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Poster D57, Friday, August 17, 4:45 – 6:30 pm, Room 2000AB

The influence of bilingual language experience on verbal fluency and brain structure and function

Shanna Kousaie1, Shari Baum2,3, Natalie A. Phillips2,4,5, Vincent Gracco2,3,6, Debra Titone2,7, Jen-Kai Chen1,2, Denise Klein1,2;1Cognitive Neuroscience Unit, Montreal Neurological Institute, McGill University, Montreal, QC, H3A 2B4, Canada, 2Centre for Research on Brain, Language and Music, McGill University, Montreal, QC, H3G 2A8, Canada, 3School of Communication Sciences and Disorders, Faculty of Medicine, McGill University, Montreal, QC, H3A 1G1, Canada, 4Department of Psychology/Centre for Research in Human Development, Concordia University, Montreal, QC, H4B 1R6, Canada, 5Bloomfield Centre for Research in Aging, Lady Davis Institute for Medical Research and Jewish General Hospital/McGill University Memory Clinic, Jewish General Hospital, Montreal, QC, H3T 1E2, Canada, 6Haskins Laboratories, New Haven, CT, 06511, USA, 7Department of Psychology, McGill University Montreal, QC, H3A 1G1, Canada

Previous research suggests that bilingualism confers certain advantages in terms of executive control compared to monolinguals; however, importantly, bilingualism has also been associated with disadvantages in some language processes, including lexical retrieval. Poorer lexical retrieval in bilinguals compared to monolinguals is thought to result from competition between the two languages. Within bilinguals, superior performance has been observed in a dominant compared to a non-dominant language, although neuroimaging studies suggest that similar brain regions are implicated in performance across the two languages. Previous studies have compared monolinguals and bilinguals and a native (L1) versus a non-native (L2) language in bilinguals, leaving a gap in the literature with respect to how differences in L2 language experience may impact lexical retrieval. Specifically, how might lexical retrieval differ in relation to when the L2 was learned, or the attained proficiency in the L2? In the current investigation, we examined verbal fluency (letter/phonemic fluency and category/semantic fluency) in a highly-controlled group of French/English bilinguals. Two groups of participants who were matched in terms of relevant demographic variables as well as general cognitive ability and differed only with respect to when they learned their L2 (17 participants learned their two languages from birth, while 16 participants learned their second language after age 6) underwent structural and resting-state magnetic resonance imaging (MRI) and completed a battery of language and cognitive tasks. Of interest for this investigation is performance on the letter and category fluency tasks, which all participants completed in both English and French. Behaviourally, the groups did not differ in terms of the number of exemplars generated in L1 or in L2 for either letter or category fluency, although performance was better for category compared to letter fluency in both languages, and in L1 compared to L2 for both tasks. Surprisingly, participants performed comparably regardless of when they learned their L2. A whole-brain analysis of grey matter volume (GMV) also revealed no group differences in GMV. However, a whole-brain analysis of GMV in relation to performance revealed a positive association between brain structure and performance in L2 only. Specifically, GMV in the right posterior cerebellum and the left supplementary motor area was associated with better performance in L2 letter and category fluency, respectively, demonstrating that GMV was related to individual differences in performance irrespective of when the L2 was learned. Additionally, we compared GMV in a priori regions of interest based on the literature and found that simultaneous bilinguals had greater GMV compared to late bilinguals in left inferior temporal cortex and bilateral caudate nuclei. Analyses examining resting-state functional connectivity between these regions and the rest of the brain will add to the structural findings by determining the functional networks that are implicated in lexical retrieval, and how these may differ as a function of language and/or L2 language experience. These findings will help to elucidate a more refined understanding of how individual differences in language experience influence language processing, and lexical retrieval more specifically, in both an L1 and an L2.

Topic Area: Multilingualism