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.