TY - JOUR T1 - Brain Dynamics of Aging: Multiscale Variability of EEG Signals at Rest and during an Auditory Oddball Task JF - eneuro JO - eneuro DO - 10.1523/ENEURO.0067-14.2015 SP - ENEURO.0067-14.2015 AU - Rita Sleimen-Malkoun AU - Dionysios Perdikis AU - Viktor Müller AU - Jean-Luc Blanc AU - Raoul Huys AU - Jean-Jacques Temprado AU - Viktor K Jirsa Y1 - 2015/05/11 UR - http://www.eneuro.org/content/early/2015/05/11/ENEURO.0067-14.2015.abstract N2 - 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) signals variability during aging and make the link with known underlying structural, neurophysiological and functional modifications, as well as aging theories. We analyzed EEG data of young and elderly adults, which were collected at resting state and during an auditory odd-ball task. We used a wide battery of metrics that typically are separately applied in the literature, and we compared them to 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 to young adults, the cortical fluctuations of the elderly were more complex at shorter time-scales, but less complex at longer scales, while 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 fluctuations electrocortical activity while making the link with underlying brain dynamics. Significance Statement: Recently, the study of brain signals fluctuations is widely put forward as a promising entry point to characterize brain dynamics in health and disease. While interesting results have been reported regarding how variability of brain activations can serve as an indicator of performance and adaptability in elderly, many uncertainties and controversies remain with regard to the comparability, reproducibility and generality of the described findings, as well as the ensuing interpretations. Following a systematic investigation of these issues by using a large set of metrics and different experimental conditions, our results draw an overview of age-related changes of the magnitude and structure of brain fluctuations, which integrate well with known structural and functional alterations as well as the main aging theories. ER -