Elsevier

Behavioural Brain Research

Volume 230, Issue 1, 21 April 2012, Pages 144-148
Behavioural Brain Research

Research report
Handedness and the excitability of cortical inhibitory circuits

https://doi.org/10.1016/j.bbr.2012.02.008Get rights and content
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open access

Abstract

Inhibitory processes play a significant role in the control of goal-directed actions. To increase insights into these mechanisms as a function of handedness, we measured the transient inhibition of volitional motor activity induced by single pulse transcranial magnetic stimulation during bimanual isometric contractions with symmetrical and asymmetrical force demands. Here, we assess the cortical silent period (cSP), which associates with intrahemispheric inhibition, and the ipsilateral silent period (iSP), which provides an estimation of interhemispheric inhibition. The data showed that inhibitory processes support the functional regulation of bimanual motor output. Furthermore, right-handers demonstrated asymmetries in intra- and interhemispheric inhibition due to asymmetrical force requirements and hand dominance, whereas left-handers did not show marked differences. In particular, right-handers demonstrated increased inhibitory processing that favoured control of the dominant (left) hemisphere whereas both motor cortices exhibited equal capabilities in left-handers. These observations were specific to the bimanual nature of the task. The present results underline distinct organisational mechanisms of coordinated behaviour in right- and left-handers.

Highlights

► The study assesses inhibitory cortical processes during bimanual tasks. ► Right-handers show inhibitory processing that favours control of the left hemisphere. ► Both primary motor cortices exhibit equal capabilities in left-handers. ► Distinct organisation of coordinated behaviour in right- vs. left-handers.

Keywords

Cortical silent period (cSP)
Ipsilateral silent period (iSP)
Bimanual control

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1

CSR is now at the Department of Bioengineering, University of Strathclyde, Wolfson Building, 106 Rottenrow East, Glasgow, G4 0NW, United Kindom.