Further evidence for excitability changes in human primary motor cortex during ipsilateral voluntary contractions.

Full Abstract

The present study aimed to further investigate whether the intracortical neural circuits within the primary motor cortex (M1) are modulated during ipsilateral voluntary finger movements. Single- and paired-pulse (interstimulus intervals, ISIs; 3 ms and 12 ms) transcranial magnetic stimulations of the left M1 were applied to elicit motor evoked potential (MEP) in the right first dorsal interosseous (Rt-FDI) muscle during voluntary contractions (10% and 30% maximum voluntary contraction) of the left FDI (Lt-FDI) muscle. F-waves of Rt-FDI muscle were recorded under these left index-finger conditions for ensuring that the excitability changes occur at the supraspinal level. MEPs were also recorded during motor imagery of the left index-finger abduction instead of overt movement. The results showed that, in single-pulse transcranial magnetic stimulation (TMS) paradigm, MEPs in Rt-FDI muscle were markedly enhanced during voluntary contractions of Lt-FDI muscle compared with the complete resting state. In paired-pulse TMS paradigm, the short intracortical inhibition was significantly reduced in proportion to increments of the ipsilateral muscle contraction, whereas the intracortical facilitation had no change. F-wave of Rt-FDI muscle was unchanged under these conditions, while MEP in Rt-FDI muscle was also enhanced during motor imagery of the left index-finger abduction. Based on the present results, it is suggested that the intracortical inhibitory neural circuits may be modulated in the transition from rest to activity of the ipsilateral homonymous muscle. The excitability changes in M1 might be induced by overflows of voluntary drive given to the ipsilateral limb, probably via the transcallosal pathway.

Author information

Author/s: Liang, Nan (N); Murakami, Tsuneji (T); Funase, Kozo (K); Narita, Tomohiro (T); Kasai, Tatsuya (T);

Affiliation: Department of Rehabilitation of Locomotor System Dysfunction, Graduate School of Health Sciences, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima, 734-8551, Japan.

Journal and publication information

Publication Type: Journal Article; Research Support, Non-U.S. Gov't

Journal: Neuroscience letters (Neurosci Lett), published in Ireland. (Language: eng)

Reference: 2008-Mar; vol 433 (issue 2) : pp 135-40

Dates: Created 2008/02/29; Completed 2008/06/12;

PMID: 18261851, status: MEDLINE (last retrieved date: 2/18/2009)

Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.

External Links for this article
(including full text providers, if available):

Click Electronic Full-text Provider Links to see options for finding the electronic full text links to this article. Note there may be a subscription or fee required for access to the full text. See our FAQ for information on finding FREE full text articles.

This article may also be located in paper journal collections available in many libraries. Use the Journal and Publication Information above to find the full article.