Concurrent Bilateral M1 and Anodal Cerebellar tDCS Effects on Learning of a Bimanual Video Game Task

The primary motor cortex (M1) and the cerebellum are important sites of processing for motor learning of complex, bimanual tasks. However, little is known about the current and polarity effects of transcranial direct current stimulation (tDCS) when applied concurrently to these sites during learning. Therefore, the present study sought to examine the effect of bilateral primary motor cortex (M1) anodal tDCS coupled with anodal cerebellar tDCS (biM1a + CBa) on learning of a bimanual racing videogame.

Forty-six subjects were enrolled and received either biM1a + CBa (n = 23) or biM1a + CBsham (n = 23) stimulation for a single practice session. Additional data from a previous study in our lab using bilateral primary motor cortex (M1) anodal tDCS coupled with cathodal cerebellar tDCS (biM1a + CBc, n = 21) and a SHAM condition (n = 20) was included in our analysis. Videogame performance was assessed before and after the practice session, and a follow-up assessment took place 24 h later.

Learning and previous gaming experience were negatively correlated, so experience was included as a covariant in the analysis of results. Consistent with the current literature, simultaneous tDCS of both motor cortices, without any cerebellar stimulation, improved learning the most within a single day (p = 0.025). No significant retention effects were observed for any of the conditions (p = 0.87).

These results reinforce the benefits of tDCS to M1 and that, at least in the video game task used in this study, cerebellar stimulation does not add to the learning effect. When using multifocal stimulation montages, careful consideration needs to be given to the relationship between electrode placement, task specificity, previous experience, and individual differences of the participants.