Abstract
We evaluated the functional relationship between the primary motor cortex and the somatosensory cortex using transcranial magnetic stimulation (TMS) with the assumption that the tactile receptor had been excited by a vibrational stimulus. We measured the subjects' perception thresholds before conducting the TMS experiments. White noise (0-100 Hz) was used as the vibratory stimulation used threshold measurement and was applied to the pulp of the index and little fingers. The TMS experiments comprised three processes. First, we measured the motor evoked potentials (MEPs) by TMS from first dorsal interosseous muscles (FDI) ten times before the stimulation. Second, vibrational stimulation of the double perception threshold value was applied to the pulp of the index finger for 3 min. Third, we measured the MEPs by TMS from FDI ten times again. We compared the MEPs before and after continuous vibrotactile stimulation of the fingertip. The MEPs after stimulation increased. Therefore, we concluded that excitability of the primary motor cortex is changed by somatosensory excitability from continuous vibrotactile stimulation of the fingertip.
