INITIATION OF SPONTANEOUS EPILEPTIFORM ACTIVITY IN THE NEOCORTICAL SLICE

Cortical local circuitry is important in epileptogenesis. Voltage-sens itive dyes and fast imaging were used to visualize the initiation of s pontaneous paroxysmal events in adult rat neocortical slices. Although spontaneous paroxysmal events could start from anywhere in the prepar ation, optical imaging revealed that all spontaneous events started at a few confined initiation foci and propagated to the whole preparatio n. Multielectrode recording over hundreds of spontaneous events reveal ed that often two or three initiation foci coexisted in each preparati on (n = 10). These foci took turns being dominant; the dominant focus initiated the majority of the spontaneous paroxysmal events during tha t period. The dominant focus and dynamic rearrangement of foci suggest that the initiation of spontaneous epileptiform events Involves a loc al multineuronal process, perhaps with potentiated synapses.