Asymmetrical facilitation of motor-evoked potentials following motor practice.

Use-dependent facilitation of motor-evoked potentials evoked by transcranial magnetic stimulation with repetition of simple movements has been well established. Motor-evoked potentials were recorded from two intrinsic hand muscles before and after blocks of motor practice in which study participants made repeated ballistic pinch responses with either their left or their right hand. Despite similar increases in behavioral performance by each hand (measured by the peak acceleration of the force generated by the index finger), practice-related increases in the amplitude of the motor-evoked potentials were greater in the left than in the right motor cortex of right-handed participants. This finding supports the hypothesis that the dominant motor cortex has a greater ability to reorganize with experience than the non-dominant motor cortex.