Epilepsy Ictal Stage Identification by 0-1 Test of Chaos*

During an epilepsy seizure an Electrocorticosignals (ECoS) may change dramatically from a nearly disordered signal (Inter-Ictal stage) into a highly synchronized signal (Ictal stage), characterized by a high amplitude and low frequency components, and then suddenly goes back to the Inter-Ictal stage. However, identifying each stage from a time series is a non-trivial task. In particular, this work studies the identification of the Ictal stage during an epileptic episode. As most bioelectrical signals, an ECoS is a highly non-periodical and non-stationary signal. Moreover, ECoS from each seizure stage have their own features which characterize them. We identify the Ictal stage by analyzing short signal segments (epochs), based on the chaos like behavior shown by the signal. This was done by the application of the well known 0-1 Test of chaos. Signals are intracranially recorded from Wistar rats at cortex level, epileptic subjects of the Kindling model for whom seizures were elicited by electrical stimulation. Then as a result, we have a successfully identified the Ictal stage validated by the standard Diagnostic Test method.