Envelope analysis as a tool for identifying epileptic EEG patterns during the sleep-wake cycle in rats

BackgroundThis research aimed to study electroencephalographic abnormalities in an animal model of temporal lobe epilepsy induced by pilocarpine. By using the coefficient of variation of the envelope (CVE) of electroencephalography (EEG), we characterize and quantify morphological alterations in sleep-wake cycle (SWC) stages. MethodsEpilepsy was induced in 13 rats using a single dose of intraperitoneal pilocarpine injection. A second group of 13 rats served as the control. All the rats underwent polysomnography for at least two days. To do so, three channels were created using four electrodes for EEG and one more for EMG. Channels were built using contralateral lead. ResultsEnvelope analysis revealed global alterations in EEG morphology. Significant differences were observed in the delta and theta bands between the epileptic and control groups. Epileptic animals showed a near-total suppression of theta rhythm activity during REM sleep. Additionally, we identified a novel pattern of synchronized slow waves (sDelta), distinct from the physiological delta waves observed in non-REM sleep. ConclusionIdentifying both subtle and overt morphological abnormalities in EEG is challenging for human experts and computational methods. By applying CVE analysis to the well-known pilocarpine model, we reveal abnormal EEG dynamics with exceptional summarizing capabilities. For example, a 24-hour EEG can be synthesized into a single, easily interpretable visualization of EEG morphology. This technique and its underlying framework may serve as valuable tools for epilepsy research and potential diagnostic applications.