Modulating Cognition Using Transcranial Direct Current Stimulation of the Cerebellum

Abstract

Numerous studies have emerged recently that demonstrate the possibility of modulating, and in some cases enhancing, cognitive processes by exciting brain regions involved in working memory and attention using transcranial electrical brain stimulation. Some researchers now believe the cerebellum supports cognition, possibly via a remote neuromodulatory effect on the prefrontal cortex. This paper describes a procedure for investigating a role for the cerebellum in cognition using transcranial direct current stimulation (tDCS), and a selection of information-processing tasks of varying task difficulty, which have previously been shown to involve working memory, attention and cerebellar functioning. One task is called the Paced Auditory Serial Addition Task (PASAT) and the other a novel variant of this task called the Paced Auditory Serial Subtraction Task (PASST). A verb generation task and its two controls (noun and verb reading) were also investigated. All five tasks were performed by three separate groups of participants, before and after the modulation of cortico-cerebellar connectivity using anodal, cathodal or sham tDCS over the right cerebellar cortex. The procedure demonstrates how performance (accuracy, verbal response latency and variability) could be selectively improved after cathodal stimulation, but only during tasks that the participants rated as difficult, and not easy. Performance was unchanged by anodal or sham stimulation. These findings demonstrate a role for the cerebellum in cognition, whereby activity in the left prefrontal cortex is likely dis-inhibited by cathodal tDCS over the right cerebellar cortex. Transcranial brain stimulation is growing in popularity in various labs and clinics. However, the after-effects of tDCS are inconsistent between individuals and not always polarity-specific, and may even be task-or loadspecific, all of which requires further study. Future efforts might also be guided towards neuro-enhancement in cerebellar patients presenting with cognitive impairment once a better understanding of brain stimulation mechanisms has emerged.

Task-Specific Facilitation of Cognition by Anodal Transcranial Direct Current Stimulation of the Prefrontal Cortex

“…The sequences used in each task before and after the stimulation period were different, and the numbers in the sequences were in the range of 1–9. Details of each task can be found elsewhere ( Pope 2015 ).…”

The Role of the Pediatric Cerebellum in Motor Functions, Cognition, and Behavior

“…One of the more consistent processes associated with cerebellar activation involves tasks related to working memory or executive function. 31,61-66 Cerebellar activation has also been identified with tasks of attention and timing. 67-70 As with the cerebellar role in language, studies on a cerebellar contribution to cognition largely support a role for the lateral cerebellar hemispheres in supporting cognitive processes.…”

Transcranial direct current stimulation to enhance cognition in euthymic bipolar disorder

“…Other studies investigating the cognitive effects of cerebellar stimulation using tDCS have similarly produced mixed findings. Pope , for example, recently showed that cathodal, but not anodal, tDCS applied to the right cerebellum improved performance on a difficult working memory task. In another study, however, cathodal tDCS similarly given to the right cerebellum reduced practice effects on an auditory attention and working memory task .…”