Time-variant connectivity analysis between epileptic EEG signals and between EEG-envelopes and HRV

This study investigates the connectivity between EEG signals (cortical connectivity - CC) as well as between EEG-envelopes and heart rate variability (cortical-neurovegetative connectivity - CNC) by using time-variant Partial Directed Coherence analysis (for CC) and Wavelet Coherence (for CNC). Data from 18 patients suffering from temporal lobe epilepsy has been used to test our methodological approaches. The analysis intervals contain 5 min before and 5 min after seizure onset. Accordingly, the dynamics of the CC and CNC connectivity networks can be studied before, during and after the seizure. Our results concerning CC (1.5 - 4 Hz) demonstrate that the same lateralization of interaction networks exists before and during seizure, i.e. the interaction networks are clearly on the side of the epileptic focus. Additionally, the number of interactions is increased during the seizure. All results with regard to CNC support our hypothesis of interrelations between the neurovegetative system and cortical brain structures.