Paradoxical Sleep — A Study of its Nature and Mechanisms

Abstract

This chapter discusses the results of a study that analyzes the nature and mechanisms of paradoxical sleep (P.S.), or rhombencephalic phase of sleep. In this study, both tonic and phasic electroencephalogram (EEG)or peripheral index of P.S. are very different from EEG and behavioral slow sleep. The pontine origin of rapid eye movements and of the phasic ponto-geniculo-occipital activity occurring during P.S. is emphasized. Phylogenetic study shows that slow sleep may be observed in reptiles, birds, and mammals. In contrast, P.S. is not found at all in the tortoise, and is of very short duration in birds (its ratio to the total sleep being only 0.2%). In mammals, this ratio is about 6–30%. Ontogenetic studies in the kitten show that P.S. may appear immediately after wakefulness and constitutes 90% of total sleep during the first days. In chronic pontile animals, with hypothalamic islands, the rhombencephalic phase of sleep, showing all the pontine electrical and behavioral criteria of P.S. in the intact animal, can be completely identified with the latter. Its mean duration (6 min) is analogous to that of the intact animal. No behavioral or EEG index of slow sleep was observed in pontile animals.