Application of Transcranial Direct Current Stimulation During Motor Skill Acquisition

Abstract

Transcranial direct current stimulation has been used to influence the acquisition of motor skills; however, most studies investigate relatively simple laboratory based motor skills tasks. Since the regions where structural and functional changes support motor learning are dependent on the qualities of the task, translation of the findings to real-world skills has been limited. In general, anodal current stimulation is associated with functional facilitation and cathodal current is associated with functional inhibition. The purpose of this dissertation is to explore the effect of transcranial direct current stimulation of the primary motor cortex and the cerebellum upon the acquisition of novel motor skills that possess varied demands comparable to everyday tasks. In order to study motor skill learning, we investigated 4 unilateral tasks made novel by using the non-dominant hand, ensuring a discernible fast phase of learning in which to observe skill acquisition. In study one, anodal stimulation applied over the primary motor cortex during a 20 minute practice session skill acquisition in a complex dart throwing task compared to cathodal motor cortex stimulation or SHAM. In study two, 20 minutes of anodal motor cortical stimulation while practicing a dexterous tweezer task significantly reduced postpractice pin-placing time compared to SHAM. In study three, anodal motor cortical stimulation during 20 minutes practicing a dexterous rhythmic-timing video game led to significantly higher performance scores compared to SHAM. In study four, in the same videogame task, concurrently stimulating the primary motor cortex with 2 milliamp anodal current while stimulating the cerebellum with 2 milliamp cathodal current during 20 minutes of practice led to significantly higher performance scores compared to SHAM, whereas 2 milliamp anodal primary motor cortex, anodal cerebellar, and cathodal cerebellar stimulation alone was not different than SHAM. These data altogether show that motor cortical transcranial direct current stimulation can facilitate skill acquisition in everyday tasks with a range of gross, fine, and visuomotor demands. They also provide the first evidence of a synergistic effect on motor learning from concurrent primary motor cortex and cerebellar stimulation, which may contribute to the development of novel stimulation protocols.