Behavioral and spectral electroencephalographic biomarkers of epileptogenesis, disease progression, and drug resistance in a longitudinal lithium-pilocarpine model of temporal lobe epilepsy

Temporal lobe epilepsy (TLE) is linked to progressive alterations in brain network dynamics, leading to behavioral comorbidities and emergence of drug resistance; yet the underlying mechanistic and synaptic substrates remain incompletely understood. Here, we performed longitudinal phase-specific characterization of network dysfunction in TLE employing a lithium-pilocarpine-induced model in 7-week male Wistar rats. We integrated behavioral and electroencephalographic (EEG) analyses at five timepoints: baseline, acute, latent, chronic phases, and after assessment of drug-resistant epilepsy (DRE). After the chronic phase, responsiveness to phenobarbital (PB), a standardized approach for DRE characterization, was assessed via video monitoring to identify drug-resistant (DRUG-R) and drug-sensitive (DRUG-S) subpopulations. Our data show that epileptic rats exhibited progressive and phase-dependent behavioral and EEG alterations. Behavioral profiling revealed a hypermotor phenotype, impairment in burrowing natural behavior, altered phase-specific response to anxiety and depressive-associated behavioral paradigms, and progressive memory impairment. Following PB treatment, the identified DRUG-R subpopulation displayed specific hyperactive behavioral traits compared with DRUG-S, especially in anxiety-associated and burrowing behaviors. Spectral EEG analysis revealed modulation of frequency bands across disease stages, particularly in Theta and Delta power, and descriptive analyses attempted to stratify animals based on different responsiveness to PB. Lastly, correlation analyses supported associations between EEG, frequency of seizures and behavioral measures, especially in the anxiety domain and declarative memory. This study, moving beyond a seizure-centric perspective, evidences that TLE induces progressive and phase-specific reorganization of cortical activity that relapse on distinct electrophysiological and behavioral features, offering a novel framework to identify translational stage-related signatures of epileptogenesis and DRE.