Abstract
Bilingualism is a worldwide phenomenon and provides an opportunity to understand how the brain represents language processing. Although many studies have investigated the neural mechanism of bilingualism, it still remain unclear how brain systems are involved in the second language processing. Here, we examined the neural dynamics of bilinguals with medium proficiency during auditory word processing. Korean–English (K–E) bilinguals were recruited for the study (L1: Korean and L2: English). They performed a word comprehension task on phonological and semantic aspects by hearing words. We compared their task performance, task-induced regional activity, and functional connectivity (FC) between L1 and L2 processing. Brain activation analyses revealed that L2 evoked more widespread and stronger activation in brain regions involved in auditory word processing and the increased regional activity in L2 was prominent during phonological processing. Moreover, L2 evoked up-regulation during semantic processing was associated with L2 proficiency. FC analyses demonstrated that the intra-network connectivity showed stronger in the language network (LN), dorsal attention network (DAN), and default mode network (DMN) in L2 than L1. For the L2 phonological processing, the increased FC within the DAN was positively correlated with individuals’ L2 proficiency. Also, L2 semantic processing induced the enhanced internetwork connectivity between the LN and DMN. Our findings suggest that L2 processing in K–E bilinguals induces dynamic changes in the brain at a regional and network-level and FC analysis can disentangle the different networks involvement in L2 auditory word processing according to two key features: phonology and semantics.
Highlights
Bilingualism is a worldwide phenomenon and more than half of the world’s population is estimated as bilinguals (Grosjean, 2010)
In the contrast of phonological judgment task (PT) > semantic judgment task (ST), we found a significant activation in the bilateral supramarginal gyrus (SMG), inferior parietal lobe/inferior parietal sulcus (IPL/IPS), right precentral gyrus and right SFG only for L2 (Figure 3C), whereas, in the ST > PT contrast, there was a significant activation in the left inferior frontal gyrus (IFG) and superior frontal gyrus (SFG) for both languages (Figure 3D)
We found that the increased functional connectivity (FC) in the dorsal attention network (DAN) during the L2 PT was significantly correlated with the Test of English for International Communication (TOEIC) score (Figure 6D)
Summary
Bilingualism is a worldwide phenomenon and more than half of the world’s population is estimated as bilinguals (Grosjean, 2010). Functional neuroimaging studies have investigated the neural correlates of languages in bilinguals (for the review, see Abutalebi et al, 2001; Kroll and Groot, 2005; Stowe, 2005; Indefrey, 2006; Abutalebi, 2008; Sebastian et al, 2011). We investigated the neural mechanism of Korean–English bilinguals during auditory word compression by controlling these factors
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