Non-linear time series analysis of intracranial EEG recordings in patients with epilepsy

Journal/Book: Int J Psychophysiol. 1999; 34: PO Box 211, 1000 AE Amsterdam, Netherlands. Elsevier Science Bv. 45-52.

Abstract: Deterministic chaos offers a striking explanation for apparently irregular behavior, a characteristic feature of brain electrical activity. The framework of the theory of non-linear dynamics provides new concepts and powerful algorithms to analyze such time series. However, different influencing factors render the use of non-linear measures in a strict sense problematic. Nevertheless, if interpreted with care, particularly the correlation dimension or the Lyapunov-exponents provide a means to reliably characterize different states of normal and pathological brain function. This overview summarizes recent findings applying this concept in the field of epileptology that promise to be important for clinical practice. Non-linear measures extracted from the intra-cranially recorded EEG allow (a) localization of epileptogenic areas in different cerebral regions even during seizure-free intervals, (b) investigation of the influence of anticonvulsive drugs and (c) detection of features predictive of imminent seizure activity. Moreover, particularly the dimensional complexity proves a valuable parameter reflecting spatially distributed neuronal activity during verbal learning and memory processes. Specific changes in time of this non-linear measure allow the prediction of memory performance and, in addition, represent an estimate of the recruitment potency in the anterior mesial temporal lobes. Thus, the application of non-linear time series analysis to brain electrical activity offers new information about the dynamics of the underlying neuronal networks.

Note: Article Lehnertz K, Univ Bonn, Clin Epileptol, Sigmund Freud Str 25, D-53105 Bonn, GERMANY

Keyword(s): EEG; non-linear time series analysis; correlation dimension; neuronal complexity loss; memory; epilepsy; TEMPORAL-LOBE EPILEPSY; NEURONAL COMPLEXITY LOSS; PRIMARY EPILEPTOGENIC AREA; BRAIN ELECTRICAL-ACTIVITY; NONLINEAR DYNAMICS; SEIZURES; CHAOS; ELECTROENCEPHALOGRAMS; REPLICATION; SPIKING

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Non-linear time series analysis of intracranial EEG recordings in patients with epilepsy - an overview