Li Karl, Laird Angela R, Price Larry R, McKay D Reese, Blangero John, Glahn David C, Fox Peter T
Research Imaging Institute, University of Texas Health Science Center San Antonio San Antonio, TX, USA.
Department of Physics, Florida International University Miami, FL, USA.
Front Aging Neurosci. 2016 Jun 14;8:137. doi: 10.3389/fnagi.2016.00137. eCollection 2016.
The default mode network (DMN) is a set of regions that is tonically engaged during the resting state and exhibits task-related deactivation that is readily reproducible across a wide range of paradigms and modalities. The DMN has been implicated in numerous disorders of cognition and, in particular, in disorders exhibiting age-related cognitive decline. Despite these observations, investigations of the DMN in normal aging are scant. Here, we used blood oxygen level dependent (BOLD) functional magnetic resonance imaging (fMRI) acquired during rest to investigate age-related changes in functional connectivity of the DMN in 120 healthy normal volunteers comprising six, 20-subject, decade cohorts (from 20-29 to 70-79). Structural equation modeling (SEM) was used to assess age-related changes in inter-regional connectivity within the DMN. SEM was applied both using a previously published, meta-analytically derived, node-and-edge model, and using exploratory modeling searching for connections that optimized model fit improvement. Although the two models were highly similar (only 3 of 13 paths differed), the sample demonstrated significantly better fit with the exploratory model. For this reason, the exploratory model was used to assess age-related changes across the decade cohorts. Progressive, highly significant changes in path weights were found in 8 (of 13) paths: four rising, and four falling (most changes were significant by the third or fourth decade). In all cases, rising paths and falling paths projected in pairs onto the same nodes, suggesting compensatory increases associated with age-related decreases. This study demonstrates that age-related changes in DMN physiology (inter-regional connectivity) are bidirectional, progressive, of early onset and part of normal aging.
默认模式网络（DMN）是一组在静息状态下持续活跃的脑区，并且在各种范式和模态下都表现出与任务相关的失活，这种失活很容易重复出现。DMN与多种认知障碍有关，尤其是与表现出与年龄相关的认知衰退的疾病有关。尽管有这些观察结果，但对正常衰老过程中DMN的研究却很少。在这里，我们使用静息状态下采集的血氧水平依赖（BOLD）功能磁共振成像（fMRI）来研究120名健康正常志愿者（包括六个由20名受试者组成的十年队列，年龄从20 - 29岁到70 - 79岁）中DMN功能连接的年龄相关变化。结构方程模型（SEM）用于评估DMN内区域间连接的年龄相关变化。SEM既使用了先前发表的、基于元分析得出的节点和边模型，也使用了探索性建模来寻找优化模型拟合改进的连接。尽管这两个模型非常相似（13条路径中只有3条不同），但样本与探索性模型的拟合度明显更好。因此，使用探索性模型来评估十年队列中的年龄相关变化。在13条路径中的8条路径上发现了路径权重的渐进且高度显著的变化：4条上升，4条下降（大多数变化在第三个或第四个十年时显著）。在所有情况下，上升路径和下降路径成对地投射到相同的节点上，表明与年龄相关的减少相关的补偿性增加。这项研究表明，DMN生理学（区域间连接）的年龄相关变化是双向的、渐进的、早发的，并且是正常衰老的一部分。
