静息状态功能磁共振成像观察轻度阿尔茨海默病后扣带回功能连通性的变化

Changes in posterior cingulated cortex functional connectivity of resting-state functional magnetic resonance hnaging in mild Alzheimer＇ s disease

目的 利用静息状态功能磁共振成像（fMRI）研究阿尔茨海默病（AD）早期后扣带回相关的静息脑网络连通性是如何变化的。方法 运用fMRI研究了16例轻度AD患者和16名健康对照者在静息状态后扣带回的功能连通性。与后扣带回有功能连通性的脑区是通过检测低频波动信号的时程相关性获得的。应用通用的SPM2图像统计软件计算组间和组内连通性差异，激活区阈值设置：P〈0.01（校正），像素范围〉5。利用SPM2软件随机效应分析t检验（经校正P〈0．01，t=2，47，像素范围〉5），比较患者组和对照组连通性激活的脑区。结果 与后扣带回有功能连通性减弱的脑区包括前额叶中线区、楔前叶、双侧视皮质、双侧颞下回、左侧海马、右侧丘脑、右侧额叶背外侧区；偏左侧化的连通性增高的脑区包括前额叶中线区、左侧颞下回、左侧基底节区、双侧额叶背外侧区及左侧中央前区。结论 与后扣带回相关的静息状态脑网络连通性减低与AD早期情节记忆损害和高级视觉功能损害有关系，轻度AD保留着功能连接的重塑性以便维持脑功能。静息fMRI是一种探索AD脑功能机制的适宜方法。

Objective To investigate how functional connectivity changes within default-mode network related to posterior cingulated cortex employing resting-state functional MRI （fMRI）. Methods fMRI was compared between 16 mild Alzheimer＇ s disease （AD） patients and 16 normal elder subjects. Regions of functional connectivity to posterior cingulated cortex were gathered by calculating temporal correlations in low frequency fMRI signal fluctuations. SPM2 was applied to calculate significant differences of connectivity between group and within group. Significance threshold was set up at the corrected P 〈 0. 01, pixel extent 〉 5. A random effect two-example t test was performed by SPM2 to achieve significant difference of functional connection between groups （ P 〈 0. 01, corrected, t = 2. 47, pixel extent 〉 5 ）. Results Regions showing disrupted connectivity to posterior cingulated cortex were： ventral medial prefrontal cortex （MPFC）, bilateral visual cortex, infero-temporal cortex （ITC）, and left hippocampus, right thalamus, right dorsal-lateral prefrontal cortex （DLPFC）, and precuneus. There were also regions showing increased connectivity with leftward asymmetry, these regions included： MPFC, left ITC, bilateral DLPFC, left precentral motor cortex and left basal ganglia. Conclusions Impairments of memory and high visual-related functions in AD can be explained by functional disconnection in resting-state. Remoldability is reserved in mild AD to compensate for brain function which is taxed by left hemisphere preferentially. Our findings suggest that resting-state fMRI might be an appropriate approach for evaluating AD brain mechanism.