Sound to Language: Different Cortical Processing for First and Second Languages in Elementary School Children as Revealed by a Large-Scale Study Using fNIRS

Abstract

A large-scale study of 484 elementary school children (6–10 years) performing word repetition tasks in their native language (L1-Japanese) and a second language (L2-English) was conducted using functional near-infrared spectroscopy. Three factors presumably associated with cortical activation, language (L1/L2), word frequency (high/low), and hemisphere (left/right), were investigated. L1 words elicited significantly greater brain activation than L2 words, regardless of semantic knowledge, particularly in the superior/middle temporal and inferior parietal regions (angular/supramarginal gyri). The greater L1-elicited activation in these regions suggests that they are phonological loci, reflecting processes tuned to the phonology of the native language, while phonologically unfamiliar L2 words were processed like nonword auditory stimuli. The activation was bilateral in the auditory and superior/middle temporal regions. Hemispheric asymmetry was observed in the inferior frontal region (right dominant), and in the inferior parietal region with interactions: low-frequency words elicited more right-hemispheric activation (particularly in the supramarginal gyrus), while high-frequency words elicited more left-hemispheric activation (particularly in the angular gyrus). The present results reveal the strong involvement of a bilateral language network in children’s brains depending more on right-hemispheric processing while acquiring unfamiliar/low-frequency words. A right-to-left shift in laterality should occur in the inferior parietal region, as lexical knowledge increases irrespective of language.

Neural mechanisms of language switch

“…In late bilinguals who have asymmetric proficiency between languages, the right PFC may play a part in switching between languages with selection of phonological representations from the non-dominant language lexicon. Additionally, a recent study reported that acquiring unfamiliar words, an important ability for second language learning, elicited more right prefrontal activation than left in children (Sugiura et al, 2011). The present study has shown for the first time that the engagement of the right PFC in language switching processes may be proficiency dependent.…”

10. Language acquisition and brain development: Cortical processing of a foreign language

“…First, the advantage of HOE over AOFE is somewhat unexpected because the effects of AOFE have Language acquisition and brain development been reported repeatedly in previous behavioral studies (Yamada, Takatsuka, Kotake andKurusu 1980: Johnson andNewport 1989;DeKeyser 2000), supporting the advantages of early starters in phonological skills and syntax learning. The discrepancy of the results in the previous behavioral studies and those in Ojima, Matsuba-Kurita et al (2011) might be due to different phases or stages of learning. Previous behavioral studies on ongoing L2/FL learning have reported that late starters are faster learners than early starters even in syntax, suggesting the advantage of late starters in the speed of learning (Munoz 2006;Snow and HoefnagelHohle 1978).…”

“…environment, and learning strategy. Ojima, Matsuba-Kurita et al (2011) focused on the age of first exposure (AOFE) and total hours of exposure (HOE). Based on a total of 815 ERP datasets obtained longitudinally from 350 children who participated in the cohort study, children's English proficiency scores and N400 amplitude were analyzed in multiple regression analyses.…”

“…We have already known that, in adults, L1 transfer of the morphological representation systems affect the neural mechanisms underlying L2 morphosyntactic processing (Wakabayashi et al 1997;Tatsuta and Hagiwara 2012). As the ERP data in Ojima, Nakamura et al (2011) andOjima, Matsuba-Kurita et al (2011) were obtained while children processed one word, future ERP research on L2 syntax must take into account possible effects of L1 transfer in the children and adolescents.…”

“…Literature dealing with L2 acquisition is even more scarce, although studies dealing with older children have been conducted (Sakai et al 2004;Tatsuno and Sakai 2005;Sakai et al 2009). Using fNIRS as a data acquisition tool and a basic word repetition task as a predictor of language learning ability, Sugiura et al (2011) explored the different characteristics of language-related regions of interest (ROIs) and hemispheric laterality with respect to L1 and L2 processing of word frequency (high and low) in developing brains of school-age children. The participants are the same as those in the cohort study mentioned above, but the analysis is a cross-sectional examination of the data obtained from the middle year of the cohort study.…”