title: Evolution of temporal and spectral dynamics of pathologic high-frequency oscillations (pHFOs) during epileptogenesis.
abstract: OBJECTIVE
  In temporal lobe epilepsy (TLE), pathologic high frequency oscillations (pHFOs, 200-600 Hz) are present in the hippocampus, especially the dentate gyrus (DG). The pHFOs emerge during a latent period prior to the onset of spontaneous generalized seizures. We used a unilateral suprahippocampal injection of kainic acid (KA) mouse model of TLE to characterize the properties of hippocampal pHFOs during epileptogenesis.
  
  
  METHODS
  In awake head-fixed mice, 4-14 days after KA-induced status epilepticus (SE), we recorded local field potentials (LFPs) with 64-channel silicon probes spanning from CA1 alveus to the DG hilus, or with glass pipettes in the DC mode in the CA1 str radiatum.
  
  
  RESULTS
  The pHFOs, are observed simultaneously in the CA1 and the DG, or in the DG alone, as early as 4 days post-SE. The pHFOs ride on top of DC deflections, occur during motionless periods, persist through the onset of TLE, and are generated in bursts. Burst parameters remain remarkably constant during epileptogenesis, with a random number of pHFOs generated per burst. In contrast, pHFO duration and spectral dynamics evolve from short events at 4 days post-SE to prolonged discharges with complex spectral characteristics by 14 days post-SE. Simultaneous dural EEG recordings were exceedingly unreliable for detecting hippocampal pHFOs; therefore, such recordings may deceptively indicate a "silent" period even when massive hippocampal activity is present.
  
  
  CONCLUSIONS
  Our results demonstrate that hippocampal pHFOs exhibit a dynamic evolution during the epileptogenic period following SE, consistent with their role in transitioning to the chronic stage of TLE.
authors.affiliation: Department of Neurobiology Graduate Program, The David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, U.S.A.
authors.forename: Ryan T
authors.initials: RT
authors.lastname: Jones
authors.affiliation: Department of Neurology, The David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, U.S.A.
authors.forename: Albert M
authors.initials: AM
authors.lastname: Barth
authors.affiliation: Department of Neurology, The David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, U.S.A.
authors.forename: Laurel D
authors.initials: LD
authors.lastname: Ormiston
authors.affiliation: Department of Neurology, The David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, U.S.A.|Department of Physiology, The David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, U.S.A.
authors.forename: Istvan
authors.initials: I
authors.lastname: Mody
mesh_terms: D000818:Animals; D056547:CA1 Region, Hippocampal / Q000187:drug effects / Q000503:physiopathology; D003292:Convulsants / Q000494:pharmacology; D018891:Dentate Gyrus / Q000503:physiopathology; D004195:Disease Models, Animal; D004569:Electroencephalography; D004833:Epilepsy, Temporal Lobe / Q000139:chemically induced / Q000209:etiology* / Q000503:physiopathology; D006624:Hippocampus / Q000187:drug effects / Q000503:physiopathology; D007608:Kainic Acid / Q000494:pharmacology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D013226:Status Epilepticus / Q000139:chemically induced / Q000503:physiopathology
chemical_list: D003292:Convulsants; D007608:Kainic Acid
keywords: CA1; Dentate gyrus; Epileptogenesis; Kainic acid; Latent period; Pathologic high-frequency oscillations; Temporal lobe epilepsy