Significance of high-frequency electrical brain activity

Katsuhiro Kobayashi, Tomoyuki Akiyama, Takashi Agari, Tatsuya Sasaki, Takashi Shibata, Yoshiyuki Hanaoka, Mari Akiyama, Fumika Endoh, Makio Oka, Isao Date

Research output: Contribution to journalReview articlepeer-review

6 Citations (Scopus)


Electroencephalogram (EEG) data include broadband electrical brain activity ranging from infra-slow bands ( < 0.1 Hz) to traditional frequency bands (e.g., the approx. 10 Hz alpha rhythm) to high-frequency bands of up to 500 Hz. High-frequency oscillations (HFOs) including ripple and fast ripple oscillations (80-200 Hz and > 200 / 250 Hz, respectively) are particularly of note due to their very close relationship to epileptogenicity, with the possibility that they could function as a surrogate biomarker of epileptogenicity. In contrast, physiological high-frequency activity plays an important role in higher brain functions, and the differentiation between pathological / epileptic and physiological HFOs is a critical issue, especially in epilepsy surgery. HFOs were initially recorded with intracranial electrodes in patients with intractable epilepsy as part of a long-term invasive seizure monitoring study. However, fast oscillations (FOs) in the ripple and gamma bands (40-80 Hz) are now noninvasively detected by scalp EEG and magnetoencephalography, and thus the scope of studies on HFOs /FOs is rapidly expanding.

Original languageEnglish
Pages (from-to)191-200
Number of pages10
JournalActa medica Okayama
Issue number3
Publication statusPublished - 2017


  • Electroencephalogram
  • Epilepsy
  • Fast oscillations
  • High-frequency oscillations
  • Time-frequency analysis

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)


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