The identification of distinct high-frequency oscillations during spikes delineates the seizure onset zone better than high-frequency spectral power changes

•High frequency power increases and decreases during spikes do not occur in the same brain regions as high frequency oscillations (HFO).•HFO indicate regions of seizure onset better than high frequency power changes during spikes.•Significant HF decreases are most prominent over regions of seizure onset.

ObjectiveInterictal high-frequency oscillations (HFOs, 80-500 Hz) can predict the seizure onset zone (SOZ), but visual detection of HFOs is time consuming. Time-frequency analysis can reveal large high-frequency (HF) power changes (80-500 Hz) associated with inter-ictal spikes. The present study determines how well the rate of HFOs and spike-related HF power changes were co-localized with SOZ.MethodsWe analyzed 583 channels (68 in the SOZ) sampled from 14 patients who underwent intracranial EEG recording. We determined if the rate of visually-marked HFOs and spike-related HF power changes differed between SOZ and non-SOZ.ResultsSignificantly higher rates of HFOs were found in SOZ. The degree of spike-related HF power augmentation failed to differ between SOZ and non-SOZ, whereas that of post-spike HF power attenuation was significantly more severe in SOZ compared to in non-SOZ. Regions showing HFOs and large spike-related HF-changes showed a partial overlap in distribution in 7/14 patients.ConclusionsStrong HF augmentation during spikes and high HFO rates occurred over different brain locations. The rate of HFOs showed the best performance in identifying SOZ. Post-spike HF power attenuation may represent increased inhibition in these channels and should be investigated further.SignificanceStrong HF power changes during spikes and HFOs per se seem to reflect distinct phenomena.