title: Dynamics of interictal spikes and high-frequency oscillations during epileptogenesis in temporal lobe epilepsy.
abstract: Mesial temporal lobe epilepsy (MTLE) is characterized in humans and in animal models by a seizure-free latent phase that follows an initial brain insult; this period is presumably associated to plastic changes in temporal lobe excitability and connectivity. Here, we analyzed the occurrence of interictal spikes and high frequency oscillations (HFOs; ripples: 80-200Hz and fast ripples: 250-500Hz) from 48h before to 96h after the first seizure in the rat pilocarpine model of MTLE. Interictal spikes recorded with depth EEG electrodes from the hippocampus CA3 area and entorhinal cortex (EC) were classified as type 1 (characterized by a spike followed by a wave) or type 2 (characterized by a spike with no wave). We found that: (i) there was a switch in the distribution of both types of interictal spikes before and after the occurrence of the first seizure; during the latent phase both types of interictal spikes predominated in the EC whereas during the chronic phase both types of spikes predominated in CA3; (ii) type 2 spike duration decreased in both regions from the latent to the chronic phase; (iii) type 2 spikes associated to fast ripples occurred at higher rates in EC compared to CA3 during the latent phase while they occurred at similar rates in both regions in the chronic phase; and (iv) rates of fast ripples outside of spikes were higher in EC compared to CA3 during the latent phase. Our findings demonstrate that the transition from the latent to the chronic phase is paralleled by dynamic changes in interictal spike and HFO expression in EC and CA3. We propose that these changes may represent biomarkers of epileptogenicity in MTLE.
authors.affiliation: Montreal Neurological Institute and Departments of Neurology & Neurosurgery and of Physiology, McGill University, Montréal, H3A 2B4 QC, Canada.
authors.forename: Pariya
authors.initials: P
authors.lastname: Salami
authors.affiliation: Montreal Neurological Institute and Departments of Neurology & Neurosurgery and of Physiology, McGill University, Montréal, H3A 2B4 QC, Canada.
authors.forename: Maxime
authors.initials: M
authors.lastname: Lévesque
authors.affiliation: Montreal Neurological Institute and Departments of Neurology & Neurosurgery and of Physiology, McGill University, Montréal, H3A 2B4 QC, Canada.
authors.forename: Ruba
authors.initials: R
authors.lastname: Benini
authors.affiliation: Montreal Neurological Institute and Departments of Neurology & Neurosurgery and of Physiology, McGill University, Montréal, H3A 2B4 QC, Canada.
authors.forename: Charles
authors.initials: C
authors.lastname: Behr
authors.affiliation: Montreal Neurological Institute and Departments of Neurology & Neurosurgery and of Physiology, McGill University, Montréal, H3A 2B4 QC, Canada.
authors.forename: Jean
authors.initials: J
authors.lastname: Gotman
authors.affiliation: Montreal Neurological Institute and Departments of Neurology & Neurosurgery and of Physiology, McGill University, Montréal, H3A 2B4 QC, Canada. Electronic address: massimo.avoli@mcgill.ca.
authors.forename: Massimo
authors.initials: M
authors.lastname: Avoli
mesh_terms: D000818:Animals; D001921:Brain / Q000503:physiopathology*; D004569:Electroencephalography; D004833:Epilepsy, Temporal Lobe / Q000503:physiopathology*; D008297:Male; D010862:Pilocarpine; D051381:Rats; D017207:Rats, Sprague-Dawley; D012640:Seizures / Q000139:chemically induced / Q000503:physiopathology*
chemical_list: D010862:Pilocarpine
keywords: Epileptogenesis; High-frequency oscillations; Interictal spikes; Temporal lobe epilepsy