title: Dynamic causal modelling of seizure activity in a rat model.
abstract: This paper presents a physiological account of seizure activity and its evolution over time using a rat model of induced epilepsy. We analyse spectral activity recorded in the hippocampi of three rats who received kainic acid injections in the right hippocampus. We use dynamic causal modelling of seizure activity and Bayesian model reduction to identify the key synaptic and connectivity parameters that underlie seizure onset. Using recent advances in hierarchical modelling (parametric empirical Bayes), we characterise seizure onset in terms of slow fluctuations in synaptic excitability of specific neuronal populations. Our results suggest differences in the pathophysiology - of seizure activity in the lesioned versus the non-lesioned hippocampus - with pronounced changes in excitation-inhibition balance and temporal summation on the lesioned side. In particular, our analyses suggest that marked reductions in the synaptic time constant of the deep pyramidal cells and the self-inhibition of inhibitory interneurons (in the lesioned hippocampus) are sufficient to explain changes in spectral activity. Although these synaptic changes are consistent over rats, the resulting electrophysiological phenotype can be quite diverse.
authors.affiliation: Department of Data-analysis, University of Ghent, B9000 Ghent, Belgium; INSERM U825, Purpan CHU Hospital, 31059 Toulouse Cedex 3, France.
authors.forename: Margarita
authors.initials: M
authors.lastname: Papadopoulou
authors.affiliation: The Wellcome Trust Centre for Neuroimaging, University College London, Queen Square, WC1N 3BG London, UK; Clinical Neurophysiology, Karolinska University Hospital, Stockholm, Sweden.
authors.forename: Gerald
authors.initials: G
authors.lastname: Cooray
authors.affiliation: The Wellcome Trust Centre for Neuroimaging, University College London, Queen Square, WC1N 3BG London, UK.
authors.forename: Richard
authors.initials: R
authors.lastname: Rosch
authors.affiliation: VTC Research Institute, Bradley Department of Electrical & Computer Engineering, Virginia Tech, United States.
authors.forename: Rosalyn
authors.initials: R
authors.lastname: Moran
authors.affiliation: Department of Data-analysis, University of Ghent, B9000 Ghent, Belgium.
authors.forename: Daniele
authors.initials: D
authors.lastname: Marinazzo
authors.affiliation: The Wellcome Trust Centre for Neuroimaging, University College London, Queen Square, WC1N 3BG London, UK.
authors.forename: Karl
authors.initials: K
authors.lastname: Friston
mesh_terms: D000818:Animals; D001499:Bayes Theorem; D004827:Epilepsy / Q000139:chemically induced / Q000503:physiopathology*; D006624:Hippocampus / Q000187:drug effects / Q000503:physiopathology*; D007608:Kainic Acid / Q000008:administration & dosage; D008959:Models, Neurological; D009474:Neurons / Q000502:physiology*; D017208:Rats, Wistar; D012640:Seizures / Q000139:chemically induced / Q000503:physiopathology*; D012815:Signal Processing, Computer-Assisted
chemical_list: D007608:Kainic Acid