The aim of this study was to characterize the EEG alterations in inter-band interactions along the Alzheimer's disease (AD) continuum. For this purpose, EEG background activity from 51 healthy control subjects, 51 mild cognitive impairment patients, 50 mild AD patients, 50 moderate AD patients, and 50 severe AD patients was analyzed by means of bispectrum. Three inter-band features were extracted from bispectrum matrices: bispectral relative power (BispRP), cubic bispectral entropy (BispEn), and bispectral median frequency (BispMF). BispRP results showed an increase of delta and theta interactions with other frequency bands and the opposite behavior for alpha, beta-1, and beta-2. Delta and theta interactions, along with the rest of the spectrum, also experimented a decrease of BispEn with disease progression, suggesting these bands interact with a reduced variety of components in advanced stages of dementia. Finally, BispMF showed a consistent reduction along the AD continuum in all bands, which is reflective of an interaction of the global spectrum with lower frequency bands as the disease develops. Our results indicate a progressive decrease in inter-band interactions with the severity of the disease, especially those involving high frequency components. Since inter-band coupling oscillations are related to complex and multi-scaled brain processes, these alterations likely reflect the neurodegeneration associated with the AD continuum.

中文翻译：

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脑电图背景活动的带间双谱分析来表征阿尔茨海默氏病连续体


本研究的目的是描述阿尔茨海默病 (AD) 连续体中带间相互作用的脑电图变化。为此，通过双谱分析了 51 名健康对照受试者、51 名轻度认知障碍患者、50 名轻度 AD 患者、50 名中度 AD 患者和 50 名重度 AD 患者的脑电图背景活动。从双谱矩阵中提取了三个带间特征：双谱相对功率（BispRP）、立方双谱熵（BispEn）和双谱中频（BispMF）。 BispRP 结果显示 delta 和 theta 与其他频段的相互作用有所增加，而 alpha、beta-1 和 beta-2 的行为则相反。 Delta 和 theta 相互作用，以及谱的其余部分，也实验了 BispEn 随着疾病进展而减少，表明这些谱带与痴呆晚期阶段的成分种类减少相互作用。最后，BispMF 在所有频段中都显示出沿着 AD 连续谱的一致减少，这反映了随着疾病的发展，全局频谱与较低频段的相互作用。我们的结果表明，带间相互作用随着疾病的严重程度而逐渐减少，特别是那些涉及高频成分的相互作用。由于带间耦合振荡与复杂和多尺度的大脑过程有关，这些变化可能反映了与 AD 连续体相关的神经变性。