Spontaneous and visually driven high-frequency oscillations in the occipital cortex: Intracranial recording in epileptic patients

Authors

  • Tetsuro Nagasawa,

    1. Department of Pediatrics, Children's Hospital of Michigan, Wayne State University, Detroit Medical Center, Detroit, Michigan
    2. Department of Pediatrics and Developmental Biology, Tokyo Medical and Dental University, Tokyo, Japan
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  • Csaba Juhász,

    1. Department of Pediatrics, Children's Hospital of Michigan, Wayne State University, Detroit Medical Center, Detroit, Michigan
    2. Department of, Neurology, Children's Hospital of Michigan, Wayne State University, Detroit Medical Center, Detroit, Michigan
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  • Robert Rothermel,

    1. Department of Psychiatry, Children's Hospital of Michigan, Wayne State University, Detroit Medical Center, Detroit, Michigan
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  • Karsten Hoechstetter,

    1. BESA GmbH, Munich, Germany
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  • Sandeep Sood,

    1. Department of Neurosurgery, Children's Hospital of Michigan, Wayne State University, Detroit Medical Center, Detroit, Michigan
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  • Eishi Asano

    Corresponding author
    1. Department of Pediatrics, Children's Hospital of Michigan, Wayne State University, Detroit Medical Center, Detroit, Michigan
    2. Department of Pediatrics and Developmental Biology, Tokyo Medical and Dental University, Tokyo, Japan
    • Medical Director of Electroneurodiagnostics, Associate Professor of Pediatrics and Neurology, Division of Pediatric Neurology, Children's Hospital of Michigan, Wayne State University, Room 3C125, 3901 Beaubien St., Detroit, Michigan, 48201, USA
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Abstract

High-frequency oscillations (HFOs) at ≥80 Hz of nonepileptic nature spontaneously emerge from human cerebral cortex. In 10 patients with extraoccipital lobe epilepsy, we compared the spectral-spatial characteristics of HFOs spontaneously arising from the nonepileptic occipital cortex with those of HFOs driven by a visual task as well as epileptogenic HFOs arising from the extraoccipital seizure focus. We identified spontaneous HFOs at ≥80 Hz with a mean duration of 330 ms intermittently emerging from the occipital cortex during interictal slow-wave sleep. The spectral frequency band of spontaneous occipital HFOs was similar to that of visually driven HFOs. Spontaneous occipital HFOs were spatially sparse and confined to smaller areas, whereas visually driven HFOs involved the larger areas including the more rostral sites. Neither spectral frequency band nor amplitude of spontaneous occipital HFOs significantly differed from those of epileptogenic HFOs. Spontaneous occipital HFOs were strongly locked to the phase of delta activity, but the strength of δ-phase coupling decayed from 1 to 3 Hz. Conversely, epileptogenic extraoccipital HFOs were locked to the phase of delta activity about equally in the range from 1 to 3 Hz. The occipital cortex spontaneously generates physiological HFOs which may stand out on electrocorticography traces as prominently as pathological HFOs arising from elsewhere; this observation should be taken into consideration during presurgical evaluation. Coupling of spontaneous delta and HFOs may increase the understanding of significance of δ-oscillations during slow-wave sleep. Further studies are warranted to determine whether δ-phase coupling distinguishes physiological from pathological HFOs or simply differs across anatomical locations. Hum Brain Mapp , 2012. © 2011 Wiley Periodicals, Inc.

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