Dynamic Language Network in Early and Late Cantonese-Mandarin Bilinguals.

Xiaojin Liu,Ruiwang Huang,Xiaoxi Chen,Miao Zhong,Meiqi Niu,Zhi Lu,Liu Tu,Ling Zhao

doi:10.3389/fpsyg.2020.01189

Xiaojin Liu, Ruiwang Huang + Show 6 more

Open Access

https://doi.org/10.3389/fpsyg.2020.01189

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Abstract

The brain representation of language in bilinguals is sculptured by several factors, such as age of acquisition (AoA) and proficiency level (PL) in second language. Although the effect of AoA-L2 on brain function and structure has been studied, little attention is devoted to dynamic properties of the language network and their differences between early and late bilinguals. In this study, we acquired resting-state fMRI data from early and late Cantonese (L1)–Mandarin (L2) bilinguals with high PLs of verbal fluency in both languages. We then analyzed dynamic functional connectivity (dFC) by using the sliding-windows approach, estimated the dFC states by using the k-means clustering algorithm, and calculated the dynamic topological properties of the language network for the early and late bilinguals. We detected four dFC states, State 1, State 2, State 3, and State 4, which may be related to phonetic processing, semantic processing, language control, and syntactic processing, respectively. Compared to the late bilinguals, the early bilinguals showed higher dFC between the inferior frontal area and the temporal area in State 1 and State 2, while higher dFC between the cerebellum and other regions in State 3. The early bilinguals showed a higher clustering coefficient and local and global efficiency in State 1 and State 3, but lower characteristic path length in State 1, than the late bilinguals. Together, these results suggested that AoA-L2 affects temporal neural activation and dynamic topological properties of the language network. These findings provide new information to understand the effect of experience of L2 acquisition on language network in bilinguals.

Highlights

Bilingual brains can be shaped by age of acquisition in second language (AoA-L2) and proficiency level in L2 (PL-L2) (Abutalebi, 2008)
We selected the subjects from a pool containing 500 volunteers of Cantonese–Mandarin bilinguals based on their age of acquisition in second language (AoA-L2), the performance of listening and oral proficiency level in L1 (PL-L1) and L2 (PLL2), and the exposure period to L1 and L2
We found four dynamic functional connectivity (dFC) states of the language network in both early and late bilinguals (Figure 3B result was consistent with previous studies (Zalesky et al, 2014; Betzel et al, 2016; Kabbara et al, 2017; Shine and Poldrack, 2018), which suggested that the dynamic organization of the functional network occurred at different time

Summary

Introduction

Bilingual brains can be shaped by age of acquisition in second language (AoA-L2) and proficiency level in L2 (PL-L2) (Abutalebi, 2008). Gullifer et al (2018) selected the anterior cingulate (BA 24), the left caudate, the inferior frontal gyrus (IFG, BA 44, and BA 47), and the inferior parietal lobule (IPL, BA 40) as seeds to study the impact of AoA-L2 on resting-state FC in French– English bilinguals They found that earlier AoA-L2 related to higher FC between left and right IFG, and to reduced reliance on proactive executive control during the completion of an AXContinuous Performance Task outside the MRI scanner. These results suggested that different experiences of L2 acquisition impact brain intrinsic FC patterns and neural network involved in the executive control. The above studies indicated that the AoA-L2 influences brain functional and structural neuroplasticity in bilinguals

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