Aix-Marseille Université, Inserm, Institut de Neurosciences des Systèmes UMR_S 1106 , 13385, Marseille, France ; Aix-Marseille Université, CNRS, Institut des Sciences du Mouvement UMR 7287 , 13288, Marseille, France.
Aix-Marseille Université, Inserm, Institut de Neurosciences des Systèmes UMR_S 1106 , 13385, Marseille, France ; Max Planck Institute for Human Development, Center for Lifespan Psychology , 14195, Berlin, Germany.
eNeuro. 2015 Jun 3;2(3). doi: 10.1523/ENEURO.0067-14.2015. eCollection 2015 May-Jun.
The present work focused on the study of fluctuations of cortical activity across time scales in young and older healthy adults. The main objective was to offer a comprehensive characterization of the changes of brain (cortical) signal variability during aging, and to make the link with known underlying structural, neurophysiological, and functional modifications, as well as aging theories. We analyzed electroencephalogram (EEG) data of young and elderly adults, which were collected at resting state and during an auditory oddball task. We used a wide battery of metrics that typically are separately applied in the literature, and we compared them with more specific ones that address their limits. Our procedure aimed to overcome some of the methodological limitations of earlier studies and verify whether previous findings can be reproduced and extended to different experimental conditions. In both rest and task conditions, our results mainly revealed that EEG signals presented systematic age-related changes that were time-scale-dependent with regard to the structure of fluctuations (complexity) but not with regard to their magnitude. Namely, compared with young adults, the cortical fluctuations of the elderly were more complex at shorter time scales, but less complex at longer scales, although always showing a lower variance. Additionally, the elderly showed signs of spatial, as well as between, experimental conditions dedifferentiation. By integrating these so far isolated findings across time scales, metrics, and conditions, the present study offers an overview of age-related changes in the fluctuation electrocortical activity while making the link with underlying brain dynamics.
本研究主要关注年轻和老年健康成年人皮质活动随时间尺度波动的研究。主要目的是全面描述大脑（皮质）信号随年龄变化的可变性，并将其与已知的潜在结构、神经生理和功能变化以及衰老理论联系起来。我们分析了静息状态和听觉Oddball 任务期间年轻和老年人的脑电图 (EEG) 数据。我们使用了广泛的指标，这些指标通常在文献中分别应用，并将它们与更具体的指标进行了比较，以解决它们的局限性。我们的程序旨在克服早期研究中的一些方法学限制，并验证以前的发现是否可以重现并扩展到不同的实验条件。在休息和任务条件下，我们的结果主要表明，与年轻人相比，老年人的 EEG 信号呈现出系统的年龄相关变化，这些变化与波动的结构（复杂性）有关，但与波动的幅度无关。也就是说，与年轻人相比，老年人的皮质波动在较短的时间尺度上更为复杂，但在较长的时间尺度上则不那么复杂，尽管始终显示出较低的方差。此外，老年人表现出空间和实验条件去分化的迹象。通过将这些迄今为止在时间尺度、指标和条件上孤立的发现整合在一起，本研究概述了皮质电活动波动随年龄的变化，并与潜在的大脑动力学联系起来。
