Center on Aging Psychology, Key Laboratory of Mental Health, Institute of Psychology, Chinese Academy of Sciences, Beijing, China ; Magnetic Resonance Imaging Research Center, Institute of Psychology, Chinese Academy of Sciences, Beijing, China.
PLoS One. 2013 Dec 6;8(12):e82104. doi: 10.1371/journal.pone.0082104. eCollection 2013.
Alzheimer's disease (AD) is associated with abnormal functioning of the default mode network (DMN). Functional connectivity (FC) changes to the DMN have been found in patients with amnestic mild cognitive impairment (aMCI), which is the prodromal stage of AD. However, whether or not aMCI also alters the effective connectivity (EC) of the DMN remains unknown. We employed a combined group independent component analysis (ICA) and Bayesian network (BN) learning approach to resting-state functional MRI (fMRI) data from 17 aMCI patients and 17 controls, in order to establish the EC pattern of DMN, and to evaluate changes occurring in aMCI. BN analysis demonstrated heterogeneous regional convergence degree across DMN regions, which were organized into two closely interacting subsystems. Compared to controls, the aMCI group showed altered directed connectivity weights between DMN regions in the fronto-parietal, temporo-frontal, and temporo-parietal pathways. The aMCI group also exhibited altered regional convergence degree in the right inferior parietal lobule. Moreover, we found EC changes in DMN regions in aMCI were correlated with regional FC levels, and the connectivity metrics were associated with patients' cognitive performance. This study provides novel sights into our understanding of the functional architecture of the DMN and adds to a growing body of work demonstrating the importance of the DMN as a mechanism of aMCI.
阿尔茨海默病（AD）与默认模式网络（DMN）的异常功能有关。在遗忘型轻度认知障碍（aMCI）患者中发现了 DMN 的功能连接（FC）变化，aMCI 是 AD 的前驱阶段。然而，aMCI 是否也改变了 DMN 的有效连接（EC）尚不清楚。我们采用了联合组独立成分分析（ICA）和贝叶斯网络（BN）学习方法，对 17 名 aMCI 患者和 17 名对照的静息状态功能磁共振成像（fMRI）数据进行分析，以建立 DMN 的 EC 模式，并评估 aMCI 中发生的变化。BN 分析表明，DMN 区域之间的区域收敛程度存在异质性，这些区域被组织成两个紧密相互作用的子系统。与对照组相比，aMCI 组在额顶、颞额和颞顶通路中 DMN 区域之间的定向连接权重发生了改变。aMCI 组还表现出右侧下顶叶区域的区域收敛程度发生了改变。此外，我们发现 aMCI 患者 DMN 区域的 EC 变化与局部 FC 水平相关，连接指标与患者的认知表现相关。本研究为我们理解 DMN 的功能结构提供了新的视角，并为越来越多的证明 DMN 作为 aMCI 机制的重要性的工作提供了补充。
