Abstract
Hypersynchronous network activity is the defining hallmark of epilepsy and manifests in a wide spectrum of phenomena, of which electrographic activity during seizures is only one extreme. The aim of this study was to differentiate between different types of epileptiform activity (EA) patterns and investigate their temporal succession and interactions. We analyzed local field potentials (LFPs) from freely behaving male mice that had received an intrahippocampal kainate injection to model mesial temporal lobe epilepsy (MTLE). Epileptiform spikes occurred in distinct bursts. Using machine learning, we derived a scale reflecting the spike load of bursts and three main burst categories that we labeled high-load, medium-load, and low-load bursts. We found that bursts of these categories were non-randomly distributed in time. High-load bursts formed clusters and were typically surrounded by transition phases with increased rates of medium-load and low-load bursts. In apparent contradiction to this, increased rates of low-load bursts were also associated with longer background phases, i.e., periods lacking high-load bursting. Furthermore, the rate of low-load bursts was more strongly correlated with the duration of background phases than the overall rate of epileptiform spikes. Our findings are consistent with the hypothesis that low-level EA could promote network stability but could also participate in transitions towards major epileptiform events, depending on the current state of the network.
- electrographic seizures
- epileptic spikes
- epileptiform activity
- hippocampus
- interictal activity
- mesial temporal lobe epilepsy
Footnotes
The authors declare no competing financial interests.
This work was supported by the German Research Foundation as part of the Cluster of Excellence BrainLinks-BrainTools within the framework of the German Excellence Initiative (Grant EXC 1086, to U.E., A. Kumar, and C.A.H.) and through Grant INST 39/963-1 FUGG (bwForCluster NEMO), the State of Baden-Wuerttemberg through bwHPC, and by the Federal Ministry of Education and Research (BMBF) Grants FKZ 1GQ0830 and 16PGF0070 (to U.E.), co-financed by the European Union/European Regional Development Fund (TIGER, A31). The article processing charge was funded by the German Research Foundation (DFG) and the University of Freiburg in the funding programme Open Access Publishing.
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