Polarity-dependent cerebellar transcranial direct current stimulation modulates online functions of the alerting attention network.

OBJECTIVES: To investigate the modulatory effect of anodal, cathodal and sham cerebellar transcranial direct current stimulation (ctDCS) on the efficiency of the 3 attention networks namely alerting network, orienting network, and the network of executive control. METHODS: A sham-controlled, single-blind study. Experiments were performed at the neuroscience lab of Imam Abdulrahman Bin Faisal University, Dammam, Kingdom of Saudi Arabia, between the months of January-July of 2018. Sixty-three healthy subjects were assessed for eligibility and a total of 60 subjects (30 males and 30 females) met the inclusion criteria. Subjects were randomly divided into 3 groups that received a single 20-minute session of 2 mA of anodal, cathodal or sham ctDCS while performing tasks. The tasks corresponded to the 3 attention networks-vigilance task assessed the alerting network, Posner's attention task assessed the orienting network and Flanker task assessed the network of executive control. The Edinburgh handedness inventory-short form determined the subjects' handedness. RESULTS: Analysis of variance (ANOVA) showed a highly significant polarity-independent group*task effect (p=0.003) for the vigilance task. Moreover, there was a significant polarity-independent group*task effect for valid cues (p=0.006). A polarity-dependent group*task effect was observed for invalid cues (p=0.011). CONCLUSION: Conclusion: Findings demonstrate that ctDCS modulates alerting attention and highlights a more profound effect of cerebellar modulation in attention tasks with higher cognitive load.

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 less than 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.