21 April 2016 Evaluation of nonlinear properties of epileptic activity using largest Lyapunov exponent
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Absence seizures are known to be highly non-linear large amplitude oscillations with a well pronounced main time scale. Whilst the appearance of the main frequency is usually considered as a transition from noisy complex dynamics of baseline EEG to more regular absence activity, the dynamical properties of this type of epileptiformic activity in genetic absence models was not studied precisely.

Here, the estimation of the largest Lyapunov exponent from intracranial EEGs of 10 WAG/Rij rats (genetic model of absence epilepsy) was performed. Fragments of 10 seizures and 10 episodes of on-going EEG each of 4 s length were used for each animal, 3 cortical and 2 thalamic channels were analysed. The method adapted for short noisy data was implemented. The positive values of the largest Lyapunov exponent were found as for baseline as for spike wave discharges (SWDs), with values for SWDs being significantly less than for on-going activity.

Current findings may indicate that SWD is a chaotic process with a well pronounced main timescale rather than a periodic regime. Also, the absence activity was shown to be less chaotic than the baseline one.
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Tatiana M. Medvedeva, Tatiana M. Medvedeva, Annika Lüttjohann, Annika Lüttjohann, Gilles van Luijtelaar, Gilles van Luijtelaar, Ilya V. Sysoev, Ilya V. Sysoev, "Evaluation of nonlinear properties of epileptic activity using largest Lyapunov exponent", Proc. SPIE 9917, Saratov Fall Meeting 2015: Third International Symposium on Optics and Biophotonics and Seventh Finnish-Russian Photonics and Laser Symposium (PALS), 991724 (21 April 2016); doi: 10.1117/12.2229817; https://doi.org/10.1117/12.2229817

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