Things That Go Bump

Scientists still don’t know why animals sleep or how to define the ubiquitous behavior.

By | March 1, 2016

ANDRZEJ KRAUZEStrange things happen in the night. Distant stars flicker above darkened towns. Nocturnal creatures prowl. Things go bump. And every night (if we’re lucky), we sleep through it all. But for all its ubiquity, for all its regularity, and for all the intimacy we feel toward a phenomenon that literally lays us flat every day of our lives, sleep is mysterious. It may, in fact, be one of the broadest biological enigmas left. We’re not entirely sure how other animals sleep, or even if they all do. We don’t know why any of us sleep. We know neither exactly how sleep benefits us nor how skipping it harms us. We don’t even have a clear definition of the process.

But as with many enduring scientific mysteries, there are intrepid researchers who seek to crack sleep open and understand its intricacies. This issue celebrates them.

Like early geologists scraping through the uppermost layers of the Earth’s crust, researchers in the relatively small field of sleep science are devising methods, technologies, and experimental designs that aim to lay bare what is undoubtedly a massive trove of game-changing discoveries lurking beneath the surface. From attempts to document the circadian rhythms of humans cut off from sunlight and temperature cycles in the depths of a Kentucky cave to modern optogenetic and molecular manipulations of the brain’s sleep centers, researchers have been probing into the brains and cells of snoozing humans and nonhuman animals, hoping to gain basic insights into how and why we sleep. Other scientists have sought to pin down more-fundamental, emergent properties of sleep, inciting sleep-like behavior in isolated bits of cortical tissue and even in networks of neurons and glial cells in vitro.

Even without a solid handle on the biological functions of sleep, researchers and clinicians have been addressing sleep pathologies in patients for decades. Here, Senior Editor Kerry Grens takes a peek inside clinical sleep labs to explore the latest research on the neural, metabolic, and long-term effects of sleep disruption. And a Bio Business article by Anna Azvolinsky surveys the landscape of companies developing drugs to treat insomnia.

Some lines of inquiry are penetrating sleep’s inner sanctum—the world of dreams. If we know little about how sleep jibes with biology, we know even less about how and why the sleeping brain engages in time travel, shape shifting, and emotional animation on a nightly basis. But again, researchers are mapping the human brain’s dream centers, and at least one scientist calls for sleep and dreaming to be incorporated into models of the human mind in order to form a more complete concept of that still-amorphous entity.

As with any emerging field, sleep science raises its share of controversial questions: Is depriving an organism of sleep the best way to ferret out sleep’s function? Is it even ethical to deprive people of sleep in clinical studies, given the myriad problems that such disruption seems to evoke? How strong is the evidence that sleep plays a role in memory consolidation or learning?

There is broad concurrence on this last point, though some sleep scientists challenge the notion that sleep evolved as a means of cementing long-term memories. The epic poet Homer declared in the Odyssey, “There is a time for many words, and there is also a time for sleep.” In these pages are a very many insightful words from the front lines of science’s voyage to the heart of sleep’s terra incognita. Enjoy them all. Then, given the evidence that sleep can aid your memory and hone your learning, maybe take a nap when you’re done. 

Bob Grant  Senior Editor  Special Issue Coordinator

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Avatar of: Neurona

Neurona

Posts: 71

March 1, 2016

I thought that Nedergaard's work on the glymphatic system the past several years was a pretty good indicator of the benefit of sleep....?   Go look at "The glymphatic system: A beginner's guide" in Neurochem Res, Dec 2015. 

Avatar of: marc verhaegen

marc verhaegen

Posts: 17

March 1, 2016

Lions sleep most of the day, elephants eat most of the day (& night). Primates & birds have colour vision, hence sleep at night, but most mammals are more active at night (safer?). Possibly, originally humans had to sleep half of the day (more in winter? less in summer?), but since the invention of artificial light, we could be active at night, and possibly we are evolving to need less sleep? IOW, sleep is perhaps mostly just what it looks: a period of inactivity when the animal can best be inactive: during the day for humans, during the night for most mammals.

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