Weiler Marina, Teixeira Camila Vieira Ligo, Nogueira Mateus Henrique, de Campos Brunno Machado, Damasceno Benito Pereira, Cendes Fernando, Balthazar Marcio Luiz Figueredo
1 Laboratory of Neuroimaging, University of Campinas , Campinas, Brazil .
Brain Connect. 2014 Oct;4(8):567-74. doi: 10.1089/brain.2014.0234. Epub 2014 Sep 19.
There is evidence that the default mode network (DMN) functional connectivity is impaired in Alzheimer's disease (AD) and few studies also reported a decrease in DMN intrinsic activity, measured by the amplitude of low-frequency fluctuations (ALFFs). In this study, we analyzed the relationship between DMN intrinsic activity and functional connectivity, as well as their possible implications on cognition in patients with mild AD and amnestic mild cognitive impairment (aMCI) and healthy controls. In addition, we evaluated the differences both in connectivity and ALFF values between these groups. We recruited 29 controls, 20 aMCI, and 32 mild AD patients. To identify the DMN, functional connectivity was calculated by placing a seed in the posterior cingulate cortex (PCC). Within the DMN mask obtained, we calculated regional average ALFFs. Compared with controls, aMCI patients showed decreased ALFFs in the temporal region; compared with AD, aMCI showed higher values in the PCC but lower in the temporal area. The mild AD group had lower ALFFs in the PCC compared with controls. There was no difference between the connectivity in the aMCI group compared with the other groups, but AD patients showed decreased connectivity in the frontal, parietal, and PCC. Also, PCC ALFFs correlated to functional connectivity in nearly all subregions. Cognitive tests correlated to connectivity values but not to ALFFs. In conclusion, we found that DMN connectivity and ALFFs are correlated in these groups. Decreased PCC ALFFs disrupt the DMN functional organization, leading to cognitive problems in the AD spectrum.
有证据表明，阿尔茨海默病（AD）患者的默认模式网络（DMN）功能连接受损，少数研究还报告称，通过低频波动幅度（ALFF）测量的DMN内在活动有所下降。在本研究中，我们分析了轻度AD患者、遗忘型轻度认知障碍（aMCI）患者和健康对照者中DMN内在活动与功能连接之间的关系，以及它们对认知的可能影响。此外，我们评估了这些组在连接性和ALFF值方面的差异。我们招募了29名对照者、20名aMCI患者和32名轻度AD患者。为了识别DMN，通过在后扣带回皮质（PCC）放置一个种子点来计算功能连接。在获得的DMN掩码内，我们计算了区域平均ALFF。与对照者相比，aMCI患者颞叶区域的ALFF降低；与AD患者相比，aMCI患者PCC区域的ALFF值较高，但颞叶区域较低。与对照者相比，轻度AD组PCC区域的ALFF较低。aMCI组与其他组相比，连接性没有差异，但AD患者额叶、顶叶和PCC区域的连接性降低。此外，几乎所有子区域的PCC ALFF与功能连接均相关。认知测试与连接性值相关，但与ALFF无关。总之，我们发现这些组中DMN连接性与ALFF相关。PCC区域ALFF降低会破坏DMN功能组织，导致AD谱系中的认知问题。
