Presentation
Search Abstracts | Symposia | Slide Sessions | Poster Sessions | Poster Slams
Cortical Thickness is Related to Variability in Bilingual Language Proficiency
Poster A56 in Poster Session A, Thursday, October 6, 10:15 am - 12:00 pm EDT, Millennium Hall
My Nguyen1, Kelly Vaughn2, Arturo Hernandez1; 1University of Houston, 2University of Texas Health Science Center at Houston
Historically, research has tried to understand how language networks in the brain develop in monolinguals (i.e., people who know a single language), but increasingly, research is focusing on language network development in bilinguals (i.e., people who know two languages). Research suggests that bilingual experience is associated with grey matter changes such that initial language gains are associated with grey matter expansion and language expertise is associated with grey matter renormalization. Previous studies on language skill development primarily focused on between-subjects, quasi-experimental comparisons of monolinguals and bilinguals. This study proposes a new paradigm to examine language expertise and cortical thickness within bilinguals (n = 215), as well as between bilinguals and monolinguals (n = 145). Cortical thickness was chosen as the measure of grey matter because of its experience-dependent development. Data was combined from eight different studies; thus, language skill was assessed using the Boston Naming Test and/or the Woodcock-Muñoz Language Survey – Revised picture vocabulary subtest along with either the passage comprehension subtest or listening comprehension subtest. Performance on these measures was calculated as a proportion (total correct/total possible), and when participants completed more than one of these measures, their percentages for each measure were averaged to create a total measure of language skill. Several two-tailed general linear models were conducted in each hemisphere to analyze the data for the current study, each with cortical thickness as the outcome variable. Analyses were conducted in all participants with English language skill and language group (monolingual vs. bilinguals) as the predictors and SES as the covariate. Other analyses were conducted within language group, with one model focused on English monolinguals with English language skill as the predictor and SES as the covariate, and the second model focused on Spanish-English bilinguals with English or Spanish proficiency as the predictor, controlling for the other language proficiency, English age of acquisition, and SES. A Monte Carlo simulation was applied to each general linear model to correct for multiple comparisons when determining significant clusters. In general, results highlight variability within bilinguals, finding relationships between cortical thickness and English proficiency that are relatively consistent within monolinguals, but inconsistent within bilinguals. Across all participants, higher levels of proficiency in English—monolinguals’ only language and bilinguals’ second but stronger language—were negatively related to cortical thickness in various frontal, temporal, and parietal regions. Moreover, there was an interaction between language group and English skills in predicting cortical thickness, such that monolinguals showed a stronger relationship between English proficiency and thickness than bilinguals in the caudal middle frontal gyrus and the superior frontal gyrus. Within bilinguals, language skill in L1 (Spanish) was positively correlated with cortical thickness in frontal and parietal regions, while language skill in L2 (English) was negatively correlated with cortical thickness in frontal regions. Findings also show differing lateralization within the bilingual brain, such that L2 (English) is more left-lateralized than L1 (Spanish). Future directions for cognitive-developmental neuroscience research in bilinguals are suggested.
Topic Areas: Multilingualism, Development