Liu Zhenyu, Bai Lijun, Dai Ruwei, Zhong Chongguang, Wang Hu, You Youbo, Wei Wenjuan, Tian Jie
Intelligent Medical Research Center, Institute of Automation, Chinese Academy of Sciences, Beijing, China.
Annu Int Conf IEEE Eng Med Biol Soc. 2012;2012:5454-7. doi: 10.1109/EMBC.2012.6347228.
Mild cognitive impairment (MCI) was recognized as the prodromal stage of Alzheimer's disease (AD). Recent neuroimaging studies have shown that the cognitive and memory decline in AD and MCI patients is coupled with abnormal functions of focal brain regions and disrupted functional connectivity between distinct brain regions, as well as losses of small-world attributes. However, the causal interactions among the spatially isolated but function-related resting state networks (RSNs) are still largely unexplored in MCI patients. In this study, we first identified eight RSNs by independent components analysis (ICA) from resting state functional MRI data of 16 MCI patients and 18 age-matched healthy subjects respectively. Then, we performed a multivariate Granger causality analysis (mGCA) to evaluate the effective connectivity among the RSNs. We found that MCI patients exhibited decreased causal interactions among the RSNs in both intensity and quantity compared with normal controls. Results from mGCA indicated that the causal interactions involving the default mode network (DMN) became weaker in MCI patients, while stronger causal connectivity emerged related to the memory network and executive control network. Our findings suggested that the DMN played a less important role in MCI patients. Increased causal connectivity of the memory network and executive control network may elucidate the dysfunctional and compensatory processes in the brain networks of MCI patients. These preliminary findings may be helpful for further understanding the pathological mechanisms of MCI and provide a new clue to explore the neurophysiological mechanisms of MCI.
轻度认知障碍（MCI）被认为是阿尔茨海默病（AD）的前驱阶段。最近的神经影像学研究表明，AD和MCI患者的认知和记忆衰退与局部脑区功能异常、不同脑区之间功能连接中断以及小世界属性丧失有关。然而，在MCI患者中，空间上孤立但功能相关的静息态网络（RSN）之间的因果相互作用仍 largely未被探索。在本研究中，我们首先通过独立成分分析（ICA）分别从16例MCI患者和18例年龄匹配的健康受试者的静息态功能磁共振成像数据中识别出8个RSN。然后，我们进行了多变量格兰杰因果分析（mGCA）以评估RSN之间的有效连接性。我们发现，与正常对照组相比，MCI患者在RSN之间的因果相互作用在强度和数量上均降低。mGCA结果表明，在MCI患者中，涉及默认模式网络（DMN）的因果相互作用变弱，而与记忆网络和执行控制网络相关的因果连接性增强。我们的研究结果表明，DMN在MCI患者中发挥的作用较小。记忆网络和执行控制网络因果连接性的增加可能阐明了MCI患者脑网络中的功能障碍和代偿过程。这些初步发现可能有助于进一步理解MCI的病理机制，并为探索MCI的神经生理机制提供新线索。
