Feline amygdaloid kindling and the sleep-waking pattern: observations on daily 22-hour polygraphic recording

For 22 h daily, polygraphic examination was made of sleep organization in four cats, both before and after amygdaloid (AM) kindling. After the completion of AM kindling and repetitive induction of kindled convulsion, the percentage of time spent in rapid eye movement sleep (REMS) significantly decreased, while the total sleep time (TST) remained unchanged. REMS suppression was most profound during the immediate postictal hours and continued through the 22-h period without a rebound increase. Slow wave sleep (SWS) was also suppressed during the postictal hours; however, this suppression was exceeded by that of REMS and was followed by a rebound increase. These changes in sleep organization were transient. During a rest interval of 2 months without kindled convulsions, they gradually disappeared and there was a complete recovery to the prekindling baseline. However, when the AM-kindled convulsion was reintroduced, there was an abrupt REMS suppression without TST change. We conclude that changes in sleep organization after AM kindling are (a) characterized by suppression of REMS and a compensatory increase in SWS, and (b) a direct but transient correlate of convulsion rather than of an acquired seizure susceptibility.