Cerebellar tDCS does not modulate language processing performance in healthy individuals

Abstract

Clinical and neuroscientific studies in healthy volunteers have established that the cerebellum contributes to language comprehension and production. Yet most evidence is correlational and the exact role of the cerebellum remains unclear. The aim of this study was to investigate the role of the right cerebellum in unimpaired language comprehension and production using non-invasive brain stimulation. In this double-blind, sham-controlled experiment, thirty-six healthy participants received anodal or sham transcranial direct current (tDCS) stimulation to the right cerebellum while performing a lexical decision, sentence comprehension, verbal fluency and language-unrelated control task. Results showed that anodal relative to sham tDCS caused faster manual responses in the lexical decision task. Additional exploratory analyses suggest load-specific performance modulation in the sentence comprehension and lexical decision task, with tDCS improving performance in low-load trials of the sentence comprehension task and high-load trials in the lexical decision task. Overall, our findings provide evidence for the involvement of the right posterior cerebellum in comprehension-based language tasks requiring a manual response. Further research is needed to dissociate the influence of task difficulty and timing of the underlying cognitive processes.