Pathological high-frequency oscillations (HFOs) (80–800 Hz) are considered biomarkers of epileptogenic tissue, but the underlying complex neuronal events are not well understood. Here, we identify and discuss several outstanding issues or conundrums in regards to the recording, analysis, and interpretation of HFOs in the epileptic brain to critically highlight what is known and what is not about these enigmatic events. High-frequency oscillations reflect a range of neuronal processes contributing to overlapping frequencies from the lower 80 Hz to the very fast spectral frequency bands. Given their complex neuronal nature, HFOs are extremely sensitive to recording conditions and analytical approaches. We provide a list of recommendations that could help to obtain comparable HFO signals in clinical and basic epilepsy research. Adopting basic standards will facilitate data sharing and interpretation that collectively will aid in understanding the role of HFOs in health and disease for translational purpose.
*Department of Functional and Systems Neuroscience, Instituto Cajal, CSIC, Madrid, Spain;
†Departmentof Neurology, David Geffen School of Medicine, University of California, Los Angeles, California, U.S.A.; and
‡Department of Electrical and Computer Engineering, University of Toronto, Toronto, ON, Canada.
Address correspondence and reprint requests to Liset Menendez de la Prida, PhD, Instituto Cajal, CSIC, Ave Doctor Arce 37, 28002 Madrid, Spain; e-mail: firstname.lastname@example.org.
This study was supported by grants from different agencies including, the Spanish Ministry of Economy (BFU2012–37156-C03-01) and the Intramural CSIC Grant 201220E084 to L. M. de la Prida and NINDS (NS 071048) to R. J. Staba.