High Frequency Oscillations

High frequency oscillations (HFOs), as the name suggests, are short duration events on EEG of high frequency (>80 Hz), resulting in an event resembling a ‘ripple’ in the EEG recording. These events are thought to indicate brief periods of hypersynchronicity from a local neighborhood of neurons, which are a precursor to the more global whole brain hypersynchornicity exhibited during seizures. Studies have shown that HFOs are more specific to seizure generating tissue than other markers, such as interictal epileptifom discharges, making them promising as a new clinical marker for presurgical investigation. We aim to expand on our knowledge of the properties of HFOs as well as resolve barriers to their use in clinical practice.

HFOs are most easily detected using intracranial EEG, and we have begun investigating HFOs captured during our simultaneous intracranial EEG-fMRI studies. This will allow us to explore the hemodynamic response to HFOs, and further explore the relationship between HFOs and epilepsy, especially as it relates to its capacity to serve as a marker of epileptogenic tissue. Functional connectivity analyses of this data will further allow us to explore networks responsible for HFO generation.

Although HFOs are produced under pathological conditions such as epilepsy, they may also be produced physiologically in healthy individuals and in healthy brain tissue. This issue poses a significant barrier to the clinical use of HFOs, and while methods for distinguishing between physiologic and pathologic HFOs exist, time constraints keep them from being clinically useful. We are currently exploring methods of algorithmically separating pathologic and physiologic HFOs for feasible use during clinical practice.

Click here to see our most recent paper on HFO detection, and here to see our most recent paper on HFOs and interictal EEG-fMRI.