The Role of the DLPFC in Bilingual and Monolingual Switching: Evidence from MVPA and tDCS
Previous research suggests that the bilingual experience controlling two languages may transfer to non-linguistic control tasks, resulting in a “bilingual advantage.” If this is the case, there should be a neural basis for this transfer (i.e., a region of the brain involved in both types of control). The dorsolateral prefrontal cortex (DLPFC) is one candidate brain region involved in these two types of control. The current studies had two aims. The first was to determine whether bilingual language control and non-linguistic control relate similarly to the DLPFC, and the second was to determine whether bilinguals and monolinguals differed in this relationship. The first study used multi-voxel pattern analysis (MVPA) to determine whether the patterns of fMRI activity in the left and right DLPFC for language control were similar to the patterns of activity for non-linguistic control. In this study, the left DLPFC showed predictable patterns of activity for non-linguistic control in both bilinguals and monolinguals, but no predictable patterns of activity for language control. The second study used transcranial direct current stimulation (tDCS) to directly alter the functioning of the left or right DLPFC for language control and non-linguistic control. In this study, left DLPFC stimulation hurt bilingual performance on the non-linguistic control task, but helped overall performance on the bilingual language control task. These findings suggest that the bilingual DLPFC is involved in language control, but not in a way that benefits non-linguistic control. If a “bilingual advantage” exists, it is important that researchers continue to explore which regions of the brain facilitate the transfer from language control to non-linguistic control.
Bilingualism, Cognitive control, Language control, Multivoxel pattern analysis, Transcranial direct current stimulation, Dorsolateral prefrontal cortex
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