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Facilitation of responses to motor cortex stimulation: Effects of isometric voluntary contraction
Author(s) -
De Noordhout A. Maertens,
Pepin J. L.,
Gerard P.,
Delwaide P. J.
Publication year - 1992
Publication title -
annals of neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.764
H-Index - 296
eISSN - 1531-8249
pISSN - 0364-5134
DOI - 10.1002/ana.410320310
Subject(s) - isometric exercise , facilitation , contraction (grammar) , motor cortex , stimulation , neuroscience , transcranial magnetic stimulation , muscle contraction , electromyography , tibialis anterior muscle , anatomy , medicine , psychology , skeletal muscle
In 7 normal subjects we compared the facilitatory effect of isometric contraction of the tibialis anterior on the size of electromyographic responses evoked in this muscle by electric stimuli applied over the cervical column and by electric and magnetic percutaneous stimulation of the motor cortex. No significant difference was found between the degrees of facilitation of the responses to any of the stimuli. Using collision techniques, we also showed that the pyramidal fibers activated by spinal and cortical stimuli are the same. Facilitation induced by isometric contraction (20% maximum) was of similar or greater magnitude than that found with constant vibration of the tendon of the target muscle. In cases where vibration and contraction had equal facilitatory effects, there was no further facilitation of the responses when both conditions were applied together. These findings indicate that the facilitatory effect of isometric contraction of the target muscle essentially originates at a spinal level rather than in the motor cortex.