Propagation of seizure activity in kindled dogs

The problem of determining the location of epileptogenic foci has been studied by means of a new analysis technique, the AAMI method. This AAMI method is a generalization of the more conventional cross-correlation technique, and can be used for the determination of relationships and of time delays between simultaneously recorded EEG signals during an epileptic paroxysm. Unlike the cross-correlation function, the AAMI method is not restricted to the study of linear propagation channels. The spread of seizure activity in several seizures of 3 dogs, made epileptic by the kindling process, has been analyzed, using depth recording. The focus was located in the prepyriform cortex (PPC). The spread of activity from there to the amygdala was observed. It was found that seizures can be divided into 3 phases. In the first phase (lasting up to 5 sec after the kindling stimulus) no relationship between PPC and amygdala was found. In the second phase (5-13 sec) a strong relationship between these areas was found, with consistent delay times which decreased during this interval from 19.1 to 23.6 msec at the beginning to 11.3 to 16.0 msec at the end of the interval. In the third phase of the seizures (after about 13 sec post kindling) activity in the reported areas was found to be independent again. A possible neurophysiological interpretation of these findings is given.