Ren, S. et al. Science 362, 429–434 (2018)

How does your brain actually wake you up? It’s been a mystery, but new research in mice suggests the thalamus has something to do with it.

In humans, injuries to the thalamus can result in comas. So the research team started by looking at neuronal activity in the thalamus of mice as they slept and woke normally. They observed that neurons in the paraventricular region of the thalamus were more active than others while the animals were awake. Activity in those neurons declined as the mice transitioned into sleep, and increased as they started to wake up. When the researchers inhibited those neurons, the mice became and stayed sleepy; when they activated them, the mice woke up.