Objective: Numerous electroencephalography (EEG) studies focus on the alteration of electrical activity in patients with Alzheimer’s Disease (AD), but there are no consistent results especially regarding functional connectivity. We supposed that the weighted Phase Lag Index (w- PLI), as phase-based measures of functional connectivity, may be used as an auxiliary diagnostic method for AD.

Methods: We enrolled 30 patients with AD, 30 patients with Mild Cognitive Impairment (MCI), and 30 Healthy Controls (HC). EEGs were recorded in all participants at baseline during relaxed wakefulness. Following EEG preprocessing, Power Spectral Density (PSD) and wPLI parameters were determined to further analyze whether they were correlated to cognitive scores.

Results: In the patients with AD, the increased PSD in theta band was presented compared with MCI and HC groups, which was associated with disturbances of the directional, computational, and delayed memory capacity. Furthermore, the wPLI revealed a distinctly lower connection strength between frontal and distant areas in the delta band and a higher connection strength of the central and temporo-occipital region in the theta band for AD patients. Moreover,we found a significant negative correlation between theta functional connectivity and cognitive scores.

Conclusion: Increased theta PSD and decreased delta wPLI may be one of the earliest changes in AD and associated with disease severity. The parameter wPLI is a novel measurement of phase synchronization and has potentials in understanding underlying functional connectivity and aiding in the diagnostics of AD.

目的：许多脑电图 (EEG) 研究都集中在阿尔茨海默病 (AD) 患者的电活动改变上，但没有一致的结果，尤其是在功能连接方面。我们假设加权相位滞后指数 (w-PLI) 作为基于相位的功能连通性测量，可用作 AD 的辅助诊断方法。

方法：我们招募了 30 名 AD 患者、30 名轻度认知障碍 (MCI) 患者和 30 名健康对照 (HC)。在放松清醒期间，所有参与者在基线时都记录了脑电图。在 EEG 预处理之后，确定功率谱密度 (PSD) 和 wPLI 参数以进一步分析它们是否与认知评分相关。

结果：与 MCI 和 HC 组相比，AD 患者的 theta 波段 PSD 增加，这与方向、计算和延迟记忆能力的紊乱有关。此外，wPLI 显示，对于 AD 患者，δ 带中额叶和远侧区域之间的连接强度明显较低，而 θ 带中中央和颞枕区域的连接强度更高。此外，我们发现θ功能连接和认知评分之间存在显着的负相关。

结论：增加的 theta PSD 和减少的 delta wPLI 可能是 AD 的最早变化之一，并且与疾病严重程度相关。参数 wPLI 是一种新颖的相位同步测量方法，具有了解潜在功能连接性和帮助诊断 AD 的潜力。