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

Area of Science:

• Neuroscience
• Epileptology

Background:

• High-frequency oscillations (HFOs) are crucial in epilepsy research.
• Continuous/semicontinuous HFOs in the ripple band (80-250 Hz) were observed during stereo-EEG monitoring.

Purpose of the Study:

• To analyze the occurrence and significance of continuous High Frequency Activity (HFA) across all brain regions.
• To characterize this HFA pattern in relation to epileptogenicity and specific brain areas.

Main Methods:

• Stereo-EEG data from 20 patients during slow-wave sleep were analyzed.
• Channels were classified based on HFA patterns (continuous/semicontinuous, irregular, sporadic) and location (seizure onset zone, lesion).

Main Results:

• Continuous/semicontinuous HFA was found in 54 of 790 channels, predominantly in the hippocampus and occipital lobe.
• No correlation was observed between continuous HFA and seizure onset zones or lesions.
• Occipital HFA occurred regardless of eye state (open/closed).

Conclusions:

• A novel physiological High Frequency Activity (HFA) is described, independent of epileptogenicity.
• This HFA appears intrinsic to specific brain regions like the hippocampus and occipital cortex.
• It may represent a distinct type of physiological neuronal activity.