Presentation
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A multifactorial approach to study bilingualism: Evidence from structural and functional neuroimaging
Poster B17 in Poster Session B and Reception, Thursday, October 6, 6:30 - 8:30 pm EDT, Millennium Hall
Tanya Dash1, Yves Joanette1, Ana Ines Ansaldo1; 1CRIUGM
Healthy aging is associated with declines in cognitive performance associated with lifelong changes in structural and functional characteristics of the brain. Bilingualism tends to protect against these age-related changes. This study compared brain and behavioral outcomes for cognitively healthy bilingual adults. Unlike previous studies, the effects of bilingualism were examined along a continuum instead of dichotomizing them. This study explores the effects of bilingualism on the cortical surface area and resting-state functional connectivity (rsFC). While the impacts of bilingualism on cognitive processes across the lifespan have been documented, the understanding of bilingualism-related neural substrate is limited. The current study (N = 75; Age range = 30-80 years; Female = 46) investigated structural differences in bilingual participants varying on a continuum of measures of bilingualism. A multifactorial approach to studying bilingualism resulted in 4 latent variables – L2 exposure, L2 proficiency, L2, objective task performance, and L2 age of acquisition (AoA), which were used as measures of bilingualism. We examined global differences in cortical grey matter areas due to bilingualism, age, and other cognitive reserve factors. L2 language exposure predicted the cortical surface area of Rt PCC; cortical grey matter surface area increases with increasing L2 exposure with no influence of age and other cognitive reserve variables. L2 objective task performance and L2 AoA were able to positively predict cortical surface areas of the right orbital frontal and rt superior frontal areas, accompanied by a negative effect of chronological age. L2 AoA and age negatively impact cortical surface areas of Lt middle temporal, Lt parahippocampal, Rt transverse temporal, and Rt pars orbitalis. L2 objective task performance positively predicts change in cortical surface area of Lt PCC and Lt rostral ACC. Cognitive reserve variables had no impact on cortical surface areas; however, there was a reduction in cortical areas with an increase in chronological age. The interaction between these variables will be discussed in detail. These results suggest that bilinguals showed greater cortical surface areas with an increasing level of bilingualism in key regions related to language and executive control function, regardless of age-related widespread GM deterioration. We also explored the impact of bilingualism on rsFC networks using the four latent variables and found a differential impact of bilingualism on the rsFC matrices while controlling for the effects of age and other cognitive reserve variables. Specifically, rsFC between default mode network and control network varied with different levels and measures of bilingualism. The objective measure of bilingualism positively modulates the rsFC between the left salience ventral attention network and the right salience ventral attention network. The subjective measures of bilingualism showed a differential correlation between the default mode network and the control network. L2 exposure negatively modulates DMN-control network connectivity, and L2 proficiency showed a positive correlation. Such differential nature of the impact of bilingualism on the rsFC between DMN-control networks emphasizes the dynamic nature of bilingualism that is tapped by considering bilingualism on a continuum and using the multifactorial approach to study bilingualism.
Topic Areas: Multilingualism, Control, Selection, and Executive Processes