Neuronal activities in human epileptic foci and surrounding areas.

1. Extracellular microelectrode recording was carried out in human epileptogenic cortex and in the area surrounding the focus in three cases and in the hippocampus of two cases. 2. It was impossible to identify primary "epileptic" or "pacemaker" neurons. Emphasis is placed on the interactions among the neuronal aggregates at the focus for generating the epileptic discharges in the interictal stage. The possibility of plasticity in each neuronal element in the epileptogenicity is considered. Surround inhibition was not observed. The slow wave burst was accompanied by a long repetitive rhythymic burst of unitary discharge. It was shown that the slow wave burst was a modified feature of epileptic activity. 3. Various types of activity of hippocampal neurons are described, which are, however, considered as normal discharges of those neurons.