Prefrontal Transcranial Direct Current Stimulation (tDCS) Has a Domain-Specific Impact on Bilingual Language Control

Researchers debate whether domain-general cognitive control supports bilingual language control through brain regions such as the dorsolateral prefrontal cortex (DLPFC). Transcranial direct current stimulation (tDCS) is a method to alter brain activity, which can lead to causal attribution of task performance to regional brain activity. The current study examined whether the DLPFC enables domain-general control for between-language switching and nonlinguistic switching and whether the control enabled by DLPFC differs between bilinguals and monolinguals. tDCS was applied to the DLPFC of bilingual and monolingual young adults before they performed linguistic and nonlinguistic switching measures. For bilinguals, left DLPFC stimulation selectively worsened nonlinguistic switching, but not within-language switching. Left DLPFC stimulation also resulted in higher overall accuracy on bilingual picture-naming. These findings suggest that language control and cognitive control are distinct processes in relation to the left DLPFC. The left DLPFC may aid bilingual language control, but stimulating it does not benefit nonlinguistic control.