Hemisphere Asymmetry during Different Levels of Co-activation of Antagonist Muscles: a Transcranial Magnetic Stimulation Study

Abstract

Contralateral and ipsilateral silent periods were recorded from first dorsal interosseous muscles of the dominant and the non-dominant hand in response to contralateral and ipsilateral transcranial magnetic stimulation (TMS) in twelve right-handed healthy volunteers during isometric index finger abduction and co-activation of antagonist muscles.
 In the dominant hand, contralateral silent period recorded during coactivation of antagonist muscles was significantly shorter than contralateral silent period recorded during isometric index finger abduction. In the nondominant hand, we did not find significant differences.
 In the dominant hand, ipsilateral silent period recorded during co-activation of antagonist muscles was significantly shorter than ipsilateral silent period recorded during isometric index finger abduction. In the non-dominant hand, we did not find significant differences.
 In conclusion, our main finding was the hemisphere asymmetry during co-activation of antagonist muscles. Both, contralateral and ipsilateral silent periods recorded from the dominant right hand were shorter in comparison to those recorded from the non-dominant hand. These findings illustrate the role of co-activation for the better and precise usage of the dominant hand.