High-Frequency Oscillations in Chemically Induced Spike-and-Wave Epileptic Seizures

High-frequency oscillations (HFO, 100-600 Hz) are thought to play an important role in epileptogenesis and development of seizures. HFO are subclassified in ripples (R, 100-200 Hz) and fast ripples (FR, 200-600 Hz), but it is unclear if both subclasses can be related to epilepsy. In this study, we have investigated R and FR activity in normal conditions and during spike-and-wave (SW) epilepsy seizures induced by pentylenetetrazole (PTZ) administration in three Sprague-Dawley rats. Electrocorticogram (ECoG) and intracortical (IC) field potentials were recorded from the right somatosensory hindlimb area. The power spectral density (PSD) and the mean power (MP) of the IC signals in the HFO frequency range were calculated during periods of normal brain activity (i.e. baseline) and during the induced SW activity. The results showed that the MP of FR increased by 184 % during SW compared to baseline whereas the MP of R did not change significantly. These results suggest that FR are related to seizure activity and therefore can be used as biomarkers for seizures.