Mild cognitive impairment (MCI) refers to mild objective cognitive deficits and is associated with the later development of Alzheimer’s disease (AD). However, not all patients with MCI convert to AD. EEG spectral power has shown promise as a marker of progression, but brain oscillations in different frequencies are not isolated entities. Coupling between different frequency bands, so-called cross-frequency coupling (CFC), has been associated with memory function and may further contribute to our understanding of what characterizes patients with MCI who progress to AD. In the current study, we wanted to investigate the changes in gamma/theta CFC in patients with AD and MCI compared to HC and in patients with pMCI compared to patients with sMCI. Furthermore, we wanted to investigate the association with cognitive test scores. EEGs were included at baseline for 15 patients with AD, 25 patients with MCI, and 36 older HC, and the participants were followed for up to 3 years. To investigate CFC, we calculated the modulation index (MI), which has been shown to be less affected by noisy data compared to other techniques. We found that patients with pMCI showed a significantly lower global gamma/theta CFC compared to patients with sMCI. In addition, global gamma/theta CFC was significantly correlated with Addenbrooke’s Cognitive Examination (ACE) score (p-value = 0.030, rho = 0.527). Although not significant, patients with AD and MCI showed a lower gamma/theta CFC compared to HC. These findings suggest that gamma/theta CFC is important for proper cognitive functioning and that a decrease in gamma/theta CFC in patients with MCI may be a sign of progression. Gamma/theta CFC may therefore serve as a progression marker in MCI, but larger studies are needed to validate these findings.

中文翻译：

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脑电图交叉频率耦合作为轻度认知障碍患者疾病进展的标志：一项初步研究

轻度认知障碍 (MCI) 是指轻度客观认知缺陷，与阿尔茨海默病 (AD) 的后期发展有关。然而，并非所有 MCI 患者都会转变为 AD。EEG 频谱功率已显示出作为进展标志物的前景，但不同频率的大脑振荡并不是孤立的实体。不同频段之间的耦合，即所谓的交叉频率耦合 (CFC)，与记忆功能有关，可能进一步有助于我们了解进展为 AD 的 MCI 患者的特征。在目前的研究中，我们想调查 AD 和 MCI 患者与 HC 以及 pMCI 患者与 sMCI 患者相比的 gamma/theta CFC 的变化。此外，我们想调查与认知测试分数的关联。基线时包括 15 名 AD 患者、25 名 MCI 患者和 36 名老年 HC 患者的脑电图，参与者被随访长达 3 年。为了研究 CFC，我们计算了调制指数 (MI)，与其他技术相比，该指数受噪声数据的影响较小。我们发现，与 sMCI 患者相比，pMCI 患者的整体 gamma/theta CFC 显着降低。此外，全局 gamma/theta CFC 与 Addenbrooke 的认知检查 (ACE) 分数显着相关（p 值 = 0.030，rho = 0.527）。尽管不显着，但与 HC 相比，患有 AD 和 MCI 的患者表现出较低的 gamma/theta CFC。这些发现表明 gamma/theta CFC 对正常的认知功能很重要，并且 MCI 患者的 gamma/theta CFC 减少可能是进展的迹象。