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Quantitative measure of complexity of EEG signal dynamics

100%

Klonowski W., Jernajczyk W., Niedzielska K., Rydz A., Stepien R.

Acta Neurobiologiae Experimentalis

1999

vol. 59

issue 4

315-321

Since electroencephalographic (EEG) signal may be considered chaotic, Nonlinear Dynamics and Deterministic Chaos Theory may supply effective quantitative descriptors of EEG dynamics and of underlying chaos in the brain. We have used Karhunen-Loeve decomposition of the covariance matrix of the EEG signal to analyse EEG signals of 4 healthy subjects, under drug-free condition and under the influence of Diazepam. We found that what we call KL-complexity of the signal differs profoundly for the signals registered in different EEG channels, from about 5-8 for signals in frontal channels up to 40 and more in occipital ones. But no consistency in the influence of Diazepam administration on KL-complexity is observed. We also estimated the embedding dimension of the EEG signals of the same subjects, which turned to be between 7 and 11, so endorsing the presumption about existence of low-dimensional chaotic attractor. We are sure that nonlinear time series analysis can be used to investigate the dynamics underlying the generation of EEG signal. This approach does not seem practical yet, but deserves further study.

Zopiclone versus Diazepam effects on EEG power maps in healthy volunteers

75%

Yamadera H., Kato M., Tsukahara Y., Bredeis D., Okuma T.

Acta Neurobiologiae Experimentalis

1997

vol. 57

issue 2

151-155

EEG effects of zopiclone (7.5 mg), a cyclopyrrolone derivative with hypnotic action, were compared with effects of diazepam (10 mg). Multichannel EEG recordings, double blind crossover trials with placebo, and oral single doses were used in healthy volunteers. Vigilance controlled EEG before and after zopiclone (and placebo), and before and after diazepam (and placebo) were analyzed into FFT power spectra. Effects were assessed as placebo referred pre post medication power differences in four frequency bands. Overall statistics showed significant ) global differences between medication effects in the delta frequency band (0.5 3.5 Hz). After zopiclone, fronto central delta increased bilaterally, whereas after diazepam delta decreased over centro parietal to right temporo occipital regions. These spatially different brain electric effects show that different neuronal populations must have become active in response to zopiclone and diazepam.

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2 Acta Neurobiologiae Experimentalis

1 1999

1 1997

1 Bredeis D.

1 Jernajczyk W.

1 Kato M.

1 Klonowski W.

1 Niedzielska K.

1 Okuma T.

1 Rydz A.

1 Stepien R.

1 Tsukahara Y.

1 Yamadera H.

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Quantitative measure of complexity of EEG signal dynamics

Zopiclone versus Diazepam effects on EEG power maps in healthy volunteers