Continuous High Frequency Activity: a peculiar SEEG pattern related to specific brain regions

Clin Neurophysiol. 2013 Aug;124(8):1507-16. doi: 10.1016/j.clinph.2012.11.016. Epub 2013 Jun 12.


Objective: While visually marking the high frequency oscillations in the stereo-EEG of epileptic patients, we observed a continuous/semicontinuous activity in the ripple band (80-250 Hz), which we defined continuous High Frequency Activity (HFA). We aim to analyze in all brain regions the occurrence and significance of this particular pattern.

Methods: Twenty patients implanted in mesial temporal and neocortical areas were studied. One minute of slow-wave sleep was reviewed. The background was classified as continuous/semicontinuous, irregular, or sporadic based on the duration of the fast oscillations. Each channel was classified as inside/outside the seizure onset zone (SOZ) or a lesion.

Results: The continuous/semicontinuous HFA occurred in 54 of the 790 channels analyzed, with a clearly higher prevalence in hippocampus and occipital lobe. No correlation was found with the SOZ or lesions. In the occipital lobe the continuous/semicontinuous HFA was present independently of whether eyes were open or closed.

Conclusions: We describe what appears to be a new physiological High Frequency Activity, independent of epileptogenicity, present almost exclusively in the hippocampus and occipital cortex but independent of the alpha rhythm.

Significance: The continuous HFA may be an intrinsic characteristic of specific brain regions, reflecting a particular type of physiological neuronal activity.

Keywords: HFOs; High Frequency Activity; Intracerebral electrodes; Neocortical regions; SEEG.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Brain / physiopathology*
  • Brain Mapping
  • Electrodes, Implanted
  • Electroencephalography / methods*
  • Epilepsy / physiopathology*
  • Female
  • Humans
  • Male
  • Occipital Lobe / physiopathology
  • Seizures / physiopathology
  • Sleep / physiology