Data mining neocortical high-frequency oscillations in epilepsy and controls

Justin A. Blanco, Matt Stead, Abba Krieger, William Stacey, Douglas Maus, Eric Marsh, Jonathan Viventi, Kendall H. Lee, Richard Marsh, Brian Litt, Gregory A. Worrell

Research output: Contribution to journalArticlepeer-review

94 Scopus citations


Transient high-frequency (100-500Hz) oscillations of the local field potential have been studied extensively in human mesial temporal lobe. Previous studies report that both ripple (100-250Hz) and fast ripple (250-500Hz) 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=137Hz is increased in the seizure-onset zone more frequently than a cluster of fast ripple frequency oscillations (median spectral centroid=305Hz); (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 100-500Hz 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.

Original languageEnglish (US)
Pages (from-to)2948-2959
Number of pages12
Issue number10
StatePublished - Oct 2011


  • epilepsy
  • high-frequency oscillations
  • intracranial EEG

ASJC Scopus subject areas

  • Clinical Neurology


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