title: Deviations from Critical Dynamics in Interictal Epileptiform Activity.
abstract: The framework of criticality provides a unifying perspective on neuronal dynamics from in vitro cortical cultures to functioning human brains. Recent findings suggest that a healthy cortex displays critical dynamics, giving rise to scale-free spatiotemporal cascades of activity, termed neuronal avalanches. Pharmacological manipulations of the excitation-inhibition balance (EIB) in cortical cultures were previously shown to result in deviations from criticality and from the power law scaling of avalanche size distribution. To examine the sensitivity of neuronal avalanche metrics to altered EIB in humans, we focused on epilepsy, a neurological disorder characterized by hyperexcitable networks. Using magnetoencephalography, we quantitatively assessed deviations from criticality in the brain dynamics of patients with epilepsy during interictal (between-seizures) activity. Compared with healthy control subjects, epilepsy patients tended to exhibit a higher neural gain and larger avalanches, particularly during interictal epileptiform activity. Moreover, deviations from scale-free behavior were exclusively connected to brief intervals at epileptiform discharges, strengthening the association between deviations from criticality and the instantaneous changes in EIB. The avalanches collected during interictal epileptiform activity had not only a stereotypical size range but also involved particular spatial patterns of activations, as expected for periods of epileptic network dominance. Overall, the neuronal avalanche metrics provide a quantitative novel description of interictal brain activity of patients with epilepsy.
  
  
  
  Healthy brain dynamics requires a delicate balance between excitatory and inhibitory processes. Several brain disorders, such as epilepsy, are associated with altered excitation-inhibition balance, but assessing this balance using noninvasive tools is still challenging. In this study, we apply the framework of critical brain dynamics to data from epilepsy patients, which were recorded between seizures. We show that metrics of criticality provide a sensitive tool for noninvasive assessment of changes in the balance. Specifically, brain activity of epilepsy patients deviates from healthy critical brain dynamics, particularly during abnormal epileptiform activity. The study offers a novel quantitative perspective on epilepsy and its relation to healthy brain dynamics.
authors.affiliation: Leslie and Susan Gonda (Goldschmied) Multidisciplinary Brain Research Center, Bar-Ilan University, 5290002 Ramat Gan, Israel, Oshrit.Arviv@biu.ac.il.
authors.forename: Oshrit
authors.initials: O
authors.lastname: Arviv
authors.affiliation: Brain Function Imaging Unit, Tel-Aviv Sourasky Medical Center, 6423906 Tel-Aviv, Israel.|BioMag Laboratory, HUS Medical Imaging Center, University of Helsinki and Helsinki University Hospital, 00014 Helsinki Finland.
authors.forename: Mordekhay
authors.initials: M
authors.lastname: Medvedovsky
authors.affiliation: Department of Biomedical Engineering, Ben-Gurion University of the Negev, 8410501 Beer-Sheva, Israel.|The Inter-Faculty School for Brain Sciences, Zlotowski Center for Neuroscience, Ben-Gurion University of the Negev, 8410501 Beer-Sheva, Israel, and.
authors.forename: Liron
authors.initials: L
authors.lastname: Sheintuch
authors.affiliation: Leslie and Susan Gonda (Goldschmied) Multidisciplinary Brain Research Center, Bar-Ilan University, 5290002 Ramat Gan, Israel.|Department of Psychology, Bar-Ilan University, 5290002 Ramat Gan, Israel.
authors.forename: Abraham
authors.identifier: 0000-0002-9349-0621
authors.initials: A
authors.lastname: Goldstein
authors.affiliation: Department of Cognitive and Brain Sciences, Ben-Gurion University of the Negev, 8410501 Beer-Sheva, Israel.|The Inter-Faculty School for Brain Sciences, Zlotowski Center for Neuroscience, Ben-Gurion University of the Negev, 8410501 Beer-Sheva, Israel, and.|Department of Computer Science, Ben-Gurion University of the Negev, 8410501 Beer-Sheva, Israel.
authors.forename: Oren
authors.identifier: 0000-0003-1129-4799
authors.initials: O
authors.lastname: Shriki
mesh_terms: D000200:Action Potentials; D001921:Brain / Q000503:physiopathology*; D001931:Brain Mapping; D002648:Child; D003198:Computer Simulation; D004827:Epilepsy / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008959:Models, Neurological; D015233:Models, Statistical; D009415:Nerve Net / Q000503:physiopathology*; D055815:Young Adult
keywords: MEG; criticality; epileptiform; excitation-inhibition balance; interictal