Pre-ictal increase in theta synchrony between the hippocampus and prefrontal cortex in a rat model of temporal lobe epilepsy

Author(s)

Silveira Broggini, Ana Clara ^[1] ; Esteves, Ingrid Miranda ^[1] ; Romcy-Pereira, Rodrigo Neves ^[2] ; Leite, Joao Pereira ^[1] ; Leao, Richardson Naves ^{[2, 3]}

Affiliation

^[1] Univ Sao Paulo, Ribeirao Preto Med Sch, Dept Neurosci & Behav, Ave Bandeirantes 3900, BR-14049900 Ribeirao Preto, SP - Brazil

^[2] Univ Fed Rio Grande do Norte, Inst Brain, Ave Nascimento de Castro 2155, BR-59056450 Natal, RN - Brazil

^[3] Uppsala Univ, Dept Neurosci, Unit Dev Genet, Uppsala - Sweden

• Document type: Journal article
• Source: Experimental Neurology; v. 279, p. 232-242, MAY 2016.
• Web of Science Citations: 10

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. (C) 2016 Elsevier Inc. All rights reserved. (AU)

• FAPESP's process: 11/10898-9 - Characterization of behavior, eletrographic and molecular changes during and after spontaneous recurrent seizures in the temporal lobe epilepsy model chronic phase induced by continuous electrical perforant path stimulation
• Grantee: Ana Clara Silveira Broggini
• Support Opportunities: Scholarships in Brazil - Doctorate