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High‐Frequency Oscillations in the Normal Human Brain
Author(s) -
Frauscher Birgit,
von Ellenrieder Nicolás,
Zelmann Rina,
Rogers Christine,
Nguyen Dang Khoa,
Kahane Philippe,
Dubeau François,
Gotman Jean
Publication year - 2018
Publication title -
annals of neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.764
H-Index - 296
eISSN - 1531-8249
pISSN - 0364-5134
DOI - 10.1002/ana.25304
Subject(s) - postcentral gyrus , planum temporale , temporal lobe , occipital lobe , neuroscience , psychology , temporal cortex , parietal lobe , cortex (anatomy) , audiology , anatomy , epilepsy , medicine , functional magnetic resonance imaging
Objective High‐frequency oscillations (HFOs) are a promising biomarker for the epileptogenic zone. It has not been possible, however, to differentiate physiological from pathological HFOs, and baseline rates of HFO occurrence vary substantially across brain regions. This project establishes region‐specific normative values for physiological HFOs and high‐frequency activity (HFA). Methods Intracerebral stereo‐encephalographic recordings with channels displaying normal physiological activity from nonlesional tissue were selected from 2 tertiary epilepsy centers. Twenty‐minute sections from N2/N3 sleep were selected for automatic detection of ripples (80–250Hz), fast ripples (>250Hz), and HFA defined as long‐lasting activity > 80Hz. Normative values are provided for 17 brain regions. Results A total of 1,171 bipolar channels with normal physiological activity from 71 patients were analyzed. The highest rates of ripples were recorded in the occipital cortex, medial and basal temporal region, transverse temporal gyrus and planum temporale, pre‐ and postcentral gyri, and medial parietal lobe. The mean rate of fast ripples was very low (0.038/min). Only 5% of channels had a rate > 0.2/min HFA was observed in the medial occipital lobe, pre‐ and postcentral gyri, transverse temporal gyri and planum temporale, and lateral occipital lobe. Interpretation This multicenter atlas is the first to provide region‐specific normative values for physiological HFO rates and HFA in common stereotactic space; rates above these can now be considered pathological. Physiological ripples are frequent in eloquent cortex. In contrast, physiological fast ripples are very rare, making fast ripples a good candidate for defining the epileptogenic zone. Ann Neurol 2018;84:374–385