To evaluate the effect of multiple sensory stimulation on cortical excitability by using transcranial magnetic stimulation (TMS).

Thirteen right handed young adults without neurological deficit were enrolled. Cortical excitability was tested by measuring recruitment of motor evoked potentials [recruitment curve (RC)], intracortical inhibition (ICI), and intracortical facilitation (ICF) at the abductor pollicis brevis of the dominant hand in two different conditions: (1) group A: active thumb and index finger pinch movement while observing the congruent finger movement in a screen with 0.2 Hz bell sound for 30 minutes, (2) group B: the same active finger movement in a dark screen with the same bell sound for 30 minutes. All of these procedures were done with a randomized crossover design.

The amplitude of MEP and the slope of all RC (140%,160% of the resting motor threshold) of group A showed increment after visually-guided finger movement and the level of ICI showed decrement after visually guided finger movement (p<0.05), but there was no change in the level of ICF (p>0.05) in group A. In group B, the amplitude of MEP and the levels of ICI, ICF showed no significant changes following finger movement with no visual guidance (p>0.05), but the slope of RC with 140% showed increment (p<0.05).

These findings suggest that cortical excitability can be enhanced by simple repetitive motor practice. The congruent sensori-motor stimulations lead to corresponding additional effect on cortical excitability, presumably by recruitment of remote motor neurons.