中文摘要：

目的采用静息态功能磁共~（fMRD技术，探讨轻度阿尔茨海默病（AD）患者的脑默认活动网络（DMN）是否存在异常及其可能的神经机制。方法以复旦大学附属华山医院和同济大学附属同济医院神经内科门诊自2009年1月至2010年6月收治的24名轻度AD患者和同期上海社区中整群抽样选择的25名正常老年人为研究对象，对其进行简易智能状态（MMSE）、Mattis痴呆评定量表（DRS）检查和静息态脑功能成像。利用低频振幅（ALFF）算法对全脑静息态数据进行对比分析，观察AD患者相对于正常老年人ALFF有显著差异的区域。结果行为学结果显示：轻度AD患者相对对照组成员记忆功能存在明显损害。静息态fMRI结果显示：与对照组比较，AD患者中与记忆密切相关的后扣带回、前额叶中内侧腹侧、前额叶中内侧背侧等脑区ALFF明显减弱。结论AD患者静息态脑DMN中与记忆密切相关的脑区节点活动强度减弱，DMN异常在其早期记忆损害的病理机制中起着非常重要的作用。

英文摘要：

Objective To explore the activity of brain default mode network （DIVIN） in patients with mild Alzheimer＇s disease （AD） by resting state functional magnetic resonance imaging （fMRI） and investigate its possible neural mechanism. Methods Twenty-four patients with mild AD, admitted to our hospital from January 2009 to June 2010, and 25 normal controls （NCs） were chosen in this study. All subjects were examined by Mini Mental State Examination （MMSE）, Mattis Dementia Rating Scale （DRS） and fMRI. Resting-state whole brain data were analyzed by amplitude of low frequency fluctuation （ALFF） with two-sample t test and the brain regions in mild AD patients having significantly different ALFF comparing to NCs were observed. Results As compared with that in NCs, the memory function in mild AD patients was seriously impaired （P〈0.05）. As compared with NCs, mild AD patients showed significantly decreased ALFF in the posterior cingnlate cortex, ventral medial prefrontal cortex and dorsal medial prefrontal cortex, which were closely relevant to the memory （P〈0.05）. Conclusion AD patients show significantly decreased active intensity of some DMN nodes that relate to memory in resting state; DMN abnormalities play an important role in early memory impairment of AD patients.