Department of Psychology, University of California, Riverside, CA, USA.
Institute for Memory Impairments and Neurological Disorders, University of California, Irvine, CA, USA; Department of Neurology, University of California, Irvine, CA, USA; Department of Epidemiology, University of California, Irvine, CA, USA.
Neurobiol Aging. 2021 Oct;106:282-291. doi: 10.1016/j.neurobiolaging.2021.06.021. Epub 2021 Jul 4.
Diffusion imaging studies have observed age-related degradation of white matter that contributes to cognitive deficits separately in younger-old (ages 65-89) and oldest-old (ages 90+) adults. But it remains unclear whether these age effects are magnified in advanced age groups, which may reflect disease-related pathology. Here, we tested whether age-related differences in white matter microstructure followed linear or nonlinear patterns across the entire older adult lifespan (65-98 years), these patterns were influenced by oldest-old adults at increased risk of dementia (cognitive impairment no dementia, CIND), and they explained age effects on episodic memory. Results revealed nonlinear microstructure declines across fiber classes (medial temporal, callosal, association, projection and/or thalamic) that were largest for medial temporal fibers. These patterns remained after excluding oldest-old participants with CIND, indicating that aging of white matter microstructure cannot solely be explained by pathology associated with early cognitive impairment. Moreover, finding that the effect of age on episodic memory was mediated by medial temporal fiber microstructure suggests it is essential for facilitating memory-related neural signals across the older adult lifespan.
扩散成像研究观察到，与年龄相关的白质退化分别导致年轻老年人（65-89 岁）和最老年人（90 岁以上）认知能力下降。但目前尚不清楚这些年龄效应是否在高龄人群中放大，这可能反映了与疾病相关的病理学。在这里，我们测试了白质微观结构的年龄相关性差异是否在整个老年人生存期（65-98 岁）内呈线性或非线性模式，这些模式是否受到最老年人群中认知障碍风险增加的影响（认知障碍但无痴呆，CIND），以及它们是否解释了年龄对情景记忆的影响。结果表明，纤维类别（内侧颞叶、胼胝体、联合、投射和/或丘脑）的微观结构呈非线性下降，内侧颞叶纤维的下降幅度最大。排除患有 CIND 的最老年参与者后，这些模式仍然存在，这表明白质微观结构的老化不能仅用与早期认知障碍相关的病理学来解释。此外，发现年龄对情景记忆的影响是由内侧颞叶纤维微观结构介导的，这表明它对于促进整个老年人生存期与记忆相关的神经信号至关重要。
