Tiny changes: exploring bilingualism through NODDI and insights into microstructural plasticity

Poster Session A - Saturday, April 13, 2024, 2:30 – 4:30 pm EDT, Sheraton Hall ABC

Imola X MacPhee¹, John AE Anderson; ¹Carleton University, Ottawa, Canada

Bilingualism leads to macrostructural gray matter changes in the brain, however, the ability to quantify changes in microstructural gray matter has been limited. Here, we use Neurite Orientation Dispersion and Density Imaging (NODDI), a multi‐shell diffusion Magnetic Resonance Imaging (MRI) technique, to estimate dendritic complexity in bilinguals. This method can directly test the Dynamic Restructuring Model (DRM), which proposes that dendritic reorganization occurs during language learning, followed by pruning once the language is mastered. Additionally, microstructural changes can be used to explore bilingualism-induced cognitive reserve in aging. To date, twenty-three (n=23) English-French bilinguals have been assessed using language and cognition measures and scanned using 3T MRI. Preliminary results using Partial Least Squares Correlation revealed that the Orientation Dispersion Index (ODI), a proxy for dendritic branching, was associated with 3 latent variables capturing 1) second language proficiency and age of acquisition (AoA); 2) cognitive performance; and 3) an exploratory domain of speech perception in noise. Lower AoA and higher proficiency were associated with reduced ODI in multiple language-related regions, consistent with the DRM and neural efficiency. Conversely, higher cognition was associated with reduced ODI in memory-related regions, but increased in sensory regions. Further analyses will include additional NODDI metrics, including free water and neurite density indices, to gain a more complete picture of cortical composition and myelination. Together, these metrics should provide insight into the subtleties of language-related neuroplasticity. The results are part of a planned, multi-phase longitudinal study to assess the impact of bilingualism on cognition in aging.

Topic Area: LANGUAGE: Development & aging