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Article

Complexity Changes in Brain Activity in Healthy Ageing: A Permutation Lempel-Ziv Complexity Study of Magnetoencephalograms

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Centre for Biomedical Engineering, Department of Mechanical Engineering Sciences, Faculty of Engineering and Physical Sciences, University of Surrey, Guildford GU2 7XH, UK
2
Laboratorio UPM-UCM de Neurociencia Cognitiva y Computacional, Universidad Complutense de Madrid-Universidad Politécnica de Madrid. Departamento de Medicina Legal, Psiquiatría y Patología, Universidad Complutense de Madrid, Madrid 28040, Spain
*
Author to whom correspondence should be addressed.
Entropy 2018, 20(7), 506; https://doi.org/10.3390/e20070506
Received: 1 June 2018 / Revised: 26 June 2018 / Accepted: 28 June 2018 / Published: 3 July 2018
(This article belongs to the Special Issue Permutation Entropy & Its Interdisciplinary Applications)
Maturation and ageing, which can be characterised by the dynamic changes in brain morphology, can have an impact on the physiology of the brain. As such, it is possible that these changes can have an impact on the magnetic activity of the brain recorded using magnetoencephalography. In this study changes in the resting state brain (magnetic) activity due to healthy ageing were investigated by estimating the complexity of magnetoencephalogram (MEG) signals. The main aim of this study was to identify if the complexity of background MEG signals changed significantly across the human lifespan for both males and females. A sample of 177 healthy participants (79 males and 98 females aged between 21 and 80 and grouped into 3 categories i.e., early-, mid- and late-adulthood) was used in this investigation. This investigation also extended to evaluating if complexity values remained relatively stable during the 5 min recording. Complexity was estimated using permutation Lempel-Ziv complexity, a recently introduced complexity metric, with a motif length of 5 and a lag of 1. Effects of age and gender were investigated in the MEG channels over 5 brain regions, i.e., anterior, central, left lateral, posterior, and, right lateral, with highest complexity values observed in the signals recorded by the channels over the anterior and central regions of the brain. Results showed that while changes due to age had a significant effect on the complexity of the MEG signals recorded over 5 brain regions, gender did not have a significant effect on complexity values in all age groups investigated. Moreover, although some changes in complexity were observed between the different minutes of recording, due to the small magnitude of the changes it was concluded that practical significance might outweigh statistical significance in this instance. The results from this study can contribute to form a fingerprint of the characteristics of healthy ageing in MEGs that could be useful when investigating changes to the resting state activity due to pathology. View Full-Text
Keywords: magnetoencephalography; permutation Lempel-Ziv complexity; life span; healthy ageing magnetoencephalography; permutation Lempel-Ziv complexity; life span; healthy ageing
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MDPI and ACS Style

Shumbayawonda, E.; Tosun, P.D.; Fernández, A.; Hughes, M.P.; Abásolo, D. Complexity Changes in Brain Activity in Healthy Ageing: A Permutation Lempel-Ziv Complexity Study of Magnetoencephalograms. Entropy 2018, 20, 506. https://doi.org/10.3390/e20070506

AMA Style

Shumbayawonda E, Tosun PD, Fernández A, Hughes MP, Abásolo D. Complexity Changes in Brain Activity in Healthy Ageing: A Permutation Lempel-Ziv Complexity Study of Magnetoencephalograms. Entropy. 2018; 20(7):506. https://doi.org/10.3390/e20070506

Chicago/Turabian Style

Shumbayawonda, Elizabeth, Pinar D. Tosun, Alberto Fernández, Michael P. Hughes, and Daniel Abásolo. 2018. "Complexity Changes in Brain Activity in Healthy Ageing: A Permutation Lempel-Ziv Complexity Study of Magnetoencephalograms" Entropy 20, no. 7: 506. https://doi.org/10.3390/e20070506

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