Abstracts

Rationale: We address the question whether directed interactions between brain regions of epilepsy patients differ from those of healthy controls even during the seizure-free interval. Furthermore we investigate whether these differences may help to identify the seizure generating area and whether this area preferentially drives or is driven by other brain regions. Methods: We analyzed EEG data recorded under a resting-state eyes-open and eyes-closed condition from 23 healthy controls and from 21 epilepsy patients with different cerebral locations of the seizure generating area. We used two approaches to measure directed interactions, namely Granger-causality (GC) and symbolic transfer entropy (STE). Results: During the eyes-open condition widespread directed interactions could be observed between different brain regions in both the patient and the control group. For the latter group, particularly the occipital regions appeared to preferentially drive other brain regions during the eyes-closed condition. For the patient group, other brain regions exhibited an even stronger driving, and in the majority of cases these driving regions coincided with the approximate location of the seizure generating area. GC and STE detected these driving regions with a different sensitivity. Conclusions: Our findings indicate that the epileptic focus preferentially drives other brain regions even during the seizure-free interval although this driving appears to depend on the state of vigilance. Relevant information about the seizure generating area and its interactions within the epileptic network can be assessed by analyzing the directionality of interactions. (This work was supported by the Deutsche Forschungsgemeinschaft)