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Role of intracortical mechanisms in the late part of the silent period to transcranial stimulation of the human motor cortex
Author(s) -
BrasilNeto J.P.,
Cammarota A.,
VallsSolé J.,
PascualLeone A.,
Hallett M.,
Cohen L. G.
Publication year - 1995
Publication title -
acta neurologica scandinavica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.967
H-Index - 95
eISSN - 1600-0404
pISSN - 0001-6314
DOI - 10.1111/j.1600-0404.1995.tb00151.x
Subject(s) - transcranial magnetic stimulation , silent period , motor cortex , neuroscience , excitatory postsynaptic potential , stimulation , inhibitory postsynaptic potential , stimulus (psychology) , brainstem , psychology , evoked potential , cerebral cortex , medicine , psychotherapist
Transcranial magnetic stimulation (TMS) and transcranial electrical stimulation (TES) of the human motor cortex produce a silent period (SP) following motor evoked potentials (MEPs). The early part of the SP can be explained by decreased alpha motor neuron excitability, whereas the late part is presumably due to suprasegmental mechanisms. In order to determine the level of the suprasegmental contribution to the generation of SPs, we recorded excitatory and inhibitory responses to TMS, TES, and percutaneous electrical brainstem stimulation (PBS) in the voluntarily activated first dorsal interosseous muscle of the hand. Stimulus intensities were set so that PBS and TES induced MEPs with areas equal to or larger than those of MEPs obtained with TMS. This procedure revealed that SPs were 49% and 83% shorter with TES and PBS, respectively, than with TMS. As TMS is more effective than TES or PBS in activating cortical interneurons, these findings support the idea that a significant component of the SP arises from intracortical mechanisms.