Effects of short-term dual action-simulation training combined with transcranial magnetic stimulation on corticospinal excitation and finger motor performance.

Action-simulation training using action observation (AO), motor imagery (MI), or a combination of both (AOMI) may improve motor function in patients with neurological diseases. Although multiple sessions over several days or weeks are necessary to produce neurophysiological and behavioral effects in patients, the aftereffects of a single session are crucial for achieving long-term outcomes. This study aimed to investigate whether a single session of dual action-simulation (AOMI) training combined with transcranial magnetic stimulation (TMS) induces plastic changes in corticospinal excitation over time and affects motor performance in healthy individuals. The results demonstrated that 20 min of AOMI + TMS training produced a sustained increase in the amplitudes of motor-evoked potentials (MEPs), lasting for >30 min. In addition, interindividual variations in MEP amplitudes after AOMI + TMS could be predicted using MEP amplitude changes during training. The control experiments (MI + TMS, AO + TMS, and AOMI + TMS) used to clarify which combination of the training components promoted increased MEP amplitudes, did not induce significant plastic changes. Furthermore, participants who underwent AOMI + TMS showed improved finger motor performance after training, whereas the control participants did not. These findings suggest that a single session of dual action-simulation training combined with TMS enhances corticospinal transmission over time and improves finger motor performance in healthy individuals. This study provides evidence for the effectiveness of a novel action-simulation training protocol, combining action observation (AO) during motor imagery (MI) with transcranial magnetic stimulation (AOMI + TMS). The results showed that a single 20-min session of AOMI + TMS enhanced corticospinal excitation and improved finger-tapping performance in healthy individuals.