Inter-hemispheric asymmetry of ipsilateral corticofugal projections to proximal muscles in humans

Colum D. MacKinnon, Angelo Quartarone, John C. Rothwell

Research output: Contribution to journalArticle

20 Citations (Scopus)

Abstract

Motor evoked potentials (MEPs) elicited in many proximal or truncal muscles by ipsilateral transcranial magnetic stimulation (TMS) are thought to be mediated by an oligosynaptic corticofugal pathway and not by uncrossed corticospinal collaterals. In the present study, we compared the input-output properties and scalp surface topography of the ipsilateral and contralateral projections to pectoralis major (PM) and latissimus dorsi (LD) in seven healthy subjects. In six subjects, ipsilateral MEPs evoked by stimulation of one hemisphere (dominant ipsilateral hemisphere) were markedly larger in amplitude than the MEPs evoked in the opposite hemisphere (non-dominant ipsilateral hemisphere). The dominant ipsilateral hemisphere MEPs were significantly larger than the non-dominant MEPs (p<0.02) by an average factor of 3.6 and 3.4 times in PM and LD, respectively. Similarly, there was significant asymmetry between hemispheres in the scalp surface area from which ipsilateral MEPs could be evoked. In contrast, contralateral projections were symmetric in both MEP amplitude and area. Neither the right nor left hemisphere was consistently the dominant ipsilateral hemisphere. The ipsilateral centre of gravity (CoG) for PM was located an average of 0.8±0.6 cm posterior to the contralateral CoG, but no significant differences were observed between ipsilateral and contralateral CoGs in LD. These results demonstrate that the excitability of ipsilateral corticofugal projections to PM and LD are asymmetric between hemispheres.

Original languageEnglish (US)
Pages (from-to)225-233
Number of pages9
JournalExperimental Brain Research
Volume157
Issue number2
DOIs
StatePublished - Jan 1 2004

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Motor Evoked Potentials
Superficial Back Muscles
Muscles
Gravitation
Scalp
Surface Properties
Transcranial Magnetic Stimulation
Healthy Volunteers

Keywords

  • Ipsilateral projections
  • Motor cortex
  • Proximal muscles
  • Transcranial magnetic stimulation

Cite this

Inter-hemispheric asymmetry of ipsilateral corticofugal projections to proximal muscles in humans. / MacKinnon, Colum D.; Quartarone, Angelo; Rothwell, John C.

In: Experimental Brain Research, Vol. 157, No. 2, 01.01.2004, p. 225-233.

Research output: Contribution to journalArticle

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