Abstract：
Cognitive Reserve (CR) refers to the preservation of cognitive function in the face of age- or disease-related neuroanatomical decline. While bilingualism has been shown to contribute to CR, the extent to which, and what particular aspect of, second language experience contributes to CR are debated, and the underlying neural mechanism(s) unknown. Intrinsic functional connectivity reflects experience-dependent neuroplasticity that occurs across timescales ranging from minutes to decades, and may be a neural mechanism underlying CR. To test this hypothesis, we used voxel-based morphometry and resting-state functional connectivity analyses of MRI data to compare structural and functional brain integrity between monolingual and bilingual older adults, matched on cognitive performance, and across levels of second language proficiency measured as a continuous variable. Bilingualism, and degree of second language proficiency specifically, were associated with lower gray matter integrity in a hub of the default mode network - a region that is particularly vulnerable to decline in aging and dementia - but preserved intrinsic functional network organization. Bilingualism moderated the association between neuroanatomical differences and cognitive decline, such that lower gray matter integrity was associated with lower executive function in monolinguals, but not bilinguals. Intrinsic functional network integrity predicted executive function when controlling for group differences in gray matter integrity and language status. Our findings confirm that lifelong bilingualism is a CR factor, as bilingual older adults performed just as well as their monolingual peers on tasks of executive function, despite showing signs of more advanced neuroanatomical aging, and that this is a consequence of preserved intrinsic functional network organization.
摘要：
认知储备（CR）是指在面对与年龄或疾病相关的神经解剖学衰退时保持认知功能。虽然双语已被证明有助于CR，在多大程度上,以及哪个特定方面，第二语言经验对CR的贡献有争议，和潜在的神经机制未知。内在功能连接反映了经验依赖性神经可塑性，这种神经可塑性发生在从几分钟到几十年的时间尺度上。可能是CR的神经机制。为了检验这个假设，我们使用基于体素的形态计量学和MRI数据的静息状态功能连接分析来比较单语和双语老年人的脑结构和功能完整性,与认知表现相匹配，以及作为连续变量衡量的不同水平的第二语言能力。双语,特别是第二语言水平，与默认模式网络中心的灰质完整性较低相关-该区域特别容易受到衰老和痴呆症的影响-但保留了固有的功能网络组织。双语主义缓和了神经解剖学差异和认知能力下降之间的联系，因此，较低的灰质完整性与较低的执行功能有关，但不是双语者.内在功能网络完整性在控制灰质完整性和语言状态的群体差异时可以预测执行功能。我们的发现证实，终身双语是一个CR因素，就像双语老年人在执行功能任务上的表现一样，尽管显示出更高级的神经解剖学衰老的迹象，这是保留了内在功能网络组织的结果。
