A Systems-Level Approach to Human Epileptic Seizures

• Published in: Neuroinformatics (Totowa, N.J.) N.J.), 2013-04, Vol.11 (2), p.159-173
• Main Authors: Rummel, Christian, Goodfellow, Marc, Gast, Heidemarie, Hauf, Martinus, Amor, Frédérique, Stibal, Alexander, Mariani, Luigi, Wiest, Roland, Schindler, Kaspar
• Format: Article
• Language: English
• Subjects: Adolescent; Adult; Analysis of Variance; Bioinformatics; Biological and medical sciences; Biomedical and Life Sciences; Biomedicine; Brain - pathology; Brain - physiopathology; Brain Waves - physiology; Computational Biology/Bioinformatics; Computer Appl. in Life Sciences; Electroencephalography; Epilepsy - diagnosis; Epilepsy - physiopathology; Female; Headache. Facial pains. Syncopes. Epilepsia. Intracranial hypertension. Brain oedema. Cerebral palsy; Humans; Male; Medical sciences; Models, Biological; Nervous system (semeiology, syndromes); Neurology; Neurosciences; Original Article; Statistics, Nonparametric
• ISSN: 1539-2791; 1559-0089
• DOI: 10.1007/s12021-012-9161-2

Epileptic seizures are due to the pathological collective activity of large cellular assemblies. A better understanding of this collective activity is integral to the development of novel diagnostic and therapeutic procedures. In contrast to reductionist analyses, which focus solely on small-scale characteristics of ictogenesis, here we follow a systems-level approach, which combines both small-scale and larger-scale analyses. Peri-ictal dynamics of epileptic networks are assessed by studying correlation within and between different spatial scales of intracranial electroencephalographic recordings (iEEG) of a heterogeneous group of patients suffering from pharmaco-resistant epilepsy. Epileptiform activity as recorded by a single iEEG electrode is determined objectively by the signal derivative and then subjected to a multivariate analysis of correlation between all iEEG channels. We find that during seizure, synchrony increases on the smallest and largest spatial scales probed by iEEG. In addition, a dynamic reorganization of spatial correlation is observed on intermediate scales, which persists after seizure termination. It is proposed that this reorganization may indicate a balancing mechanism that decreases high local correlation. Our findings are consistent with the hypothesis that during epileptic seizures hypercorrelated and therefore functionally segregated brain areas are re-integrated into more collective brain dynamics. In addition, except for a special sub-group, a highly significant association is found between the location of ictal iEEG activity and the location of areas of relative decrease of localised EEG correlation. The latter could serve as a clinically important quantitative marker of the seizure onset zone (SOZ).