title: Fluency-dependent cortical activation associated with speech production and comprehension in second language learners.
abstract: This functional magnetic resonance imaging (fMRI) study investigated the brain regions underlying language task performance in adult second language (L2) learners. Specifically, we identified brain regions where the level of activation was associated with L2 fluency levels. Thirty Japanese-speaking adults participated in the study. All participants were L2 learners of English and had achieved varying levels of fluency, as determined by a standardized L2 English proficiency test, the Versant English Test (Pearson Education Inc., 2011). When participants performed the oral sentence building task from the production tasks administered, the dorsal part of the left inferior frontal gyrus (dIFG) showed activation patterns that differed depending on the L2 fluency levels: The more fluent the participants were, the more dIFG activation decreased. This decreased activation of the dIFG might reflect the increased automaticity of a syntactic building process. In contrast, when participants performed an oral story comprehension task, the left posterior superior temporal gyrus (pSTG) showed increased activation with higher fluency levels. This suggests that the learners with higher L2 fluency were actively engaged in post-syntactic integration processing supported by the left pSTG. These data imply that L2 fluency predicts neural resource allocation during language comprehension tasks as well as in production tasks. This study sheds light on the neural underpinnings of L2 learning by identifying the brain regions recruited during different language tasks across different modalities (production vs. comprehension).
authors.affiliation: Division of Cerebral Integration, Department of Cerebral Research, National Institute for Physiological Sciences (NIPS), Aichi, Japan; Department of Physiological Sciences, The Graduate University for Advanced Studies (Sokendai), Aichi, Japan; Research Center for Child Mental Development, University of Fukui, Fukui, Japan; Biomedical Imaging Research Center (BIRC), University of Fukui, Fukui, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Shimada
authors.affiliation: Division of Cerebral Integration, Department of Cerebral Research, National Institute for Physiological Sciences (NIPS), Aichi, Japan; School of Linguistics and Language Studies, and Institute of Cognitive Science, Carleton University, Ottawa, Canada. Electronic address: masako.hirotani@carleton.ca.
authors.forename: M
authors.initials: M
authors.lastname: Hirotani
authors.affiliation: School of Languages and Communication, Kobe University, Kobe, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Yokokawa
authors.affiliation: Department of English Education, Osaka Kyoiku University, Osaka, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Yoshida
authors.affiliation: Division of Cerebral Integration, Department of Cerebral Research, National Institute for Physiological Sciences (NIPS), Aichi, Japan; Department of Physiological Sciences, The Graduate University for Advanced Studies (Sokendai), Aichi, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Makita
authors.affiliation: Division of Cerebral Integration, Department of Cerebral Research, National Institute for Physiological Sciences (NIPS), Aichi, Japan; Research Center for Child Mental Development, University of Fukui, Fukui, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Yamazaki-Murase
authors.affiliation: Division of Cerebral Integration, Department of Cerebral Research, National Institute for Physiological Sciences (NIPS), Aichi, Japan; Department of Physiological Sciences, The Graduate University for Advanced Studies (Sokendai), Aichi, Japan; Division of Psychology, Department of Social and Human Environment, Graduate School of Environmental Studies, Nagoya University, Nagoya, Japan.
authors.forename: H C
authors.initials: HC
authors.lastname: Tanabe
authors.affiliation: Division of Cerebral Integration, Department of Cerebral Research, National Institute for Physiological Sciences (NIPS), Aichi, Japan; Department of Physiological Sciences, The Graduate University for Advanced Studies (Sokendai), Aichi, Japan; Biomedical Imaging Research Center (BIRC), University of Fukui, Fukui, Japan.
authors.forename: N
authors.initials: N
authors.lastname: Sadato
mesh_terms: D000293:Adolescent; D000328:Adult; D001921:Brain / Q000502:physiology*; D001931:Brain Mapping; D032882:Comprehension / Q000502:physiology*; D005260:Female; D006801:Humans; D007807:Language Tests; D007858:Learning / Q000502:physiology; D008279:Magnetic Resonance Imaging; D008297:Male; D019303:Multilingualism; D009483:Neuropsychological Tests; D011932:Reading; D013060:Speech / Q000502:physiology*; D013067:Speech Perception / Q000502:physiology*; D055815:Young Adult
keywords: functional MRI; inferior frontal gyrus; listening comprehension; oral production; second language learning; superior temporal gyrus