Crossed corticospinal facilitation between arm and trunk muscles in humans

Shin Yi Chiou, Paul H. Strutton, Monica A. Perez

Research output: Contribution to journalArticle

Abstract

A voluntary contraction of muscles with one arm increases the excitability of corticospinal projections to the contralateral resting arm, a phenomenon known as crossed facilitation. Although many motor tasks engage simultaneous activation of the arm and trunk, interactions between corticospinal projections targeting these segments remain largely unknown. Using transcranial magnetic stimulation over the trunk representation of the primary motor cortex, we examined motor-evoked potentials (MEPs) in the resting erector spinae (ES) muscle when the contralateral arm remained at rest or performed 20% of isometric maximal voluntary contraction (MVC) into index finger abduction, thumb abduction, elbow flexion, and elbow extension. We found that MEP size in the ES increased during all voluntary contractions, with greater facilitation occurring during elbow flexion and index finger abduction. To further examine the origin of changes in MEP size, we measured short-interval intracortical inhibition (SICI) and cervicomedullary MEPs (CMEPs) in the ES muscle during elbow flexion and index finger abduction and when the arm remained at rest. Notably, SICI decreased and CMEPs remained unchanged in the ES during both voluntary contractions compared with rest, suggesting a cortical origin for the effects. Our findings reveal crossed facilitatory interactions between trunk extensor and proximal and distal arm muscles, particularly for elbow flexor and index finger muscles, likely involving cortical mechanisms. These interactions might reflect the different role of these muscles during functionally relevant arm and trunk movements. NEW & NOTEWORTHY Many of the tasks of daily life involve simultaneous activation of the arm and trunk. We found that responses in the erector spinae muscles evoked by motor cortical stimulation increased in size during elbow flexion and extension and during index finger abduction and thumb abduction. Crossed facilitation with the trunk was more pronounced during elbow flexion and index finger abduction. These results might reflect the different role of these muscles during arm and trunk movements.

Original languageEnglish (US)
Pages (from-to)2595-2602
Number of pages8
JournalJournal of neurophysiology
Volume120
Issue number5
DOIs
StatePublished - Jan 1 2018

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Arm
Elbow
Muscles
Fingers
Motor Evoked Potentials
Thumb
Transcranial Magnetic Stimulation
Motor Cortex
Skeletal Muscle

Keywords

  • Back muscles
  • Corticospinal pathway
  • Erector spinae
  • Intracortical inhibition
  • Motor-evoked potentials
  • Subcortical pathways

ASJC Scopus subject areas

  • Neuroscience(all)
  • Physiology

Cite this

Crossed corticospinal facilitation between arm and trunk muscles in humans. / Chiou, Shin Yi; Strutton, Paul H.; Perez, Monica A.

In: Journal of neurophysiology, Vol. 120, No. 5, 01.01.2018, p. 2595-2602.

Research output: Contribution to journalArticle

Chiou, Shin Yi ; Strutton, Paul H. ; Perez, Monica A. / Crossed corticospinal facilitation between arm and trunk muscles in humans. In: Journal of neurophysiology. 2018 ; Vol. 120, No. 5. pp. 2595-2602.
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