Summary

In the first half of the twentieth century, research by von Economo and Walle Nauta implicated the hypothalamus in sleep and waking. In the subsequent 50 years the hypothalamus was abandoned and instead the pons was considered to house the neurons regulating states of consciousness. In 1999, the linkage of a hypothalamic peptide, hypocretin, with narcolepsy shifted the emphasis back to the hypothalamus. However, since REM sleep originates from the pons, we sought to identify how the hypothalamus links with the pons, which would elucidate a network map of regions responsible for all three states. In this review we summarize our hypothesis that hypothalamic wake and non-REM sleep active neurons link with a group of i nhibitory pontine neurons to gate the transition to REM sleep. This hypothesis was first publically presented by us at the Society for Neuroscience meeting in 2004. We suggest that the pontine areas inhibiting REM sleep (PAIRS) represent GABA neurons; that these neurons are activated by glucosensing neurons, and neurons involved in emotion and arousal, and that their purpose is to keep the animal upright, mobile, and vigilant as it forages for food.