Changes in somatosensory evoked responses by repetition of the median nerve stimulation.
OBJECTIVE
We investigate the synaptic factor for the recovery function of evoked responses using a repetitive stimulation technique.


METHODS
Somatosensory evoked cortical magnetic field (SEF) was recorded following stimulation of the median nerve using single to 6-train stimulation in 8 healthy subjects. The SEF responses after each stimulus in the train stimulation were extracted by subtraction of the waveforms.


RESULTS
An attenuation of the SEF components was recognized after the second of the stimuli, but there was no significant attenuation with the third or later stimulations. The root mean square (RMS) of the 1M (peak latency at 20 ms after stimulation) and 4M (70 ms) components were smaller than that of the single stimulation during the train stimulation, while the 2M (30 ms) and 3M (45 ms) components were not attenuated, but the 3M was facilitated at the fourth to sixth stimulation.


CONCLUSIONS
The synaptic factor was not responsible for the attenuation of the SEF components during repetitive stimulation in healthy subjects. The SEF change disclosed a functional difference among the SEF components during the train stimulation, especially among the later components.
Hoshiyama
Minoru
M
Department of Integrative Physiology, National Institute for Physiological Sciences, Myodaiji, Okazaki 444-8585, Japan. hosiyama@nips.ac.jp
Kakigi
Ryusuke
R
D000328:Adult; D004558:Electric Stimulation; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D006801:Humans; D015225:Magnetoencephalography; D008297:Male; D008475:Median Nerve / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology; D013569:Synapses / Q000502:physiology