The neurophysiology of sleep and waking: Intracerebral connections, functioning and ascending influences of the medulla oblongata

This paper focuses on the successive historical papers related to medulla o blongata (M.O.) intracerebral connections, its activities and ascending inf luences regulating sleep-waking behavior. The M.O. certainly influences the quantitative and qualitative processes of waking, However, its neurophysiological properties are often concealed by those of the upper-situated brain stem structures. The M.O., particularly the solitary tract nucleus, is involved in sleep-ind ucing processes. This nucleus seem to act as a deactivating system of the a bove situated reticular formation, but it also impacts directly on the thal amocortical slow wave and spindle-inducing processes, The M.O. is significantly involved in paradoxical sleep mechanisms Indeed, the mesopontine executive centers are unable to induce paradoxical sleep wi thout the M.O. Moreover. stimulation of the solitary tract nucleus afferent s can induce paradoxical sleep, and the M.O. metabolic functioning is speci fically disturbed by paradoxical sleep deprivation. Finally, there seems to be a paradoxical sleep Zeitgeber. Our current knowledge shows that this lowest brain stem level is crucial fo r sleep-waking mechanisms, It will undoubtedly be further highlighted by fu ture electrophysiologial and neurochemical studies. (C) 1999 Elsevier Scien ce Ltd, All rights reserved.