Research Article

Experimental Brain Research

, Volume 155, Issue 1, pp 19-23

First online:

Transcranial magnetic stimulation reveals asymmetrical efficacy of intracortical circuits in primary motor cortex

  • Geoff HammondAffiliated withSchool of Psychology, The University of Western Australia Email author 
  • , Deb FaulknerAffiliated withSchool of Psychology, The University of Western AustraliaCentre for Neuromuscular and Neurological Disorders, The University of Western Australia
  • , Michelle ByrnesAffiliated withCentre for Neuromuscular and Neurological Disorders, The University of Western Australia
  • , Frank MastagliaAffiliated withCentre for Neuromuscular and Neurological Disorders, The University of Western Australia
  • , Gary ThickbroomAffiliated withCentre for Neuromuscular and Neurological Disorders, The University of Western Australia

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Abstract

The efficacy of inhibitory and excitatory intracortical circuits acting on the representation of an intrinsic hand muscle in the primary motor cortex of both hemispheres was measured with paired transcranial magnetic stimuli in right-handed subjects. Both intracortical inhibition (measured with an interstimulus interval of 3 ms) and intracortical facilitation (measured with an interstimulus interval of 16 ms) developed more rapidly with increasing conditioning stimulus intensity in the dominant than the non-dominant hand. We conclude that the intracortical circuits in the primary motor cortex are more potent in the dominant than the non-dominant hemisphere, and hypothesize that this difference is a factor in the asymmetrical dexterity associated with hand preference.

Keywords

Handedness Motor cortex TMS Intracortical inhibition Intracortical facilitation