The impact of bilingualism on brain structure and function in Huntington's disease

Abstract

Introduction: Bilingualism exerts neuroprotective effects against neurodegeneration. In Huntington's disease (HD), the systems involved in bilingual control show early compromise, but the effect of bilingualism on the course of HD is unknown. Methods: We addressed the impact of livelong use of bilingualism on the clinical features, brain structure and function in 30 early-mild stage HD patients. Using voxel-wise regression analysis, we explored the effect of levels of use of bilingualism on grey-matter volume (GMV) and 18F-FDG metabolism. Results: Higher use of bilingualism was associated with better performance in inhibitory control and set-shifting independently of age and education and with higher GMV in the inferior frontal gyrus. 18F-FDG data revealed a significant effect on multiple fronto-temporal regions, specifically, in the dorsal anterior cingulate cortex, the anterior insula, the ventromedial orbital prefrontal cortex and the inferior frontal gyrus. These changes contributed to better inhibitory control and set-shifting and to more preserved motor and functional capacity. Conclusion: In HD, lifelong use of bilingualism is associated with structural and metabolic brain changes that have an impact on cognition, movement and functionality. These findings highlight the importance of stimulating cognitive and brain reserve in HD and in other neurodegenerative conditions.