The sleep switch: hypothalamic control of sleep and wakefulness

More than 70 years ago, von Economo predicted a wake-promoting area in the posterior hypothalamus and a sleep-promoting region in the preoptic area. R ecent studies have dramatically confirmed these predictions. The ventrolate ral preoptic nucleus contains GABAergic and galaninergic neurons that are a ctive during sleep and are necessary for normal sleep. The posterior latera l hypothalamus contains orexin/hypocretin neurons that are crucial for main taining normal wakefulness. A model is proposed in which wake-and sleep-pro moting neurons inhibit each other, which results in stable wakefulness and sleep. Disruption of wake-or sleep-promoting pathways results in behavioral state instability.