Cerebellar transcranial direct current stimulation modulates the fMRI signal in the cerebellar nuclei in a simple motor task

Abstract

BACKGROUND\nIn a seminal paper, Galea et\xa0al. (Modulation of cerebellar excitability by polarity-specific noninvasive direct current stimulation. 2009. J Neurosci 29, 9115-9122) showed that cerebellar transcranial direct current stimulation (ctDCS) alters cerebellar-M1 connectivity. This effect has been explained by ctDCS-related changes of excitability of the cerebellar cortex with consecutive modulation of its main output, the dentate-thalamo-cortical pathway.\n\n\nOBJECTIVES\nThe aim of this functional magnetic resonance imaging (fMRI) study was to provide evidence that cathodal ctDCS decreases the activity of the cerebellar cortex, resulting in increased activity of the cerebellar nuclei, whereas anodal ctDCS has the opposite effect.\n\n\nMETHODS\nA total of 48 participants (female/male: 23/25, age: 23.8\u202f±\u202f4.1yrs., mean\u202f±\u202fstandard deviation) performed a finger tapping task with the right hand in a 3T MRI scanner. Functional MR images were acquired prior, during and after tDCS of the right cerebellum. Participants were assigned randomly to anodal, cathodal or sham ctDCS.\n\n\nRESULTS\nNo significant difference of cerebellar cortical activation was found after comparing the three modes of stimulation. On the level of the dentate nuclei, however, a significant increase of activation was detected during and after cathodal stimulation. Furthermore, dentate nuclei activation was suppressed on a trend level following anodal stimulation.\n\n\nCONCLUSIONS\nThe present findings support the hypothesis that cathodal ctDCS leads to a disinhibition of the dentate nucleus, whereas anodal ctDCS may have the opposite effect.