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Structural differences in the cortex and subcortex between healthy aging bilinguals and monolinguals from the Human Connectome Project

Poster D47 in Poster Session D with Social Hour, Friday, October 7, 5:30 - 7:15 pm EDT, Millennium Hall
Also presenting in Poster Slam D, Friday, October 7, 5:15 - 5:30 pm EDT, Regency Ballroom

Monika M. Polczynska1, Letzi Esparza1, Yuchen Cui1, Taylor Wishard1, Alexandra Klomhaus1, Leanna Hernandez1, John Anderson2, Mirella Diaz-Santos1, Ellen Bialystok3, Susan Y. Bookheimer1; 1University of California, Los Angeles, 2Carleton University, Ottawa, 3York University, Toronto

Introduction: There has been a tremendous increase in studies examining how bilingualism changes the structure of the brain (Liu et al. 2021). In this study, we accessed a database of over 1200 healthy aging adults from the Human Connectome Project (Bookheimer et al. 2019) to examine cortical and subcortical brain structure in bilinguals compared to monolinguals. Based on several recent models of brain restructuring in bilinguals (e.g., DeLuca et al. 2020; Pliatsikas et al. 2019; Grundy et al. 2017), we hypothesized that, compared to monolinguals, bilinguals would have smaller anterior brain regions and larger posterior (cortical and subcortical) brain areas. Methods: Using a brain atlas with detailed parcellations (HCP-MMP v1.0 cortical atlas, Glasser et al. 2016), we measured cortical surface area, thickness, and volume in bilinguals and monolinguals. Subcortical volume was extracted with the Automatic Subcortical Segmentation atlas (Fischl et al. 2002). Following prior work (Anderson et al. 2018), we applied propensity score matching to match bilinguals and monolinguals on five confounding variables: sex, handedness, age, education, and MRI scanner ID (160 bilinguals, 169 monolinguals; mean age: 56 years). In addition, we also report comparisons between a subset of bilinguals that included active (i.e., currently using their languages) proficient bilinguals with at least 10 years of language experience in their second language and matched monolinguals (35 participants per group, mean age: 51 years). Based on previous literature, we selected 34 of 180 regions of interest (ROIs) per hemisphere from the multi-modal parcellation of the HCP-MMP atlas (Glasser et al. 2016) that centered around six larger structures: the inferior frontal gyrus, middle temporal gyrus, anterior temporal lobe, superior posterior temporal lobe, the inferior parietal cortex, and anterior cingulate cortex (e.g., Ressel et al. 2012). Seven structures were chosen from the subcortical atlas (Burgaleta et al. 2015). All statistical analyses were completed using R and RStudio (version 2021.9.0.351). One-way analysis of variance tested for differences in the three cortical parcellation measures (34 ROIs each), and differences in volume for the subcortical ROIs. P-value adjustments were performed using Benjamini and Hochberg correction for false discovery rate (two-sided alpha <0.05). Results: Relative to monolinguals, bilinguals from the primary matched sample had less cortical area and thickness in the anterior ROIs, more thickness in the posterior ROIs, and the same cortical and subcortical volume. We observed robust differences between the subset of active proficient bilinguals and monolinguals for surface area, thickness, and cortical and subcortical volume. Specifically, we report: (a) smaller values for the three cortical measures in the anterior ROIs (e.g., area a24 in the left anterior cingulate cortex, q=0.03), (b) larger values in the posterior ROIs (e.g., area LBelt in the right auditory cortex, q=0.01). Conclusion: We used detailed brain parcellations to examine differences in the cortex and subcortex in bilinguals and monolinguals from the Human Connectome Project in Aging study. Our findings confirm the predictions of the bilingual restructuring models showing that bilinguals have smaller anterior brain areas and larger posterior structures than monolinguals.

Topic Areas: Multilingualism, Control, Selection, and Executive Processes

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