title: Pre-ictal increase in theta synchrony between the hippocampus and prefrontal cortex in a rat model of temporal lobe epilepsy.
abstract: The pathologically synchronized neuronal activity in temporal lobe epilepsy (TLE) can be triggered by network events that were once normal. Under normal conditions, hippocampus and medial prefrontal cortex (mPFC) work in synchrony during a variety of cognitive states. Abnormal changes in this circuit may aid to seizure onset and also help to explain the high association of TLE with mood disorders. We used a TLE rat model generated by perforant path (PP) stimulation to understand whether synchrony between dorsal hippocampal and mPFC networks is altered shortly before a seizure episode. We recorded hippocampal and mPFC local field potentials (LFPs) of animals with spontaneous recurrent seizures (SRSs) to verify the connectivity between these regions. We showed that SRSs decrease hippocampal theta oscillations whereas coherence in theta increases over time prior to seizure onset. This increase in synchrony is accompanied by a stronger coupling between hippocampal theta and mPFC gamma oscillation. Finally, using Granger causality we showed that hippocampus/mPFC synchrony increases in the pre-ictal phase and this increase is likely to be caused by hippocampal networks. The dorsal hippocampus is not directly connected to the mPFC; however, the functional coupling in theta between these two structures rises pre-ictally. Our data indicates that the increase in synchrony between dorsal hippocampus and mPFC may be predictive of seizures and may help to elucidate the network mechanisms that lead to seizure generation.
authors.affiliation: Department of Neurosciences and Behavior, Ribeirao Preto Medical School, University of Sao Paulo (USP), Av Bandeirantes 3900, CEP 14049-900 Ribeirao Preto, SP, Brazil. Electronic address: anaclarabroggini@usp.br.
authors.forename: Ana Clara Silveira
authors.initials: ACS
authors.lastname: Broggini
authors.affiliation: Department of Neurosciences and Behavior, Ribeirao Preto Medical School, University of Sao Paulo (USP), Av Bandeirantes 3900, CEP 14049-900 Ribeirao Preto, SP, Brazil.
authors.forename: Ingrid Miranda
authors.initials: IM
authors.lastname: Esteves
authors.affiliation: Brain Institute, Federal University of Rio Grande do Norte, Av. Nascimento de Castro 2155, 59056-450 Natal, RN, Brazil.
authors.forename: Rodrigo Neves
authors.initials: RN
authors.lastname: Romcy-Pereira
authors.affiliation: Department of Neurosciences and Behavior, Ribeirao Preto Medical School, University of Sao Paulo (USP), Av Bandeirantes 3900, CEP 14049-900 Ribeirao Preto, SP, Brazil.
authors.forename: João Pereira
authors.initials: JP
authors.lastname: Leite
authors.affiliation: Brain Institute, Federal University of Rio Grande do Norte, Av. Nascimento de Castro 2155, 59056-450 Natal, RN, Brazil; Unit of Developmental Genetics, Department of Neuroscience, Uppsala University, Uppsala, Sweden.
authors.forename: Richardson Naves
authors.initials: RN
authors.lastname: Leão
mesh_terms: D000818:Animals; D003344:Cortical Synchronization; D004558:Electric Stimulation; D004567:Electrodes, Implanted; D004569:Electroencephalography; D004833:Epilepsy, Temporal Lobe / Q000503:physiopathology*; D005071:Evoked Potentials / Q000187:drug effects; D006624:Hippocampus / Q000503:physiopathology*; D008297:Male; D009415:Nerve Net / Q000503:physiopathology; D017397:Prefrontal Cortex / Q000503:physiopathology*; D051381:Rats; D017208:Rats, Wistar; D012008:Recurrence; D013826:Theta Rhythm
keywords: Ictal patterns; Neurophysiology; Perforant path electrical stimulation; Temporal lobe epilepsy; Theta synchrony