Asymmetric facilitation from repeated paired magnetic stimulation of human motor cortex

Repeated stimulation of human motor cortex with pairs of magnetic pulses separated by 1.5 ms has been shown to increase the amplitude of the motor-evoked potentials in activated muscles, indicating a short-term plastic increase of corticospinal excitability. We show here that this increase is greater in the dominant than the nondominant motor cortex of right-handed participants. This finding is a direct demonstration that the potential for plastic synaptic change is greater in the dominant than the nondominant motor cortex and implies that a greater potential for reorganization within the dominant motor cortex is a mechanism of the greater dexterity of the dominant hand.