Jung JeYoung, Nam Kichun, Cho Hyesuk, Kim Sunmi
Neuroscience and Aphasia Research Unit, Division of Neuroscience and Experimental Psychology, School of Biological Sciences, The University of Manchester, Manchester, United Kingdom.
Department of Psychology, Korea University, Seoul, South Korea.
Front Psychol. 2018 Jun 18;9:983. doi: 10.3389/fpsyg.2018.00983. eCollection 2018.
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.
双语现象是一种全球现象，为理解大脑如何表征语言处理提供了契机。尽管许多研究已经探究了双语现象的神经机制，但大脑系统如何参与第二语言处理仍不清楚。在此，我们研究了中等水平双语者在听觉单词处理过程中的神经动力学。招募了韩英双语者参与本研究（第一语言：韩语；第二语言：英语）。他们通过听单词在语音和语义方面执行单词理解任务。我们比较了他们在第一语言和第二语言处理之间的任务表现、任务诱发的局部脑区活动以及功能连接（FC）。脑激活分析显示，第二语言在参与听觉单词处理的脑区诱发了更广泛、更强的激活，且在语音处理过程中，第二语言诱发的局部脑区活动增加更为显著。此外，第二语言在语义处理过程中诱发的上调与第二语言水平相关。功能连接分析表明，第二语言在语言网络（LN）、背侧注意网络（DAN）和默认模式网络（DMN）中的网络内连接比第一语言更强。对于第二语言的语音处理，背侧注意网络内功能连接的增加与个体的第二语言水平呈正相关。而且，第二语言语义处理诱发了语言网络和默认模式网络之间网络间连接的增强。我们研究结果表明，韩英双语者的第二语言处理在局部和网络水平上诱发大脑的动态变化，并且功能连接分析可以根据语音和语义这两个关键特征区分不同网络在第二语言听觉单词处理中的参与情况。
