Gray Matter Volume as Evidence for Cognitive Reserve in Bilinguals With Mild Cognitive Impairment.

Abstract

Compared with monolinguals, bilinguals have a later onset of mild cognitive impairment (MCI) and Alzheimer disease symptoms and greater neuropathology at similar cognitive and clinical levels. The present study follows a previous report showing the faster conversion from MCI to Alzheimer disease for bilingual patients than comparable monolinguals, as predicted by a cognitive reserve (CR). Identify whether the increased CR found for bilinguals in the previous study was accompanied by greater gray matter (GM) atrophy than was present for the monolinguals. A novel deep-learning technique based on convolutional neural networks was used to enhance clinical scans into 1mm MPRAGEs and analyze the GM volume at the time of MCI diagnosis in the earlier study. Twenty-four bilingual and 24 monolingual patients were diagnosed with MCI at a hospital memory clinic. Bilingual patients had more GM loss than monolingual patients in areas related to language processing, attention, decision-making, motor function, and episodic memory retrieval. Bilingualism and age were the strongest predictors of atrophy after other variables such as immigration and education were included in a multivariate model. CR from bilingualism is evident in the initial stages of neurodegeneration after MCI has been diagnosed.