Delta oscillation coupled propagating fast ripples precede epileptiform discharges in patients with focal epilepsy

Using macroelectrode stereo intracranial EEG (iEEG) recordings from a cohort of 46 patients we found that, in the seizure onset zone (SOZ), propagating fast ripple (FR) were more often followed by an epileptiform spike, as compared with non-propagating FR. Propagating FR had a distinct frequency and larger power and were more strongly phase coupled to the peak of iEEG delta oscillation, which likely correspond with the DOWN states during NREM sleep, than non-propagating FR. Thus, a sub-population of epileptiform spikes in the SOZ, are preceded by propagating FR that are coordinated by the DOWN state during NREM sleep.