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Auteur: Noriaki YUSA

Co-Auteur(s): Masatoshi KOIZUMI, Tohoku University, Japan Jungho KIM, Tohoku University, Japan

Social Interaction Affects the Neural Measures of Syntactic Processing: Evidence from fMRI

Abstract/Résumé: Introduction: Children acquire a language used around them, but less trivial is the fact that they do so from people: children fail to acquire a language from TV, or computer presentations (Baker 2001). At the earliest phases of language acquisition social interaction is essential for phonetic learning (Kuhl 2007). No study, however, has yet examined how social interaction during second language acquisition of syntax in adulthood will affect the neural mechanisms. Recent neuroimaging studies show that comprehension of spoken languages and sign languages activates the classical language brain regions including the left inferior frontal gyrus(IFG) (Sakai et al. 2005). The present study shows, by examining the acquisition of Japanese sign language under two different social learning conditions, that learning through interaction with a deaf signer resulted in the change in the activation of the left IFG. Methods: Japanese adults who had never learned Japanese sign language (JSL) participated in JSL training through (A) social interaction with a native deaf signer [live-exposure group], or (B) the DVDs that videotaped the instruction in (A) [DVD-exposure group]. Therefore, the difference between (A) and (B) was the existence of social interchanges through a live human. Results and Conclusions: Performance of the live-exposure and the DVD-exposure groups did not differ. In contrast, fMRI measures revealed striking differences in neural activities between two groups. Significant activations in the left inferior frontal gyrus (LIFG) were found only for the live-exposure group. No significant cortical activation change, by contrast, was found for the DVD-exposure group, who experienced the same visual input for the same duration via the DVD presentations. This shows that (superficially) similar performance between the groups “does not necessarily implicate reliance on similar neural mechanisms” (Morgan-Short et al. 2012). Given that the LIFG is involved in the syntactic processing of language, spoken or signed, only training in an interactional setting resulted in an fMRI signature typical of native speakers: activation of the LIFG. This study provides the first neuroimaging data to show that a human being's presence in learning L2 syntax causes changes in the brain. This suggests that in addition to early speech learning (Kuhl 2007), social interaction is crucial in order for L2 learners to come to rely on native-like neural mechanisms in processing syntax. Social interaction through the interchanges with a native deaf signer may make it easier to "crack the JSL code", neurologically supporting the view that “language is a social product” (Saussure 1916/1972).