Formation of the sleep-regulating mechanisms in vertebrates.

The paper presents new data concerning the mechanisms of regulation of sleep-like states in vertebrates. Somato-vegetative and behavioral correlates of primary sleep (fish, amphibians), intermediate sleep (reptiles), slow-wave and paradoxical sleep (birds) are described. The evolutionary more ancient hypothalamo-cortical and young thalamo-cortical levels of regulation of different forms of sleep are examined. Problems of existence of functional analogues of homoiotherms' sleep are discussed.