Concurrent bilateral M1 anodal and right cerebellar cathodal tDCS attenuates learning of a bimanual videogame task

Bimanual movements require complex cortical interactions when learning new motor skills. Previous work has shown that anodal transcranial direct current stimulation (a-tDCS) of one or both primary motor cortices can accelerate learning. Given the cerebellum's role in early motor learning, the present study sought to examine the effect of bilateral primary motor cortex (M1) a-tDCS coupled with cathodal cerebellar tDCS (biM1a + CBc) on learning of a bimanual racing videogame. 40 subjects were enrolled and received either biM1a + CBc (n = 21) or SHAM (n = 19) stimulation for a single practice session. Videogame performance was assessed before and after the practice session, and a follow-up assessment was made 24 h later. Opposite of what was expected, the tDCS stimulation condition resulted in less improvement within a single day of training than the SHAM condition (p = 0.007). Subjects with more gaming experience showed more retention of the training effect between days, regardless of stimulation condition (p = 0.031). These results suggest that the bilateral anodal M1 stimulation paired with cathodal cerebellar stimulation diminishes the rate that online learning occurs for a bimanual racing videogame task. Consistent with many tDCS studies, the electrode montage and current directions are task-specific and cannot be generalized.