title: High-frequency oscillations and mesial temporal lobe epilepsy.
abstract: The interest of epileptologists has recently shifted from the macroscopic analysis of interictal spikes and seizures to the microscopic analysis of short events in the EEG that are not visible to the naked eye but are observed once the signal has been filtered in specific frequency bands. With the use of new technologies that allow multichannel recordings at high sampling rates and the development of computer algorithms that permit the automated analysis of extensive amounts of data, it is now possible to extract high-frequency oscillations (HFOs) between 80 and 500Hz from the EEG; HFOs have been further categorised as ripples (80-200Hz) and fast ripples (250-500Hz). Within the context of epileptic disorders, HFOs should reflect the pathological activity of neural networks that sustain seizure generation, and could serve as biomarkers of epileptogenesis and ictogenesis. We review here the presumptive cellular mechanisms of ripples and fast ripples in mesial temporal lobe epilepsy. We also focus on recent findings regarding the occurrence of HFOs during epileptiform activity observed in in vitro models of epileptiform synchronization, in in vivo models of mesial temporal lobe epilepsy and in epileptic patients. Finally, we address the effects of anti-epileptic drugs on HFOs and raise some questions and issues related to the definition of HFOs.
authors.affiliation: Montreal Neurological Institute and Department of Neurology & Neurosurgery, McGill University, 3801 University Street, Montréal, QC, H3A 2B4, Canada.
authors.forename: Maxime
authors.initials: M
authors.lastname: Lévesque
authors.affiliation: Montreal Neurological Institute and Department of Neurology & Neurosurgery, McGill University, 3801 University Street, Montréal, QC, H3A 2B4, Canada.
authors.forename: Zahra
authors.initials: Z
authors.lastname: Shiri
authors.affiliation: Montreal Neurological Institute and Department of Neurology & Neurosurgery, McGill University, 3801 University Street, Montréal, QC, H3A 2B4, Canada.
authors.forename: Li-Yuan
authors.initials: LY
authors.lastname: Chen
authors.affiliation: Montreal Neurological Institute and Department of Neurology & Neurosurgery, McGill University, 3801 University Street, Montréal, QC, H3A 2B4, Canada. Electronic address: massimo.avoli@mcgill.ca.
authors.forename: Massimo
authors.initials: M
authors.lastname: Avoli
mesh_terms: D000818:Animals; D058256:Brain Waves / Q000187:drug effects / Q000502:physiology; D004569:Electroencephalography / Q000379:methods; D004827:Epilepsy / Q000188:drug therapy / Q000503:physiopathology*; D004833:Epilepsy, Temporal Lobe / Q000188:drug therapy* / Q000503:physiopathology*; D006801:Humans; D010862:Pilocarpine / Q000494:pharmacology*; D012640:Seizures / Q000188:drug therapy / Q000503:physiopathology*
chemical_list: D010862:Pilocarpine
keywords: Epileptogenesis; Fast ripples; High-frequency oscillations; Ictogenesis; Mesial temporal lobe epilepsy; Ripples