Abstracts

RATIONALE: Seizures have long been considered to be a pathological increase in correlation of neuronal activity, but there have bee few studies where the interaction between pairs of neurons were measured during seizures. We employed dual simultaneous intracellular recordings from CA1 pyramidal cells to study the interactions that develop in an In Vitro model of seizures.
METHODS: We recorded from pairs of neurons in CA1 region of rat hippocampus bathed in 4-aminopyradine (4-AP) using whole cell attached patch clamp recording technique while simultaneously recording the population activity extracellularly. Synchrony between the neurons was measured using cross correlation, phase correlation and mutual information.
RESULTS: Interictally a moderate degree of synchrony between neurons was observed. No change in synchrony prior to the onset of the seizures was detected. No prediction of an impending seizure was possible based on synchrony. During seizures the synchrony between neurons decreased. The level of synchronization normalized as the seizures abated.
CONCLUSIONS: The findings of a decrease rather than an increase in interaction during these seizures is an experimental confirmation of theoretical work where computational models have shown that desynchronous activity may be necessary for sustaining high levels of population activity. This decrease in synchrony may explain why seizures are more sustained than interictal bursts. Our findings are consistent with experimental observations that synchronous CA3 activity, or periodic electrical pacing, may suppress CA1 seizures through an increase in synchronization.
Support: NIH 7K02MH01493, 2R01MH50006, F31MH12421