Wang Bin, Niu Yan, Miao Liwen, Cao Rui, Yan Pengfei, Guo Hao, Li Dandan, Guo Yuxiang, Yan Tianyi, Wu Jinglong, Xiang Jie, Zhang Hui
College of Computer Science and Technology, Taiyuan University of Technology, Taiyuan, China.
Department of Radiology, First Hospital of Shanxi Medical University, Taiyuan, China.
Front Aging Neurosci. 2017 Nov 20;9:378. doi: 10.3389/fnagi.2017.00378. eCollection 2017.
Alzheimer's disease (AD) is a frequently observed, irreversible brain function disorder among elderly individuals. Resting-state functional magnetic resonance imaging (rs-fMRI) has been introduced as an alternative approach to assessing brain functional abnormalities in AD patients. However, alterations in the brain rs-fMRI signal complexities in mild cognitive impairment (MCI) and AD patients remain unclear. Here, we described the novel application of permutation entropy (PE) to investigate the abnormal complexity of rs-fMRI signals in MCI and AD patients. The rs-fMRI signals of 30 normal controls (NCs), 33 early MCI (EMCI), 32 late MCI (LMCI), and 29 AD patients were obtained from the Alzheimer's disease Neuroimaging Initiative (ADNI) database. After preprocessing, whole-brain entropy maps of the four groups were extracted and subjected to Gaussian smoothing. We performed a one-way analysis of variance (ANOVA) on the brain entropy maps of the four groups. The results after adjusting for age and sex differences together revealed that the patients with AD exhibited lower complexity than did the MCI and NC controls. We found five clusters that exhibited significant differences and were distributed primarily in the occipital, frontal, and temporal lobes. The average PE of the five clusters exhibited a decreasing trend from MCI to AD. The AD group exhibited the least complexity. Additionally, the average PE of the five clusters was significantly positively correlated with the Mini-Mental State Examination (MMSE) scores and significantly negatively correlated with Functional Assessment Questionnaire (FAQ) scores and global Clinical Dementia Rating (CDR) scores in the patient groups. Significant correlations were also found between the PE and regional homogeneity (ReHo) in the patient groups. These results indicated that declines in PE might be related to changes in regional functional homogeneity in AD. These findings suggested that complexity analyses using PE in rs-fMRI signals can provide important information about the fMRI characteristics of cognitive impairments in MCI and AD.
阿尔茨海默病（AD）是老年人群中常见的一种不可逆的脑功能障碍。静息态功能磁共振成像（rs-fMRI）已被引入作为评估AD患者脑功能异常的一种替代方法。然而，轻度认知障碍（MCI）和AD患者脑rs-fMRI信号复杂性的改变仍不清楚。在此，我们描述了排列熵（PE）在研究MCI和AD患者rs-fMRI信号异常复杂性方面的新应用。从阿尔茨海默病神经影像倡议（ADNI）数据库中获取了30名正常对照（NC）、33名早期MCI（EMCI）、32名晚期MCI（LMCI）和29名AD患者的rs-fMRI信号。预处理后，提取四组的全脑熵图并进行高斯平滑。我们对四组的脑熵图进行了单因素方差分析（ANOVA）。在综合调整年龄和性别差异后的结果显示，AD患者的复杂性低于MCI和NC对照组。我们发现了五个表现出显著差异的簇，主要分布在枕叶、额叶和颞叶。五个簇的平均PE从MCI到AD呈下降趋势。AD组的复杂性最低。此外，在患者组中，五个簇的平均PE与简易精神状态检查表（MMSE）评分显著正相关，与功能评估问卷（FAQ）评分和整体临床痴呆评定量表（CDR）评分显著负相关。在患者组中还发现PE与局部一致性（ReHo）之间存在显著相关性。这些结果表明，PE的下降可能与AD中局部功能一致性的变化有关。这些发现提示，在rs-fMRI信号中使用PE进行复杂性分析可以为MCI和AD认知障碍的功能磁共振成像特征提供重要信息。
