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Type: Journal article
Title: Decreased input to the motor cortex increases motor cortical excitability
Author: Todd, G.
Butler, J.
Gandevia, S.
Taylor, J.
Citation: Clinical Neurophysiology, 2006; 117(11):2496-2503
Publisher: Elsevier Sci Ireland Ltd
Issue Date: 2006
ISSN: 1388-2457
Statement of
Gabrielle Todd, Jane E. Butler, Gandevia, and Janet L. Taylor
Abstract: <h4>Objective</h4>To investigate whether a short-duration reduction of input to the motor cortex affects excitability in the hand region of the motor cortex.<h4>Methods</h4>Subjects (n=10) received sets of transcranial magnetic stimulation of the motor cortex (TMS) and peripheral ulnar nerve stimulation. Stimuli were delivered before and after 20 min of inactivity of the test hand. The evoked compound muscle action potentials were recorded in two relaxed intrinsic hand muscles using surface EMG.<h4>Results</h4>Motor evoked potential size (MEP; expressed relative to the maximal M-wave) increased by approximately 30-40 in both hand muscles (P=0.012) following inactivity. The enlarged MEP was not associated with changes in F-wave size, a marker of motoneurone excitability, or changes in intracortical inhibition and facilitation measured with paired-pulse TMS.<h4>Conclusions</h4>MEP growth most likely reflects an increase in motor cortical excitability. The increased excitability appears to be more associated with reduced voluntary drive to and from the motor cortex rather than reduced afferent input from the periphery.<h4>Significance</h4>These results have important implications for any investigation of motor cortical excitability in relaxed subjects. The outcome of an experimental intervention is the net result of the intervention itself and alterations in cortical excitability produced by the subjects' inactivity.
Keywords: Hand; Motor Cortex; Neural Pathways; Ulnar Nerve; Humans; Electromyography; Electric Stimulation; Sensory Thresholds; Arousal; Skin Temperature; Evoked Potentials; Movement; Adult; Female; Male; Transcranial Magnetic Stimulation
Description: Copyright © 2006 International Federation of Clinical Neurophysiology Published by Elsevier Ireland Ltd.
RMID: 0020061901
DOI: 10.1016/j.clinph.2006.07.303
Appears in Collections:Molecular and Biomedical Science publications

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