Bilingualism and “Brain Reserve”: A Matter of Age

There is a lively debate whether bilingualism as a state of permanent cognitive control contributes to so-called brain reserve, thus delaying the onset of symptoms associated with neurodegeneration by up to 5 years. Here, we address this question in a large-scale (n=399) population-based study. We compared the grey matter volume of mono- vs. bilinguals in the left inferior frontal (IFG) and inferior parietal (IPL) cortex, and its modulation by biological age. Three core findings emerged: (1) Brain volume was systematically higher in bi- than monolinguals. (2) This difference disappeared at higher ages, and the slope of decline was steeper for bi- than monolinguals. (3) The volume difference between age groups disappeared in the IFG at earlier ages than in the IPL. Thus, bilingualism might indeed contribute to brain reserve in older age, with posterior regions showing a particular resilience to atrophy and thus less necessity for functions to shift to anterior control regions