Effects of bilingualism on white matter atrophy in mild cognitive impairment: a diffusion tensor imaging study

Abstract

Background and purpose:Previous investigations show that bilinguals exhibitthe first symptoms of dementia 4–5 years later than monolinguals. Therefore,bilingualism has been proposed as a cognitive reserve mechanism. Recent stud-ies have advanced towards an understanding of the brain mechanisms underly-ing bilingualism’s protection against dementia, but none of them deals withwhite matter (WM) diffusion.Methods:In this study, the topic was investigated by measuring WM integrityin a sample of 35 bilinguals and 53 passive bilinguals with mild cognitiveimpairment.Results:No significant differences were found between the groups in cognitivelevel, education, age or sex. However, bilinguals showed higher mean diffusiv-ity in the fornix, but higher fractional anisotropy, lower mean diffusivity, axialdiffusivity and radial diffusivity in the parahippocampal cingulum, and lowerradial diffusivity in the right uncinate fasciculus. Significant correlations werealso found between WM integrity in the left parahippocampal cingulum andthe Boston Naming Test in passive bilinguals.Conclusions:These results suggest that bilingualism contributes to a differen-tial pattern of WM disintegration due to mild cognitive impairment in fibersrelated to bilingualism and memory.