Enhancing Motor Learning through Temporally Specific Transcranial Direct Current Stimulation of the Cerebellum
Motor learning and the application of transcranial direct current stimulation (TDCS) have been the subject of much debate in recent years. The former theory is based on the tight coupling of events, while the latter is applied with low temporal resolution. To address this discrepancy, a recent study aimed to investigate the temporal specificity of TDCS stimulation by applying it in short epochs during a motor adaptation task.
The participants in the study were required to adapt a reaching movement to two opposing velocity-dependent force-fields (clockwise and counter-clockwise), distinguished by a contextual shift in the task display and cursor location. Brief bouts of event-related TDCS (er-TDCS) were applied to either the primary motor cortex (M1) or the cerebellum during movements for one of these learning contexts.
The results of the study showed that when short-duration stimulation was applied to the cerebellum and timed with movement, only the reaching movements performed simultaneously with stimulation were selectively enhanced, while similar movements were left unaffected. The study found no evidence of improved adaptation following M1 er-TDCS, as participants displayed similar levels of error during both stimulated and unstimulated movements.
The study concluded that the coupling of cerebellar stimulation and movement influences timing-dependent mechanisms of plasticity, thereby facilitating enhanced learning in the stimulated context. The results showed that event-related stimulation of the cerebellum selectively improved the adaptation of counter-clockwise trials compared to clockwise trials, while M1 er-TDCS had no effect.
In conclusion, this study highlights the importance of temporal specificity in TDCS stimulation, and suggests that the cerebellum may be a more suitable target for event-related stimulation during motor learning tasks. The results of this study can inform future research and provide a foundation for developing more effective strategies for using TDCS in the study of motor learning.
Reference Paper
Weightman, M. et al. (2022) “Timing is everything: Event-related transcranial direct current stimulation improves motor adaptation,”
Brain Stimulation, 15(3), pp. 750–757.
Available at: https://doi.org/10.1016/j.brs.2022.05.003.