Mechanisms underlying functional changes in the primary motor cortex ipsilateral to an active hand

Monica Perez, Leonardo G. Cohen

Research output: Contribution to journalArticle

180 Citations (Scopus)

Abstract

Performance of a unimanual hand motor task results in functional changes in both primary motor cortices (M1ipsilateral and M1 contralateral). The neuronal mechanisms controlling the corticospinal output originated in M1ipsilateral and the resting hand during a unimanual task remain unclear. Here, we assessed functional changes within M1ipsilateral and in interhemispheric inhibition (IHI) associated with parametric increases in unimanual force. We measured motor-evoked potential (MEP) recruitment curves (RCs) and short-interval intracortical inhibition (SICI) in M1ipsilateral, IHI from M1contralateral to M1ipsilateral, and the influence of IHI over SICI using transcranial magnetic stimulation at rest and during 10, 30, and 70% of maximal right wrist flexion force. EMG from the left resting flexor carpi radialis (FCR) muscle was comparable across conditions. Left FCR MEP RCs increased, and SICI decreased with increasing right wrist force. Activity-dependent (rest and 10, 30, and 70%) left FCR maximal MEP size correlated with absolute changes in SICI. IHI decreased with increasing force at matched conditioned MEP amplitudes. IHI and SICI were inversely correlated at increasing forces. In the presence of IHI, SICI decreased at rest and 70% force. In summary, we found activity-dependent changes in (1) SICI in M1ipsilateral, (2) IHI from M1 contralateral to M1ipsilateral, and (3) the influence of IHI over SICI in the left resting hand during force generation by the right hand. Our findings indicate that interactions between GABAergic intracortical circuits mediating SICI and interhemispheric glutamatergic projections between M1s contribute to control activity-dependent changes in corticospinal output to a resting hand during force generation by the opposite hand.

Original languageEnglish (US)
Pages (from-to)5631-5640
Number of pages10
JournalJournal of Neuroscience
Volume28
Issue number22
DOIs
StatePublished - May 28 2008
Externally publishedYes

Fingerprint

Motor Cortex
Motor Evoked Potentials
Hand
Wrist
Transcranial Magnetic Stimulation
Muscles

Keywords

  • Force
  • Interhemispheric inhibition
  • Intracortical inhibition
  • Primary motor cortex
  • Transcallosal pathways
  • Transcranial magnetic stimulation

ASJC Scopus subject areas

  • Neuroscience(all)
  • Medicine(all)

Cite this

Mechanisms underlying functional changes in the primary motor cortex ipsilateral to an active hand. / Perez, Monica; Cohen, Leonardo G.

In: Journal of Neuroscience, Vol. 28, No. 22, 28.05.2008, p. 5631-5640.

Research output: Contribution to journalArticle

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abstract = "Performance of a unimanual hand motor task results in functional changes in both primary motor cortices (M1ipsilateral and M1 contralateral). The neuronal mechanisms controlling the corticospinal output originated in M1ipsilateral and the resting hand during a unimanual task remain unclear. Here, we assessed functional changes within M1ipsilateral and in interhemispheric inhibition (IHI) associated with parametric increases in unimanual force. We measured motor-evoked potential (MEP) recruitment curves (RCs) and short-interval intracortical inhibition (SICI) in M1ipsilateral, IHI from M1contralateral to M1ipsilateral, and the influence of IHI over SICI using transcranial magnetic stimulation at rest and during 10, 30, and 70{\%} of maximal right wrist flexion force. EMG from the left resting flexor carpi radialis (FCR) muscle was comparable across conditions. Left FCR MEP RCs increased, and SICI decreased with increasing right wrist force. Activity-dependent (rest and 10, 30, and 70{\%}) left FCR maximal MEP size correlated with absolute changes in SICI. IHI decreased with increasing force at matched conditioned MEP amplitudes. IHI and SICI were inversely correlated at increasing forces. In the presence of IHI, SICI decreased at rest and 70{\%} force. In summary, we found activity-dependent changes in (1) SICI in M1ipsilateral, (2) IHI from M1 contralateral to M1ipsilateral, and (3) the influence of IHI over SICI in the left resting hand during force generation by the right hand. Our findings indicate that interactions between GABAergic intracortical circuits mediating SICI and interhemispheric glutamatergic projections between M1s contribute to control activity-dependent changes in corticospinal output to a resting hand during force generation by the opposite hand.",
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