Effects of cerebellar transcranial direct current stimulation on the cognitive stage of sequence learning.

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Though the cerebellum has been previously implicated in explicit sequence learning, the exact role of this structure in the acquisition of motor skills is not completely clear. The cerebellum contributes to both motor and nonmotor behavior. Thus, this structure not only may contribute to the motoric aspects of sequence learning but may also play a role in the cognitive components of these learning paradigms. Therefore, we investigated the consequence of both disrupting and facilitating cerebellar function using high-definition transcranial direct current stimulation (tDCS) before the completion of an explicit motor sequence learning paradigm. Using a mixed within- and between-subjects design, we employed cathodal (n = 21) and anodal (n = 23) tDCS (relative to sham), targeting the lateral posterior cerebellum, to temporarily modulate function and investigate the resulting effects on the acquisition of a sequential pattern of finger movements. Results indicate that cathodal stimulation has a positive influence on learning while anodal stimulation has the opposite effect, relative to sham. Though the cerebellum is presumed to be primarily involved in motor function and movement coordination, our results support a cognitive contribution that may come into play during the initial stages of learning. Using tDCS targeting the right posterior cerebellum, which communicates with the prefrontal cortex via closed-loop circuits, we found polarity-specific effects of cathodal and anodal stimulation on sequence learning. Thus, our results substantiate the role of the cerebellum in the cognitive aspect of motor learning and provide important new insights into the polarity-specific effects of tDCS in this area.NEW & NOTEWORTHY The cerebellum contributes to motor and cognitive processes. Investigating the cognitive contributions of the cerebellum in explicit sequence learning stands to provide new insights into this learning domain, and cerebellar function more generally. Using high-definition transcranial direct current stimulation, we demonstrated polarity-specific effects of stimulation on explicit sequence learning. We speculate that this is due to facilitation of working memory processes. This provides new evidence supporting a role for the cerebellum in the cognitive aspects of sequence learning.