Abstracts

Rationale: Network connectivity is a main organizing principle of the brain, and it plays a pivotal role in the pathophysiology of epilepsy. It is assumed that specific components of the network are crucial for seizure initiation, while others parts are involved mainly propagation or maintenance of seizure activity. In this study, we have examined whether analysis of effective connectivity can provide insights into the role of specific network components in seizures in humans. Methods: Intracranial recording of eight patients (36 seizures) implanted with subdural and/or depth electrodes were analyzed. The synchronization between channels was estimated using coherence while directed effective connectivity was determined by modified directed Direct Transfer Function. Results: At the onset of a seizure, the synchronization profile within seizure onset zone (SOZ) was characterized by high coherence while in surrounding areas (SA) the coherence was low initially and increased with the progression seizure. These changes were accompanied by a decreased connectivity within the SOZ and decrease of outflow connectivity between SOZ and SA at the frequency band 20-250 Hz. During advanced stages of a seizure, the analogous connectivity changes are present in spatially limited brain areas which are outside SOZ and which are involved in seizure aktivity. Conclusions: This study suggests that identified change in network connectivity differentiates tissue which is actively generating ictal activity from the tissue into which seizures only propagate via synaptic activity, but do not actively participate in seizure genesis. Funding: The study was supported by Czech Ministry of Health AZV grant 15-29835A.