Bilingualism's Effects on Resting-State Functional Connectivity in Mild Cognitive Impairment

Abstract

Background:

Bilingualism is considered a cognitive reserve (CR) factor, due to the delay in the onset of dementia in bilinguals compared with monolinguals. Two neural mechanisms have been suggested to underlie CR: neural reserve and neural compensation. However, it is still unclear how bilingualism contributes to these mechanisms.

Methods:

In this study, we used cognitive tests, functional connectivity (FC), regional homogeneity, and fractional amplitude of low-frequency fluctuations (fALFF) measures to study resting-state brain patterns in a sample of bilingual and monolingual subjects with mild cognitive impairment.

Results:

We found no significant differences between the groups in age, sex, education, or cognitive level, but bilinguals showed higher FC than monolinguals between the posterior part of the superior temporal gyrus and the precuneus, positively correlated with Mini-Mental State Examination scores, and higher fALFF in the thalamus bilaterally.

Conclusions:

Our results suggest that bilingualism may act as a CR factor that protects against dementia through neural compensation.

Impact statement

Recent investigations suggest that neural compensation is one of the cognitive reserve mechanisms underlying the protection of bilingualism against dementia. Although brain changes in functional connectivity (FC) have been proposed as evidence of this mechanism, no study has directly used FC to study neural compensation in bilingualism. Our findings show that mild cognitive impairment bilinguals manifest higher resting-state FC than monolinguals between the language network and the precuneus, supporting the involvement of neural compensation in the protection of bilingualism against dementia. Moreover, we found bilingualism effects in the spontaneous activity of the thalamus, a region related to atrophy in dementia.