Mapping 4-AP induced epilepsy propagation with a micro-electrode array in intact hippocampus in-vitro

Epileptic seizures are a symptom of epilepsy and are transient signs or symptoms of abnormal, excessive or synchronous neuronal activity in the brain. Epilepsy is the underlying tendency of the brain to recurrent unprovoked seizures. The hippocampus is a common site of seizures and hippocampal slices have been used to study the generation and propagation of seizures. A novel penetrating microelectrode array was designed and fabricated to record activity in the hippocampal preparation in mice. Furthermore, the hippocampus contains both longitudinal and transverse pathways therefore we tested the hypothesis that propagation can take along these two orthogonal pathways. In order to map this orthogonal propagation, a micro-machined 3D array is applied to an intact hippocampus preparation incubated in artificial cerebrospinal fluid (ACSF) containing 4-AminoPyridine (4-AP). The data suggests that the 4-AP induced epileptic activity in hippocampus starts in CA3 region and propagates in transverse direction from CA3 to CA1 and in longitudinal direction of CA3 simultaneously. Therefore, a single interictal event can invade the entire hippocampus from the septal to the temporal region and from the CA3 to the CA1.