title: Data mining neocortical high-frequency oscillations in epilepsy and controls.
abstract: Transient high-frequency (100-500 Hz) oscillations of the local field potential have been studied extensively in human mesial temporal lobe. Previous studies report that both ripple (100-250 Hz) and fast ripple (250-500 Hz) oscillations are increased in the seizure-onset zone of patients with mesial temporal lobe epilepsy. Comparatively little is known, however, about their spatial distribution with respect to seizure-onset zone in neocortical epilepsy, or their prevalence in normal brain. We present a quantitative analysis of high-frequency oscillations and their rates of occurrence in a group of nine patients with neocortical epilepsy and two control patients with no history of seizures. Oscillations were automatically detected and classified using an unsupervised approach in a data set of unprecedented volume in epilepsy research, over 12 terabytes of continuous long-term micro- and macro-electrode intracranial recordings, without human preprocessing, enabling selection-bias-free estimates of oscillation rates. There are three main results: (i) a cluster of ripple frequency oscillations with median spectral centroid = 137 Hz is increased in the seizure-onset zone more frequently than a cluster of fast ripple frequency oscillations (median spectral centroid = 305 Hz); (ii) we found no difference in the rates of high frequency oscillations in control neocortex and the non-seizure-onset zone neocortex of patients with epilepsy, despite the possibility of different underlying mechanisms of generation; and (iii) while previous studies have demonstrated that oscillations recorded by parenchyma-penetrating micro-electrodes have higher peak 100-500 Hz frequencies than penetrating macro-electrodes, this was not found for the epipial electrodes used here to record from the neocortical surface. We conclude that the relative rate of ripple frequency oscillations is a potential biomarker for epileptic neocortex, but that larger prospective studies correlating high-frequency oscillations rates with seizure-onset zone, resected tissue and surgical outcome are required to determine the true predictive value.
authors: Department of Electrical and Computer Engineering, United States Naval Academy, Annapolis, MD 21402, USA. blanco@usna.edu
authors: Justin A
authors: JA
authors: Blanco
authors: Matt
authors: M
authors: Stead
authors: Abba
authors: A
authors: Krieger
authors: William
authors: W
authors: Stacey
authors: Douglas
authors: D
authors: Maus
authors: Eric
authors: E
authors: Marsh
authors: Jonathan
authors: J
authors: Viventi
authors: Kendall H
authors: KH
authors: Lee
authors: Richard
authors: R
authors: Marsh
authors: Brian
authors: B
authors: Litt
authors: Gregory A
authors: GA
authors: Worrell
mesh_terms: D000328:Adult; D001931:Brain Mapping / Q000379:methods; D058256:Brain Waves / Q000502:physiology*; D004567:Electrodes, Implanted; D004569:Electroencephalography / Q000379:methods; D004827:Epilepsy / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D019579:Neocortex / Q000503:physiopathology*; D011446:Prospective Studies