tDCS of the Cerebellum: Effects on Language Articulation and Verbal Fluency

Evidence from neuroimaging and cerebellar lesion studies indicate that the cerebellum plays a role in language articulation and verbal fluency. Previous studies have established that distinct areas of the cerebellum are differentially active during each of these tasks, with articulation engaging the anterior cerebellum and verbal fluency activating areas of the right posterolateral cerebellum. This study examined the effects of neuromodulation of the cerebellum on language articulation and semantic and phonemic verbal fluency. We used anodal transcranial direct current stimulation (tDCS) to apply 2 mA of current to two sites in the right cerebellum: the "motor" site (3 cm lateral to the inion) and the "cognitive" site (4 cm lateral to the inion and 1 cm down). Participants (17 females, 14 males; mean age 23.4 ± 6.3 years) completed articulation and fluency measures pre- and post- 20 min of motor (n=11), cognitive (n=10), or sham (n=10) tDCS. Subjects receiving tDCS to the motor site produced fewer syllables of "ba" in a 30 s period than the cognitive and sham tDCS groups. Subjects in the sham and motor groups showed a practice effect after tDCS on a semantic fluency task; however, tDCS over the cognitive site seemed to block this practice effect. Performance on the phonemic fluency task was not affected by anodal tDCS. The findings from this study support the idea that the cerebellum is involved in both motor and cognitive aspects of language, and that different regions of the cerebellum mediate performance on articulation and fluency tasks.