Ectopic action potential generation: its occurrence in a chronic epileptogenic focus.

Intracortical axon terminals of thalamocortical relay neurons projecting into chronic cortical epileptogenic foci may generate high frequency bursts of action potentials during spontaneous cortical epileptiform paroxysms. Such bursts occur regularly before onset of the corresponding surface paroxysms in a large proportion of the tested neurons. Therefore, such axon terminals bursting may participate in the triggering of the synchronous, prolonged intracellular depolarization shifts which are observed in cortical neurons during epileptic events.