| 其他摘要 | Background：Aging is usually accompanied by cognitive decline. Accelerated cognitive decline will lead to neurodegenerative diseases such as Alzheimer's disease (AD). With the aging of the population, preventing and delaying the occurrence and development of AD has become a social concern. Recent studies have shown that bilingualism protect brain function, which is mainly reflected in delaying the decline of executive function and increasing the plasticity of brain structure and function. Learning and using an additional language may be an effective way to delay cognitive aging in the elderly. However, many studies failed to take the influenced factors of bilingualism (i.e., the individual's age, acquisition age of the second language, proficiency and frequency of usage) into account. In the present study, we overcame these limitations by analyzing the contribution of bilingualism on performance of executive function and the brain mechanism. In addition, we also explored the feasibility of bilingualism in preventing AD.
Method: We explored the relationship between bilingualism and executive function based on the Human Connectome Project in Aging (HCP-A). We hypothesized that bilingualism protects against age-related cognitive deterioration and improves the plasticity on the structure and function in related brain regions, which may help to prevent the occurrence of AD. Multivariate variance analysis and t-test were used to compare the difference of executive function’s performance and the changes of age- related bilingual advantage between monolinguals and bilinguals. We also analyzed the differences of structure and function on the brain between them and calculated the correlation between the differences and the performances of executive functions. The possibility of bilingualism preventing AD was explored based on changes of FC in DMN and hippocampus.
Results: (1) The results of performances on executive functions showed early acquisition age can better protect executive function. Compared with late bilinguals, the inhibition ability and cognitive flexibility of early bilinguals were significantly better and their bilingual advantages were significant in adults from 36 to 59 years old, especially in 45 to 59. (2) The results of brain structure showed bilinguals (especially in skilled bilinguals) increased the volume of gray matter and cortical thickness in DMN (i.e., angular gyrus and cuneus), frontal parietal network (FPN) (i.e., middle frontal gyrus, middle cingulate gyrus, inferior temporal gyrus, middle temporal gyrus), Somatomotor network (SMN) (i.e., precentral gyrus, postcentral gyrus, supplementary motor area) and gray matter volume in cerebellum, fusiform gyrus and putamen, which might help to improve the performance of executive function. The results of FC indicated that early bilinguals showed decreased FC in middle frontal gyrus, angular gyrus and inferior parietal lobule (IPL) compared to those later learners, and FC intensity in angular gyrus and middle frontal gyrus was negatively correlated with cognitive flexibility, which indicating that there were less neural resources involved in executive function in early bilingualism. Bilingualism increased the global efficiency of FPN such as middle frontal gyrus, inferior frontal gyrus and cingulate gyrus, which were significantly positively correlated with executive functions. The results showed that bilinguals rely on FPN to process language information and executive function. (3) The feasibility of bilingualism in preventing AD showed FC of bilinguals increased in left IPL and left hippocampus, also with left IPL and right hippocampus in early learners and left IPL and bilateral hippocampus in skilled learners. The results suggested that the increase of FC may be an internal neural mechanism to slow down cognitive decline and help to compensate for the decline of executive function caused by aging.
Conclusion: The results further clarified that bilingualism delays the decline of executive function, and the early age of acquisition and early acquisition age has a better protective effect on executive function. The increase of gray matter volume and cortex thickness of DMN FPN SMN and the global efficiency of FPN may be the internal neural mechanism supporting bilingual advantages. The results of correlation analysis suggested that DMN and FPN may be brain mechanisms that coincide between language control and general cognitive control in bilinguals, and that the cerebellum, fusiform gyrus, and putamen may be specific brain regions that bilinguals engage in increased FC of IPL in DMN suggested that bilingualism may help to prevent AD. In a word, our findings provided evidence for bilingualism to increase brain reserve and protect against age-related cognitive deterioration. bilingual control different from those involved in general cognitive control. The increased FC of IPL in DMN suggested that bilingualism may help to prevent AD. In a word, our findings provided evidence for bilingualism to increase brain reserve and protect against age-related cognitive deterioration. |
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