[Contribution of positron emission tomography in the study of wakefulness and sleep. Status of the question].

Positron emission tomography (PET) allows the exploration of cerebral physiological and biochemical processes in vivo in man. Sleep studies using this technique first demonstrated that cerebral metabolic rates for glucose decrease during slow wave sleep in comparison with wakefulness whereas, during paradoxical sleep, the cerebral glucose metabolism is as high as during wakefulness. At present, several laboratories are currently exploring the regional modifications of cerebral blood flow during sleep. The results are partial and preliminary but seem to show a relative decrease in frontal cortex blood flow during slow sleep. This short review also considers some PET studies of sleep deprivation and sleep related pathologies.