title: Dynamic Changes in Spectral and Spatial Signatures of High Frequency Oscillations in Rat Hippocampi during Epileptogenesis in Acute and Chronic Stages.
abstract: OBJECTIVE
  To analyze spectral and spatial signatures of high frequency oscillations (HFOs), which include ripples and fast ripples (FRs, >200 Hz) by quantitatively assessing average and peak spectral power in a rat model of different stages of epileptogenesis.
  
  
  METHODS
  The lithium-pilocarpine model of temporal lobe epilepsy was used. The acute phase of epilepsy was assessed by recording intracranial electroencephalography (EEG) activity for 1 day after status epilepticus (SE). The chronic phase of epilepsy, including spontaneous recurrent seizures (SRSs), was assessed by recording EEG activity for 28 days after SE. Average and peak spectral power of five frequency bands of EEG signals in CA1, CA3, and DG regions of the hippocampus were analyzed with wavelet and digital filter.
  
  
  RESULTS
  FRs occurred in the hippocampus in the animal model. Significant dynamic changes in the spectral power of FRS were identified in CA1 and CA3. The average spectral power of ripples increased at 20 min before SE (p< 0.05), peaked at 10 min before diazepam injection. It decreased at 10 min after diazepam (p< 0.05) and returned to baseline after 1 h. The average spectral power of FRs increased at 30 min before SE (p< 0.05) and peaked at 10 min before diazepam. It decreased at 10 min after diazepam (p< 0.05) and returned to baseline at 2 h after injection. The dynamic changes were similar between average and peak spectral power of FRs. Average and peak spectral power of both ripples and FRs in the chronic phase showed a gradual downward trend compared with normal rats 14 days after SE.
  
  
  CONCLUSIONS
  The spectral power of HFOs may be utilized to distinguish between normal and pathologic HFOs. Ictal average and peak spectral power of FRs were two parameters for predicting acute epileptic seizures, which could be used as a new quantitative biomarker and early warning marker of seizure. Changes in interictal HFOs power in the hippocampus at the chronic stage may be not related to seizure occurrence.
authors.affiliation: Department of Neurology, Children's Hospital of Chongqing Medical University, Chongqing, China; Ministry of Education Key Laboratory of Child Development and Disorders, Chongqing, China; Chongqing Key Laboratory of Pediatrics, Chongqing, China; China International Science and Technology Cooperation Base of Child Development and Critical Disorders, Chongqing, China.
authors.forename: Pan-Pan
authors.initials: PP
authors.lastname: Song
authors.affiliation: Department of Neurology, MEG Center, Cincinnati Children's Hospital Medical Center , Cincinnati, OH , USA.
authors.forename: Jing
authors.initials: J
authors.lastname: Xiang
authors.affiliation: Department of Neurology, Children's Hospital of Chongqing Medical University, Chongqing, China; Ministry of Education Key Laboratory of Child Development and Disorders, Chongqing, China; Chongqing Key Laboratory of Pediatrics, Chongqing, China; China International Science and Technology Cooperation Base of Child Development and Critical Disorders, Chongqing, China.
authors.forename: Li
authors.initials: L
authors.lastname: Jiang
authors.affiliation: Department of Neurology, Children's Hospital of Chongqing Medical University, Chongqing, China; Ministry of Education Key Laboratory of Child Development and Disorders, Chongqing, China; Chongqing Key Laboratory of Pediatrics, Chongqing, China; China International Science and Technology Cooperation Base of Child Development and Critical Disorders, Chongqing, China.
authors.forename: Heng-Sheng
authors.initials: HS
authors.lastname: Chen
authors.affiliation: Department of Neurology, Children's Hospital of Chongqing Medical University, Chongqing, China; Ministry of Education Key Laboratory of Child Development and Disorders, Chongqing, China; Chongqing Key Laboratory of Pediatrics, Chongqing, China; China International Science and Technology Cooperation Base of Child Development and Critical Disorders, Chongqing, China.
authors.forename: Ben-Ke
authors.initials: BK
authors.lastname: Liu
authors.affiliation: Department of Neurology, Children's Hospital of Chongqing Medical University, Chongqing, China; Ministry of Education Key Laboratory of Child Development and Disorders, Chongqing, China; Chongqing Key Laboratory of Pediatrics, Chongqing, China; China International Science and Technology Cooperation Base of Child Development and Critical Disorders, Chongqing, China.
authors.forename: Yue
authors.initials: Y
authors.lastname: Hu
keywords: epileptogenesis; high frequency oscillations; qualitative analysis; quantitative analysis; spectral power