Bilingualism and dementia: neural mechanisms and implications for cognitive reserve

Abstract

Multiple studies have found that bilinguals show the first symptoms of dementia later than monolinguals. Therefore, it is hypothesized that bilingualism could protect against dementia, but the neural bases of this protective effect are still unclear. In the works included in this thesis, we studied the neural mechanisms of bilingualism and dementia, and its implications for cognitive reserve, obtaining magnetic resonance images of bilingual and monolingual patients in different stages of Alzheimer’s disease (AD) and of healthy participants. We found that the neural bases of bilingualism’s protection against dementia could be the use of alternative brain circuits as a mechanism of compensation, in the presence of more structural atrophy in fibers and regions related to AD pathology, resulting in similar levels of cognitive impairment. This protection seems to start in prodromal AD stages and be maintained longitudinally until the disease starts.