Cells of a common developmental origin regulate REM/non-REM sleep and wakefulness in mice

Neurons that regulate sleep stages Just what sleep is for remains a bit of a mystery. During sleep, we switch several times between so-called rapid eye movement (REM) and non-REM sleep. Hayashi et al. used sophisticated developmental cell fate mapping to look at the neurons involved in the two types of sleep in mice (see the Perspective by Vyazovskiy). They identified a genetically marked population of neurons that promote non-REM sleep at the expense of REM sleep. Science , this issue p. 957 ; see also p. 909