Poster C54, Friday, August 17, 10:30 am – 12:15 pm, Room 2000AB
Bilingualism is a Spectrum: Effects of specific language experiences on brain function and executive control in bilinguals.
Vincent DeLuca1, Christos Pliatsikas1, Jason Rothman1,2, Ellen Bialystok3;1University of Reading, UK, 2UiT: The Arctic University of Norway, 3University of York, Canada
The effects of bilingualism on executive control are heavily debated, given the variable results found across studies (Valian, 2015). However, discrepancies between bi-/monolinguals likely correlate to how bilinguals are treated as a monolithic group (Bak, 2016; Surrain and Luk, 2017). Theories state that individual bilingual language experiences confer shifting language control demands and that the mind/brain adapts accordingly (Green and Abutalebi, 2013; Grundy et al., 2017). However, few studies have specifically examined effects of individual differences in bilingual language use on executive control processes and their neural correlates. We address this by examining a range of specific experience-based factors (EBFs) within the bilingual experience and their effects on brain function related to executive control processes. We assess the hypothesis that specific EBFs will confer distinct effects in regions specific to language/executive control processes. Typically developing bilinguals (n= 65, 49 female, Mage= 31.8yrs, SD 7.59) were scanned (MRI) while they completed a Flanker task which contained mixed blocks (congruent and incongruent trials), a congruent block, and a neutral block. Participants also completed an English proficiency test (Oxford QPT; Geranpayeh, 2003), and a detailed language use/background questionnaire (LSBQ; Anderson et al., 2017). LSBQ scores were used to predict both task performance and neural recruitment. Five predictors were included in the model: length of second language (L2) immersion, L2 Age of Acquisition (L2 AoA), a weighted composite factor score representing the extent of active engagement with both languages (Bilingualism composite score, BCS), and two factor scores detailing degree of L2 use in 1) social/community settings (L2_Social) and 2) home settings (L2_Home). Behavioral analyses showed significant differences in reaction times (RTs) between different trial/block types on the Flanker task (all ps<.0001). RT differences were not significantly predicted by the language demographics (all ps>0.05). However, the predictors showed activation in distinct and specific regions in terms of neural recruitment; activations differences related to the mixing cost (mixed compared to neutral blocks) were modulated in specific ways by each factor from the LSBQ. Longer L2 immersion predicted increased activation in several regions including the left inferior frontal gyrus (LIFG), left precentral gyrus, and right supramarginal gyrus (p<.05, corrected). This indicates recruitment of a more broadly distributed language/executive control network commensurate with a longer duration of intensive L2 exposure (Abutalebi and Green; 2016). The factor scores L2_Home and L2_Social were found to positively correlate with increased activation in several portions of the cerebellum (p<.05, corrected). This indicates a shift toward automated language/executive control processing commensurate with the degree of engagement with the L2 in the immersive environment. Other data are discussed in light of how the brain optimizes specifically to handle language/executive control demands incurred by differing bilingual language experiences. More broadly, this approach highlights the need to consider several specific language experiences in assessing the neurocognitive effects of bilingualism. In turn, by beginning to reveal/understand the dynamics of the bilingual experience and how this manifests in adaptations to cognitive functions, we will contribute to a better understanding of the variability reported in the literature.
Topic Area: Multilingualism