Functional Connectivity Reveals Which Language the “Control Regions” Control during Bilingual Production

Abstract

Bilingual studies have revealed critical roles for the dorsal anterior cingulate cortex (dACC) and the left caudate nucleus (Lcaudate) in controlling language processing, but how these regions manage activation of a bilingual’s two languages remains an open question. We addressed this question by identifying the functional connectivity (FC) of these control regions during a picture-naming task by bimodal bilinguals who were fluent in both a spoken and a signed language. To quantify language control processes, we measured the FC of the dACC and Lcaudate with a region specific to each language modality: left superior temporal gyrus (LSTG) for speech and left pre/postcentral gyrus (LPCG) for sign. Picture-naming occurred in either a single- or dual-language context. The results showed that in a single-language context, the dACC exhibited increased FC with the target language region, but not with the non-target language region. During the dual-language context when both languages were alternately the target language, the dACC showed strong FC to the LPCG, the region specific to the less proficient (signed) language. By contrast, the Lcaudate revealed a strong connectivity to the LPCG in the single-language context and to the LSTG (the region specific to spoken language) in the dual-language context. Our findings suggest that the dACC monitors and supports the processing of the target language, and that the Lcaudate controls the selection of the less accessible language. The results support the hypothesis that language control processes adapt to task demands that vary due to different interactional contexts.

Monolingual and bilingual language networks in healthy subjects using functional MRI and graph theory

“…As a minor difference between the groups, we found more frequent activation of secondary language areas in bilinguals. This result aligns with previous studies that demonstrated that the left Caudate and Angular Gyrus are relatively more involved with bilingualism 41 , 42 .…”

Monolingual and bilingual language networks in healthy subjects using functional MRI and graph theory

“…As a minor difference between the groups, we found more frequent activation of secondary language areas in bilinguals. This result aligns with previous studies that show that the left Caudate and Angular Gyrus is relatively more involved with bilingualism [4,5].…”

“…The activation of the DLPFC is deemed maximal when the subject is asked to switch between the known languages [4] and the BG may actively mediate signaling to the prefrontal cortex according to the changing target language being used by the subject at any given time. Specifically, the caudate may regulate the selection of the less accessible language [4,5].…”

“…These differences may impact clinical practice such as pre-surgical planning in evaluating the relevance of each language area. In fact, most of the studies concerning the bilingual language network have aimed to investigate specific areas for bilingualism by employing ad-hoc fMRI tasks [4,5] that have a limited role in the clinical practice.…”

Is Reduced Visual Processing the Price of Language?

“…Bundles connecting modern language processing areas seem to have evolved within the main pathways from the visual areas to the prefrontal cortex; thus, visual stimuli may interfere more with the functioning of areas that are now commonly associated with language processing but also other tasks [ 15 , 16 ]. In addition, involvement through central areas is indicated [ 17 , 18 ].…”