Heidemarie Gast1, Johannes Niediek1, Kaspar Schindler2, Jan Boström3, Volker A Coenen3, Heinz Beck4, Christian E Elger1, Florian Mormann5. 1. Cognitive and Clinical Neurophysiology, Department of Epileptology, University of Bonn, Bonn, Germany. 2. Department of Neurology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland. 3. Stereotaxy and MR-Based OR Techniques, Department of Neurosurgery, University of Bonn, Bonn, Germany. 4. Laboratory for Experimental Epileptology and Cognition Research, Department of Epileptology, University of Bonn, Bonn, Germany. 5. Cognitive and Clinical Neurophysiology, Department of Epileptology, University of Bonn, Bonn, Germany. Electronic address: florian.mormann@ukb.uni-bonn.de.
Abstract
OBJECTIVE: To better understand the mechanisms that lead to the sudden and unexpected occurrence of seizures, with the neuronal correlate being abnormally synchronous discharges that disrupt neuronal function. METHODS: To address this problem, we recorded single neuron activity in epilepsy patients during the transition to seizures to uncover specific changes of neuronal firing patterns. We focused particularly on neurons repeatedly firing discrete groups of high-frequency action potentials (so called bursters) that have been associated with ictogenesis. We analyzed a total of 459 single neurons and used the mean autocorrelation time as a quantitative measure of burstiness. To unravel the intricate roles of excitation and inhibition, we also examined differential contributions from putative principal cells and interneurons. RESULTS: During interictal recordings, burstiness was significantly higher in the seizure onset hemisphere, an effect found only for principal cells, but not for interneurons, and which disappeared before seizures. CONCLUSION: These findings deviate from conventional views of ictogenesis that propose slowly-increasing aggregates of bursting neurons which give rise to seizures once they reach a critical mass. SIGNIFICANCE: Instead our results are in line with recent hypotheses that bursting may represent a protective mechanism by preventing direct transmission of postsynaptic high-frequency oscillations.
OBJECTIVE: To better understand the mechanisms that lead to the sudden and unexpected occurrence of seizures, with the neuronal correlate being abnormally synchronous discharges that disrupt neuronal function. METHODS: To address this problem, we recorded single neuron activity in epilepsypatients during the transition to seizures to uncover specific changes of neuronal firing patterns. We focused particularly on neurons repeatedly firing discrete groups of high-frequency action potentials (so called bursters) that have been associated with ictogenesis. We analyzed a total of 459 single neurons and used the mean autocorrelation time as a quantitative measure of burstiness. To unravel the intricate roles of excitation and inhibition, we also examined differential contributions from putative principal cells and interneurons. RESULTS: During interictal recordings, burstiness was significantly higher in the seizure onset hemisphere, an effect found only for principal cells, but not for interneurons, and which disappeared before seizures. CONCLUSION: These findings deviate from conventional views of ictogenesis that propose slowly-increasing aggregates of bursting neurons which give rise to seizures once they reach a critical mass. SIGNIFICANCE: Instead our results are in line with recent hypotheses that bursting may represent a protective mechanism by preventing direct transmission of postsynaptic high-frequency oscillations.
Authors: Dina Simkin; Kelly A Marshall; Carlos G Vanoye; Reshma R Desai; Bernabe I Bustos; Brandon N Piyevsky; Juan A Ortega; Marc Forrest; Gabriella L Robertson; Peter Penzes; Linda C Laux; Steven J Lubbe; John J Millichap; Alfred L George; Evangelos Kiskinis Journal: Elife Date: 2021-02-05 Impact factor: 8.713
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