Bilingualism tunes executive control brain areas
Everyday life requires us to monitor cognitive conflicts induced by distracting information from either perceptual sources (e.g., competing traffic signs when driving) or internal sources (e.g., thoughts about matters irrelevant to the current goal). The anterior cingulate cortex (ACC) is an important component in
the neural circuit mediating cognitive control and one intimately tied to monitoring conflicting information. Language use also requires cognitive control and plausibly recruits a similar circuit. The demand for such control is most evident in bilinguals, and such speakers provide an opportunity to test the generality of the neural mechanisms involved in cognitive control.
In order to directly examine the link between the regions involved in control of language conflict and those involved in cognitive control, more generally, we need to examine the regions involved within the same study. Accordingly, we asked bilinguals to perform a language control task (i.e., language switching) and a nonverbal conflict task (a flanker task) during the same event-related functional magnetic resonance imaging (er-fMRI) session.
The results revealed that the dorsal anterior cingulate cortex (ACC), a structure tightly bound to domain-general executive control functions, is a common locus for language control and resolving nonverbal conflict. We also show an experience-dependent effect in the same region: Bilinguals use this structure more efficiently than monolinguals to monitor nonlinguistic cognitive conflicts. They adapted better to conflicting situations showing less ACC activity while outperforming monolinguals. Importantly, for bilinguals, brain activity in the ACC, as well as behavioral measures, also correlated positively with local gray matter volume. These results suggest that early learning and lifelong practice of 2 languages exert a strong impact upon human neocortical development.
In conclusion, from our combined findings, we suggest that practicing lifelong bilingualism has neurocognitive benefits. The fact that bilinguals learn early in life to resolve language conflicts and to avoid speaking in the nontarget language leads to beneficial plastic changes in the dorsal ACC. Bilinguals not only resolve cognitive conflicts with less neural resource but their brain also adapts better to conflicting situations as shown in our sessions effects analysis of the flanker task. The ACC conflict effect region is more tuned for conflict monitoring in