High-Definition tDCS of Noun and Verb Retrieval in Naming and Lexical Decision
High-definition transcranial direct current stimulation (HD-tDCS) is a novel brain stimulation method that has high potential for use in language therapy for speakers with aphasia, due to its safety and focality. This study aimed to obtain foundational data on using HD-tDCS to modulate language processing in healthy speakers. Participants received stimulation either of Broca’s area or of the left angular gyrus (20 min of anodal, cathodal, and sham stimulation on separate days), followed by naming and lexical decision tasks with single-word verb and noun stimuli. We found that cathodal stimulation over both Broca’s area and the left angular gyrus increased naming speed for both verbs and nouns, challenging the traditional view of cathodal stimulation as suppressive or leading to decreased performance. The effect did not extend to the lexical decision task. Additionally, effects of specific stimulation types depended on the order of their administration, suggesting possible physiological carry-over and/or task novelty effects. These results are relevant to the application of HD-tDCS to enhance and direct neural plasticity in patients with neurogenic language disorders.