Abstract
We assessed corticospinal excitability during active and, passive movements and motor illusion tasks using transcranial magnetic stimulation (TMS). In active movement tasks, subjects performed rhythmic finger flexion-extension movements. In passive movement tasks, subjects moved their fingers using a servomotor. In motor illusion tasks, subjects observed finger movements of another person reflected in a mirror. We measured the motor evoked potential (MEP) of the first dorsal interosseous muscles of the right hand. Single-pulse TMS was applied to the primary motor cortex, and the amplitude of the MEP was measured on the target muscle after 10 s from the onset of movement. The frequency of the movement was varied between 0.5, 1, 2, 3, and 4 Hz. We found that the MEP amplitude decreased at 2 Hz for all three types of tasks. These results suggest that the proprioception of the index finger or visual feedback decrease corticospinal excitability in optimal rhythmic finger movements.
