Enhancing Encoding of a Motor Memory in the Primary Motor Cortex By Cortical Stimulation

Motor training results in encoding of motor memories, a form of use-dependent plasticity. Here we tested the hypothesis that transcranial magnetic stimulation (TMS) synchronously applied to a motor cortex engaged in a motor training task could enhance this plastic process. Healthy volunteers were studied in four sessions: training consisting of performance of directionally specific voluntary thumb movements (Train alone), training with TMS delivered during the execution of the training movement in a strictly temporal relationship to the motor cortex contralateral (Train+TMS synchronouscontra) and ipsilateral (Train+TMS synchronousipsi) to the training hand, and training with TMS delivered asynchronous to the training movement to the motor cortex contralateral to the training hand (Train+TMS asynchronouscontra). Train alone, Train+TMS synchronouscontra, and Train+TMS asynchronouscontra but not Train+TMS synchronousipsi elicited a clear motor memory. The longevity of the encoded memory was significantly enh...