Event-related non-specific responses (K-complexes) during sleep.

Abstract

EEG responses to sensory stimuli were obtained by averaging. In averages representing the reactivity of the approx. 5 min sleep period, the fluctuation of the amplitude of the obligatory part was evaluated. The deepening of sleep was reliably indicated by the increase in amplitude while the lightening of sleep by a decrease in amplitude within stage 2. In longer sleep periods beside the above tendency a micro-fluctuation occurred as evidence of the fine fluctuations of the sleep level within the phases. The synchronization response could be followed by this method even in the deep sleep stages and the above behaviour of the amplitudes of averages remained unchanged. This shows that the synchronization response to arousal stimuli is a uniform phenomenon during the whole slow-wave sleep. Our results support the assumption that the spontaneous or evoked synchronization phenomena in sleep are the products of the dynamic balance in the sleep-arousal system. An increase of amplitude may indicate an increase in the tonus of the sleep system while its decrease an opposite process. The present observations, similarly to our earlier results, may be adapted well to the sleep model based on the phasic activation and reciprocal induction theory.