Dynamical analysis of brain seizure activity from EEG signals

A sudden emergence of seizure activity on a normal background EEG can be seen from visual inspection of the intracranial EEG (iEEG) recordings of Genetic Absence Epilepsy Rat from Strasbourg (GAERS). We observe that most of the recording channels from different brain regions display seizure activity. We wonder if the brain behavior changes within a given seizure. Using source separation methods on temporal sliding windows, we develop a map of dynamic behavior to study this dynamicity. The map is built by computing the correlation functions between the main sources extracted in different time windows. The proposed method is applied on iEEG of four GAERS. We see that the behavior of brain changes about 0.5s - 1.5s after onset when the relevant temporal sources become very similar. The corresponding spatial maps for each time window shows that the seizure activity starts from a focus and propagates quickly.