title: Early deficits in spatial memory and theta rhythm in experimental temporal lobe epilepsy.
abstract: Patients with temporal lobe epilepsy (TLE), the most common form of epilepsy in adults, often display cognitive deficits. The time course and underlying mechanisms of cognitive decline remain unknown during epileptogenesis (the process leading to epilepsy). Using the rat pilocarpine model of TLE, we performed a longitudinal study to assess spatial and nonspatial cognitive performance during epileptogenesis. In parallel, we monitored interictal-like activity (ILA) in the hippocampal CA1 region, as well as theta oscillations, a brain rhythm central to numerous cognitive processes. Here, we report that spatial memory was altered soon after pilocarpine-induced status epilepticus, i.e., already during the seizure-free, latent period. Spatial deficits correlated with a decrease in the power of theta oscillations but not with the frequency of ILA. Spatial deficits persisted when animals had spontaneous seizures (chronic stage) without further modification. In contrast, nonspatial memory performances remained unaffected throughout. We conclude that the reorganization of hippocampal circuitry that immediately follows the initial insult can affect theta oscillation mechanisms, in turn, resulting in deficits in hippocampus-dependent memory tasks. These deficits may be dissociated from the process that leads to epilepsy itself but could instead constitute, as ILA, early markers in at-risk patients and/or provide beneficial therapeutic targets.
authors.affiliation: Inserm-U751, Université de la Méditerranée, 13005 Marseille, France. laetitia.chauviere@univmed.fr
authors.forename: Laetitia
authors.initials: L
authors.lastname: Chauvière
authors.forename: Nadia
authors.initials: N
authors.lastname: Rafrafi
authors.forename: Catherine
authors.initials: C
authors.lastname: Thinus-Blanc
authors.forename: Fabrice
authors.initials: F
authors.lastname: Bartolomei
authors.forename: Monique
authors.initials: M
authors.lastname: Esclapez
authors.forename: Christophe
authors.initials: C
authors.lastname: Bernard
mesh_terms: D000818:Animals; D004833:Epilepsy, Temporal Lobe / Q000139:chemically induced / Q000503:physiopathology*; D008297:Male; D008568:Memory / Q000502:physiology*; D008569:Memory Disorders / Q000139:chemically induced / Q000503:physiopathology*; D010862:Pilocarpine / Q000633:toxicity; D051381:Rats; D017208:Rats, Wistar; D013037:Spatial Behavior / Q000187:drug effects / Q000502:physiology*; D013826:Theta Rhythm / Q000187:drug effects; D013997:Time Factors
chemical_list: D010862:Pilocarpine