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Stanford University School of Medicine

Easing into slumber requires newly identified “sleep/wake” brain circuit… and a comfy nest

Mice do this very cute thing just before they go to sleep. They build little nests. They only build the nests when they're getting... really ... sleeeeeepy.

Think about that for a minute. Building a nest is complicated. You've got to spot the materials, gather them, figure out where to put them, assemble them into a nest ... I don't know about you, but I'm getting tired just thinking about it.

Most things are hard to do when you're sleepy. I mean, brushing my teeth, taking my contact lenses out, fluffing the pillows and turning the covers down -- I can barely pull it off before collapsing into my nocturnal sprawl.

And that's just "sleepy." Try running away from an actual predator (not one you're just dreaming about) when you're actually  sound asleep. Big nope. You can't seek food in your sleep, unless you're a talented sleepwalker who knows just which refrigerator shelf that cake slice is sitting on.

It makes intuitive sense that our reward system -- an archipelago of interconnected brain clusters that motivates goal-directed behaviors such as fleeing from predators or looking for food -- and our sleep-wake cycle would coordinate with one another.

Yet, no precise anatomical location for this integration of the mammalian brain's reward and arousal systems has ever been pinpointed.

Until now. In a new study in Nature NeuroscienceAda Eban-Rothschild, PhD, Luis de Lecea, PhD, and their fellow Stanford neuroscientists identified a brain circuit that's indispensable to the sleep-wake cycle as well as a key component of the reward system. They proved that revving up this circuit wakes lab mice up out of deep sleep, keeps them up way past their bedtimes, and does all the other things that reward-circuit stimulating drugs such as amphetamines do.

Contrariwise, down-shifting this single circuit is enough to put the mice to sleep and keep them sleeping -- even in the presence of a sexy mate, a tantalizing taste treat, or the fear-inducing aroma of fox urine. The other thing it does, curiously, is get them to build nests. Even when they're sleep-deprived, the mice can't fall asleep until they've built a nice comfy little nest to hide and stay warm in -- although if you supply them with bedding they've previously assembled into a nest, they'll climb right in, clock out, and drop off.

The study has huge clinical relevance for the 25 to 30 percent of all Americans who suffer from sleep difficulties of one sort or another. As de Lecea said when I interviewed him for our news release announcing the study's publication:

Insomnia, a multibillion-dollar market for pharmaceutical companies, has traditionally been treated with drugs such as benzodiazepines that nonspecifically shut down the entire brain. Now we see the possibility of developing therapies that, by narrowly targeting this newly identified circuit, could induce much higher-quality sleep.

In addition to flagging a new entry point for pharmacological fixes, the focus on the behavior -- nest building -- that mice find so necessary in preparing to drift off into dreamland, the discovery speaks volumes about the importance of sleep hygiene: maybe all that tooth-brushing, pillow-fluffing, cover-turning activity makes me sleepier for a reason. It's my equivalent of building a nest.

Previously: How to tell if you're sleep-deprived, From A to ZZZZs: The trouble with teen sleep and In mice, at least, uninterrupted sleep is critical for memory
Photo by Ada Eban-Rothschild

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