ABSTRACT
The first theories about the existence of specific sleep and wakefulness centers in the brain were based upon observations of hypersomnia and insomnia in patients with disorders of the central nervous system. Tro¨mner, for example, believed in the existence of a sleep center in the thalamus (1). On the other hand, Von Economo-on the base of his observations of sleep-wake disturbances following encephalitis lethargica-postulated the existence of a wakefulness-promoting area in the posterior hypothalamus and of a sleep-promoting area in the anterior thalamus (2).
