Are ipsilateral motor evoked potentials subject to intracortical inhibition?

McCambridge, AB; Stinear, JW; Byblow, WD

Are ipsilateral motor evoked potentials subject to intracortical inhibition?

McCambridge, AB

Stinear, JW Byblow, WD

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Publication Type:: Journal Article
Citation:: Journal of Neurophysiology, 2016, 115 (3), pp. 1735 - 1739
Issue Date:: 2016-03-01

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Field	Value	Language
dc.contributor.author	McCambridge, AB https://orcid.org/0000-0001-6822-4199	en_US
dc.contributor.author	Stinear, JW	en_US
dc.contributor.author	Byblow, WD	en_US
dc.date.available	2016-01-13	en_US
dc.date.issued	2016-03-01	en_US
dc.identifier.citation	Journal of Neurophysiology, 2016, 115 (3), pp. 1735 - 1739	en_US
dc.identifier.issn	0022-3077	en_US
dc.identifier.uri	http://hdl.handle.net/10453/97246
dc.description.abstract	© 2016 the American Physiological Society. Paired-pulse transcranial magnetic stimulation (TMS) can be used to examine intracortical inhibition in primary motor cortex (M1), termed short-interval intracortical inhibition (SICI). To our knowledge, SICI has only been demonstrated in contralateral motor evoked potentials (MEPs). Ipsilateral MEPs (iMEPs) are assumed to reflect excitability of an uncrossed oligosynaptic pathway, and can sometimes be evoked in proximal upper-limb muscles using high-intensity TMS. We examined whether iMEPs in the biceps brachii (BB) would be suppressed by subthreshold conditioning, therefore demonstrating SICI of iMEPs. TMS was delivered to the dominant M1 to evoke conditioned (C) and nonconditioned (NC) iMEPs in the nondominant BB of healthy participants during weak bilateral elbow flexion. The conditioning stimulus intensities tested were 85%, 100%, and 115% of active motor threshold (AMT), at 2 ms and 4 ms interstimulus intervals (ISI). The iMEP ratio (C/NC) was calculated for each condition to assess the amount of inhibition. Inhibition of iMEPs was present at 2 ms ISI with 100% and 115% AMT (both P < 0.03), mediated by a reduction in persistence and size (all P < 0.05). To our knowledge, this is the first demonstration of SICI of iMEPs. This technique may be useful as a tool to better understand the role of ipsilateral M1 during functional motor tasks.	en_US
dc.relation.ispartof	Journal of Neurophysiology	en_US
dc.relation.isbasedon	10.1152/jn.01139.2015	en_US
dc.subject.classification	Neurology & Neurosurgery	en_US
dc.subject.mesh	Elbow	en_US
dc.subject.mesh	Cerebral Cortex	en_US
dc.subject.mesh	Humans	en_US
dc.subject.mesh	Conditioning, Classical	en_US
dc.subject.mesh	Evoked Potentials, Motor	en_US
dc.subject.mesh	Movement	en_US
dc.subject.mesh	Neural Inhibition	en_US
dc.subject.mesh	Adult	en_US
dc.subject.mesh	Female	en_US
dc.subject.mesh	Male	en_US
dc.subject.mesh	Transcranial Magnetic Stimulation	en_US
dc.title	Are ipsilateral motor evoked potentials subject to intracortical inhibition?	en_US
dc.type	Journal Article
utslib.citation.volume	3	en_US
utslib.citation.volume	115	en_US
utslib.for	1116 Medical Physiology	en_US
utslib.for	11 Medical and Health Sciences	en_US
utslib.for	17 Psychology and Cognitive Sciences	en_US
pubs.embargo.period	Not known	en_US
pubs.organisational-group	/University of Technology Sydney
pubs.organisational-group	/University of Technology Sydney/Graduate School of Health
utslib.copyright.status	closed_access
pubs.issue	3	en_US
pubs.publication-status	Published	en_US
pubs.volume	115	en_US

Abstract:

© 2016 the American Physiological Society. Paired-pulse transcranial magnetic stimulation (TMS) can be used to examine intracortical inhibition in primary motor cortex (M1), termed short-interval intracortical inhibition (SICI). To our knowledge, SICI has only been demonstrated in contralateral motor evoked potentials (MEPs). Ipsilateral MEPs (iMEPs) are assumed to reflect excitability of an uncrossed oligosynaptic pathway, and can sometimes be evoked in proximal upper-limb muscles using high-intensity TMS. We examined whether iMEPs in the biceps brachii (BB) would be suppressed by subthreshold conditioning, therefore demonstrating SICI of iMEPs. TMS was delivered to the dominant M1 to evoke conditioned (C) and nonconditioned (NC) iMEPs in the nondominant BB of healthy participants during weak bilateral elbow flexion. The conditioning stimulus intensities tested were 85%, 100%, and 115% of active motor threshold (AMT), at 2 ms and 4 ms interstimulus intervals (ISI). The iMEP ratio (C/NC) was calculated for each condition to assess the amount of inhibition. Inhibition of iMEPs was present at 2 ms ISI with 100% and 115% AMT (both P < 0.03), mediated by a reduction in persistence and size (all P < 0.05). To our knowledge, this is the first demonstration of SICI of iMEPs. This technique may be useful as a tool to better understand the role of ipsilateral M1 during functional motor tasks.

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http://hdl.handle.net/10453/97246