the somatosensory area. These results suggest that the high excitability of the left motorrelated area that occurred with right hand movement suppressed the sensory input to the somatosensory area more than when bilateral hands were used.