CORTICOSPINAL EXCITABILITY MODULATION DURING MENTAL SIMULATION OF WRIST MOVEMENTS IN HUMAN-SUBJECTS

Motor evoked potentials (MEPs) to magnetic transcranial stimulation (T CS) were simultaneously and bilaterally recorded from flexor carpi rad ialis (FCR) and extensor communis digitorum (ECD) muscles in seven hea lthy and trained subjects. Latencies and amplitudes characteristics of MEPs were investigated under the following randomised conditions: mus cular and mental relaxation; mental simulation, during absolute muscul ar relaxation, selective flexion or extension of the right or left wri st muscles; arithmetical calculation with muscular relaxation. Unspeci fic, diffuse facilitatory effects on MEPs amplitude were induced by me ntal non motor activity (arithmetical calculation), A further specific and lateralised amplitude potentiation on the agonist muscle acting a s 'prime mover' for the mentally simulated movement was consistently f ound in all the subjects, without significant latency changes, Inhibit ory effects on antagonists were evident only in two subjects. (C) 1998 Elsevier Science Ireland Ltd.