Facilitatory effect of thinking about movement on motor evoked potentials to transcranial magnetic stimulation of the brain

Surface electromyographic responses were recorded from 9 human abductor pollicis brevis muscles in response to transcranial magnetic stimulation of the brain. Measurements of MEP (motor evoked potential) amplitude were performed with the subject at rest, thinking about a particular movement, and slightly contracting the muscle. It is shown that thinking about the movement has a facilitatory effect on the evoked potentials to magnetic stimulation of the brain, and that the degree of facilitation in thinking is smaller than in voluntary contraction