Vibratory stimulation of proximal muscles does not affect cortical components of somatosensory evoked potential following distal nerve stimulation

Objectives: The effects of the proprioceptive activity of the proximal muscles on somatosensory evoked potentials (SEPs) were investigated, using vibratory stimulation of proximal muscle tendons. Methods: SEPs were recorded following electrical median nerve stimulation at the wrist during vibratory stimulation of tendon of pronator teres, biceps and trapezius muscles and fingers in 8 normal subjects. Results: The cortical SEP components, N20, P25 and N33 recorded from the parietal area, and P20 and N30 recorded from frontal area contralateral to the stimulated side, were markedly attenuated by vibratory stimulation applied to the fingers, but unaffected by vibratory stimulation of the proximal muscles. Conclusion: The proprioceptive afferent, especially group Ia muscle spindle afferent, in the relaxed proximal muscles is not likely to contribute to the gating of SEP following distal nerve stimulation.