Abstract
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. 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. 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. 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.
Highlights
There is increasing evidence that the brain generates electromagnetic signals over a very wide frequency range
We studied the acute and chronic phases to investigate dynamic changes in spectral power of high frequency oscillations (HFOs) at different stages of epileptogenesis, so as to provide a theoretical basis for further quantification of epileptic activity
Normal HFOs gradually mature with brain maturational processes [28]
Summary
There is increasing evidence that the brain generates electromagnetic signals over a very wide frequency range. Median frequency brain signals (MFBS) in a frequency range of 1–70 Hz are currently used in clinical practice [4]. One of the major clinical applications of measuring brain electromagnetic signals is diagnosis of epilepsy. Epileptic spikes (14–70 Hz) recorded by electroencephalography (EEG) are the hallmark for diagnosis [5, 6]. Not every epilepsy patient has spikes during an EEG recording. Researchers have been investigating new epilepsy biomarkers [7, 8]. Recent reports have shown that HFBS show promise as new biomarkers for epilepsy [8, 9]. HFBS may play a key role in epileptogenesis and epileptogenicity [12]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
