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Entropy 2015, 17(2), 560-579; doi:10.3390/e17020560

Symbolic Entropy of the Amplitude rather than the Instantaneous Frequency of EEG Varies in Dementia

Graduate Institute of Biomedical Electronics and Bioinformatics, National Taiwan University, Taipei 10617, Taiwan
Department of Geriatrics, Tainan Hospital, Ministry of Health and Welfare, Taiwan. No. 125, Jhongshan Road, Tainan 70043, Taiwan
Research Center for Adaptive Data Analysis, National Central University, Jongli 32001, Taiwan
Graduate Institute of Communication Engineering, National Taiwan University, Taipei 10617, Taiwan
These authors contributed equally to this work.
Author to whom correspondence should be addressed.
Received: 17 October 2014 / Accepted: 26 January 2015 / Published: 29 January 2015
(This article belongs to the Special Issue Entropy in Human Brain Networks)
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The dynamics of human electroencephalography (EEG) have been proved to be related to cognitive activities. This study separately assessed the two EEG components, amplitude and rhythm, aiming to capture their individual contributions to cognitive functions. We extracted the local peaks of EEGs under rest or photic stimulation and calculated the symbolic dynamics of their voltages (amplitude) and interpeak intervals (instantaneous frequency), individually. The sample consisted of 89 geriatric outpatients in three patient groups: 38 fresh cases of vascular dementia (VD), 22 fresh cases of Alzheimer’s disease (AD) and 29 controls. Both sample entropy and number of forbidden words revealed significantly less regular symbolic dynamics in the whole EEG tracings of the VD than the AD and control groups. We found consistent results between groups with the symbolic dynamics in the local-peak voltage sequence rather than the interpeak interval sequence. Photic stimulation amplified the differences between groups. These results suggest that the EEG dynamics which relates to either cognitive functions or the underlying pathologies of dementia are embedded within the dynamics of the amount of but not the interval between each synchronized firing of adjacent cerebral neurons. View Full-Text
Keywords: symbolic dynamics; EEG amplitude; photic stimulation; vascular dementia; Alzheimer’s disease symbolic dynamics; EEG amplitude; photic stimulation; vascular dementia; Alzheimer’s disease

This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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Lin, P.-F.; Tsao, J.; Lo, M.-T.; Lin, C.; Chang, Y.-C. Symbolic Entropy of the Amplitude rather than the Instantaneous Frequency of EEG Varies in Dementia. Entropy 2015, 17, 560-579.

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