Cognitive and brain reserve in bilinguals: field overview and explanatory mechanisms

There is an ongoing debate on potential neuroprotective effects of bilingualism against cognitive decline during healthy aging. In this paper, we consider the neural and cognitive mechanisms through which these protective effects may operate. We review the evidence suggesting that bilingualism can act as a booster of neuroplasticity and/or as a brain protection mechanism providing effective compensation. Our main aim is to better define the linkage between reserve and lifetime bilingual experience and their effects on the mind and brain. We first illustrate the concept of reserve and contextualize existing results of bilingualism research within the reserve framework. Then, we discuss how bilingualism-induced enhancements of certain cognitive functions may constitute the basis for the neural underpinnings of reserve, i.e., brain reserve (BR) and cognitive reserve (CR). Finally, we discuss how the interplay between BR and CR fostered by multiple language use can provide protection to the aging brain.