Neural correlates of cognitive resilience differ between experiences of bilingualism and education: A cortical surface‐based morphometry study in dementia

Abstract

AbstractBackgroundLife‐course experiences such as education and bilingualism can be protective against dementia. The cognitive effects of bilingualism are specific while education has a more pervasive effect on general cognitive abilities, indicating that there is a likelihood of a variability in mechanisms underlying resilience. India is characterised by educational diversity and bilingualism. Importantly, bilingualism is not always associated with confounding effects of education, socioeconomic class or immigration. This makes the population uniquely suited for the study of resilience and opens up the possibility to disentangle the independent effects of bilingualism and education. Recent evidence indicates that surface‐based morphometric features of the cortical thickness and surface area are significantly modulated by life course experiences. Therefore, in this study, the independent influence of bilingualism and education on cortical thickness and surface area in dementia were studied to investigate the mechanisms that underlie resilience.MethodForty‐five patients with Frontotemporal dementia (FTD) were enrolled. 27 bilinguals were matched with 18 monolinguals for demographic factors and clinical severity. We examined the independent associations of bilingualism and education with cortical thickness and surface area using a surface based morphometric approach.ResultBilinguals with FTD had greater cortical thickness and reduced surface area in bilateral dorsolateral and medial frontal areas, and right parietotemporal cortex, regions associated with executive control. Bilinguals also demonstrated lesser cortical thickness in the language processing areas of left superior temporal, inferior parietal and lateral occipital regions compared to monolinguals. On the other hand, higher education was associated with decreased cortical thickness and increased surface area in bilateral frontal, medial temporal, parietal, occipital, and left temporal regions.ConclusionThis study explores for the first‐time, associations of two different proxies of resilience with cortical thickness and surface area in FTD. Our findings indicate that the neural substrate underlying the protective effects of bilingualism differ from education in FTD, and can be related to their differential effects on cognition. Results indicate specific neural correlates of resilience for different life‐course experiences.