Language Brain Representation in Bilinguals With Different Age of Appropriation and Proficiency of the Second Language: A Meta-Analysis of Functional Imaging Studies

Abstract

Language representation in the bilingual brain is the result of many factors, of which age of appropriation (AoA) and proficiency of the second language (L2) are probably the most studied. Many studies indeed compare early and late bilinguals, although it is not yet clear what the role of the so-called critical period in L2 appropriation is. In this study, we carried out coordinate-based meta-analyses to address this issue and to inspect the role of proficiency in addition to that of AoA. After the preliminary inspection of the early (also very early) and late bilinguals’ language networks, we explored the specific activations associated with each language and compared them within and between the groups. Results confirmed that the L2 language brain representation was wider than that associated with L1. This was observed regardless of AoA, although differences were more relevant in the late bilinguals’ group. In particular, L2 entailed a greater enrollment of the brain areas devoted to the executive functions, and this was also observed in proficient bilinguals. The early bilinguals displayed many activation clusters as well, which also included the areas involved in cognitive control. Interestingly, these regions activated even in L1 of both early and late bilingual groups, although less consistently. Overall, these findings suggest that bilinguals in general are constantly subjected to cognitive effort to monitor and regulate the language use, although early AoA and high proficiency are likely to reduce this.

Neural representational similarity between L1 and L2 in spoken and written language processing

“…Furthermore, the conjunction analysis of Chinese > Korean and English > Korean revealed that the left medial frontal gyrus showed greater modality‐similarity for the two L2s than L1. This finding is consistent with a recent meta‐analysis study by Cargnelutti, Tomasino, and Fabbro (2019), which showed that the left medial frontal region (and inferior frontal region) is more consistently activated for L2 than L1, presumably due to the greater attentional and cognitive effort involved in processing L2 than L1. The medial frontal area is an important part of the attention network (e.g., Brown & Braver, 2005; Kearn et al, 2004; Schall, Shtuphorn, & Brown, 2002).…”

Factors Modifying the Amount of Neuroanatomical Overlap between Languages in Bilinguals—A Systematic Review of Neurosurgical Language Mapping Studies

“…Importantly, Sierpowska et al [ 26 , 30 ] found that the middle frontal gyrus mediates the ability to switch between languages. Based on their ESM data and post-operative results, the authors concluded that this region is a hub for a more extended network of areas subserving language switching and cognitive control in bilinguals (see also [ 6 , 43 , 44 ]). The engagement of the middle frontal gyrus in bilingual patients has been demonstrated intraoperatively [ 26 ] but also port-surgically [ 30 ].…”

“…For bilingual patients who continue to require to communicate in both their languages, a major goal of neurosurgery is to map and preserve all their languages [ 2 , 3 ]. There are mixed findings on when and where languages are separate versus overlapping in bilinguals [ 4 , 5 , 6 , 7 , 8 , 9 , 10 ]. Thus, there is an important clinical need for evidence-based principles predicting the likelihood of convergent versus divergent neural representations of the first (L1) and the second language (L2) in neurosurgical patients.…”

Reading across writing systems: A meta-analysis of the neural correlates for first and second language reading

“…Several meta-analyses of bilingual language processing have been performed (Indefrey, 2006; Sebastian, Laird & Kiran, 2011; Liu & Cao, 2016). Brain activities across languages are influenced by language proficiency (Sebastian et al, 2011) and the age of acquisition of the second language (AoA of L2; Liu & Cao, 2016; Cargnelutti, Tomasino & Fabbro, 2019). For highly proficient or early bilinguals, L1 and L2 rely on more similar neural correlates.…”