Entropy analysis of the EEG background activity in Alzheimer's disease patients

Abstract

Alzheimer's disease (AD) is the most common neurodegenerative disorder. Although a definite diagnosis is only possible by necropsy, a differential diagnosis with other types of dementia and with major depression should be attempted. The aim of this study was to analyse the EEG background activity of AD patients to test the hypothesis that the regularity of the AD patients' EEG is higher than that of age-matched controls. We recorded the EEG from 19 scalp electrodes in 11 AD patients and 11 age-matched controls. Two different methods were used to estimate the regularity of the EEG background activity: Spectral entropy (SpecEn) and Sample entropy (SampEn). We did not find significant differences between AD patients and control subjects' EEGs with SpecEn. On the other hand, AD patients had significantly lower SampEn values than control subjects (p < 0.01) at electrodes P3, P4, O1 and O2. Our results show an increase of EEG regularity in AD patients. These findings suggest that non-linear analysis of the EEG with SampEn could yield essential information and may contribute to increase the insight into brain dysfunction in AD in ways which are not possible with more classical and conventional statistical methods.

Analysis of MEG Background Activity in Alzheimer’s Disease Using Nonlinear Methods and ANFIS

“…These results are in agreement with previous research works that have applied non-linear methods to estimate the regularity of the AD patients' brain activity. 1,2,12,17 ApEn values were significantly lower in the EEG of AD patients at electrodes P3 and P4, 1 whereas statistically significant differences were found at P3, P4, O1 and O2 using SampEn. 2 Our results also showed that AD patients have lower LZC values than controls.…”

“…Hence, other non-linear methods are necessary to study brain recordings. For instance, Abásolo et al 2 found significant differences in some EEG channels with sample entropy (SampEn), concluding that the EEG background activity is more regular in AD patients than in control subjects. EEG/MEG studies demonstrated that AD patients have significantly lower Lempel-Ziv complexity (LZC) values than elderly control subjects.…”

“…These values follow the aforementioned guidelines and have been used in a previous AD study. 2 This measure has already been used to study some biological signals, such as heart rate time series 27 and EEG data. 2 Given a one dimensional time series X = x(1), x(2),..., x(N), the algorithm to compute the SampEn can be described as: 35…”

Approximate entropy and auto mutual information analysis of the electroencephalogram in Alzheimer’s disease patients

“…We have previously analysed the same EEG dataset with other non-linear techniques, such as sample entropy (SampEn) [2], Lempel-Ziv (LZ) complexity [3] or multiscale entropy (MSE) [13].…”

A statistical framework for neuroimaging data analysis based on mutual information estimated via a gaussian copula

“…Entropy alone can form a useful measure of the complexity of a signal [Abásolo et al, 2006; Inouye et al, 1991; Overath et al, 2007]. However, here we are interested primarily in its relation to MI, which quantifies the relationship between two variables (for example an external stimulus and a recorded signal) in terms of differences in entropies.…”