Changes in motor cortex excitability following training of a novel goal-directed motor task.

Training of skilled movements leads to typical changes in motor evoked potentials (MEPs). To explore how such changes are related to motor performance and hand preference, a goal-directed movement task was implemented on a haptic interface. Right and left hands of right-handed subjects were trained in two sessions separated by a pause of 10 min. Transcranial magnetic stimulation (TMS) was applied contralaterally to the trained hand before and after each session. Effects of right hand training: after session #1 MEP-facilitation was +60%, intracortical inhibition (ICI) was reduced and task improvement was +37%. Following session #2 all variables remained unchanged. Left hand training: after session #1 MEP-facilitation was +59%, ICI remained unchanged and task improvement was +30%. Following session #2 all variables remained unchanged. It is concluded that mainly the early phase of skill acquisition induces neuroplastic changes. The asymmetry in ICI obviously reflects functional side differences in hand motor control.