Promoting use-dependent plasticity with externally-paced training

Objective: To evaluate use-dependent plasticity (UDP) before and after training under metronome-paced and self-paced conditions. Methods: Twelve healthy adults were recruited to this cross-over, pseudo-randomized, repeated measures study. Participants performed wrist extension training that was either self-paced, or externally-paced to an auditory metronome at their preferred movement frequency or at a more demanding frequency. Motor evoked potentials from transcranial magnetic stimulation of left primary motor cortex were recorded in right extensor carpi radialis (ECR) and flexor carpi radialis (FCR) to assess corticomotor excitability. The direction and velocity of TMS-evoked wrist movement (stimulus-evoked velocity, SEV) were measured before and after training to evaluate UDP. Results: The most persistent UDP occurred when training was metronome-paced at the participant's preferred movement frequency. This training protocol produced spatially selective modulation of resting ECR and FCR corticomotor excitability and directional tuning of TMS-evoked wrist movement toward the trained direction. Metronome-paced training at a more demanding frequency resulted in nonspecific facilitation of resting corticomotor excitability, and did not alter TMS-evoked wrist movement. Conclusions: These novel findings indicate that externally-paced training at the individual's preferred frequency facilitates UDP. Significance: UDP underpins motor recovery after stroke. Externally-paced training may be a useful adjunct to movement rehabilitation therapy. (C) 2011 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.