Online polarity-dependent effects of cerebellar transcranial direct current stimulation on motor speed and fine manual dexterity: A randomized controlled trial

OBJECTIVES: To investigate the role of cerebellar transcranial direct current stimulation (ctDCS) in modulating cerebellar functions in the motor domains of fine motor dexterity and motor speed. METHODS: A single-blind, randomized sham-controlled study was conducted between January and July 2018 at the neuroscience laboratory of Imam Abdulrahman Bin Faisal University. A total of 63 healthy participants were assessed for eligibility. Sixty subjects met the criteria of the study and were randomly divided into 3 groups that received anodal, cathodal or sham ctDCS. Subjects performed 2 motor tasks, The Grooved Pegboard test (GPT) assessed fine manual dexterity and the Finger Tapping Task (FTT) assessed motor speed. Subjects undertook the 2 tasks in a single intervention session while 20 minutes of 2mA ctDCS was administered online. The short form of the Edinburgh Handedness Inventory was used to assess handedness and both tasks were performed first with the dominant and then the non-dominant hand. The primary outcome measures included the time of completion of GPT for fine manual dexterity and the mean number of finger-taps for motor speed of each hand. RESULTS: ANOVA revealed a highly significant polarity dependent Group*Task interaction (p<0.01) for FTT scores. ANOVA also revealed a non-significant Group*Task interaction for GPT scores. CONCLUSION: Findings indicate that ctDCS has a modulatory effect on motor speed and could be a promising therapeutic intervention for treatment of neurological conditions with motor deficits.