Modulation of motor learning and memory formation by non-invasive cortical stimulation of the primary motor cortex

Transcranial magnetic (TMS) and direct current (tDCS) stimulation are non-invasive brain stimulation techniques that allow researchers to purposefully modulate cortical excitability in focal areas of the brain. Recent work has provided preclinical evidence indicating that TMS and tDCS can facilitate motor performance, motor memory formation, and motor skill learning in healthy subjects and possibly in patients with brain lesions. Although the optimal stimulation parameters to accomplish these goals remain to be determined, and controlled multicentre clinical studies are lacking, these findings suggest that cortical stimulation techniques could become in the future adjuvant strategies in the rehabilitation of motor deficits. The aim of this article is to critically review these findings and to discuss future directions regarding the possibility of combining these techniques with other interventions in neurorehabilitation.