OBJECTIVE To analyse magnetoencephalogram (MEG) signals with Lempel-Ziv Complexity (LZC) to identify the regions of the brain showing changes related to cognitive decline and Alzheimeŕs Disease (AD). METHODS LZC was used to study MEG signals in the source space from 99 participants (36 male, 63 female, average age: 71.82 ± 4.06) in three groups (33 subjects per group): healthy (control) older adults, older adults with subjective cognitive decline (SCD), and adults with mild cognitive impairment (MCI). Analyses were performed in broadband (2-45 Hz) and in classic narrow bands (theta (4-8 Hz), alpha (8-12 Hz), low beta (12-20 Hz), high beta (20-30 Hz), and, gamma (30-45 Hz)). RESULTS LZC was significantly lower in subjects with MCI than in those with SCD. Moreover, subjects with MCI had significantly lower MEG complexity than controls and SCD subjects in the beta frequency band. Lower complexity was correlated with smaller hippocampal volumes. CONCLUSIONS Brain complexity - measured with LZC - decreases in MCI patients when compared to SCD and healthy controls. This decrease is associated with a decrease in hippocampal volume, a key feature in AD progression. SIGNIFICANCE This is the first study to date characterising the changes of brain activity complexity showing the specific spatial pattern of the alterations as well as the morphological correlations throughout preclinical stages of AD.

中文翻译：

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临床前阿尔茨海默病的复杂性变化：主观认知衰退和轻度认知障碍的 MEG 研究

目的 使用 Lempel-Ziv 复杂性 (LZC) 分析脑磁图 (MEG) 信号，以识别显示与认知能力下降和阿尔茨海默病 (AD) 相关的变化的大脑区域。方法 LZC 用于研究来自 99 名参与者（36 名男性，63 名女性，平均年龄：71.82 ± 4.06）的源空间中的 MEG 信号，分为三组（每组 33 名受试者）：健康（对照）老年人、具有主观认知能力下降 (SCD) 和患有轻度认知障碍 (MCI) 的成年人。在宽带 (2-45 Hz) 和经典窄带 (theta (4-8 Hz)、alpha (8-12 Hz)、低 beta (12-20 Hz)、高 beta (20-30 Hz) 中进行分析) , 和, 伽玛 (30-45 Hz))。结果 MCI 受试者的 LZC 显着低于 SCD 受试者。而且，MCI 受试者的 MEG 复杂性显着低于 beta 频带中的对照组和 SCD 受试者。较低的复杂性与较小的海马体积相关。结论与 SCD 和健康对照相比，MCI 患者的大脑复杂性 - 用 LZC 测量 - 降低。这种减少与海马体积的减少有关，这是 AD 进展的一个关键特征。意义这是迄今为止第一项表征大脑活动复杂性变化的研究，显示了 AD 临床前阶段的特定空间模式以及形态学相关性。这种减少与海马体积的减少有关，这是 AD 进展的一个关键特征。意义这是迄今为止第一项表征大脑活动复杂性变化的研究，显示了 AD 临床前阶段的特定空间模式以及形态学相关性。这种减少与海马体积的减少有关，这是 AD 进展的一个关键特征。意义这是迄今为止第一项表征大脑活动复杂性变化的研究，显示了 AD 临床前阶段的特定空间模式以及形态学相关性。