TONIC INFLUENCE OF NEOCORTEX ON HIPPOCAMPAL SEIZURES

The interaction between different brain structures could be crucial to predicting seizure occurrence, threshold and spread. Moreover, the sleep-wake cycle and electrical activity of brain structures in different phases of sleep could significantly affect the pattern and extent of seizure spread, and therefore the characteristics of epileptic activity. In this animal model using 15 Wistar rats, we show that the duration of hippocampal seizures, induced by electrical stimulation of the hippocampus, is significantly increased during slow sleep. Moreover, decreasing the electrical activity of the neocortex by cooling of the cortical surface or induction of cortical spreading depression also caused an increase in hippocampal seizure duration. Conversely, warming the cortical surface triggered a remission in spreading depression, in turn restoring the duration of epileptic episodes. Our data suggest that the neocortex probably exerts a tonic inhibitory influence on hippocampal seizures. Thus, cortico-hippocampal interaction could be an important component in the manifestation and generalization of limbic seizures.