Lions sleeping in a tree (Image: R. Rees)

Sleep is a confounding phenomenon: Everybody does it, but no one has a precise understanding of why we sleep or what sleep does to our brains. And to researchers in a broad variety of fields, from biologists who study sleeping flies to clinicians treating sleep disorders, the pull of sleep is irresistible.

“It’s obviously essential to life, it’s persisted across millions of years of evolution, and it’s altered in a large range of brain disorders,” says cognitive neuroscientist and psychiatrist Alex Herman at the University of Minnesota, “but we know so little about it.”

Sleep is deeply tied to learning, bodily health, brain development, and aging, but its function in the processes largely remains a mystery. It’s also inextricably tied to time, says SFI External Professor Van Savage, a mathematical biologist at UCLA. For example: “How long do you sleep? How long is REM [rapid-eye movement] sleep?” he asks.

Sleep patterns change from birth to adulthood, and, in general, people sleep less as they get older. Researchers have also observed patterns associated with organism size: Mice sleep for 16 hours per day, while blue whales, the largest animals on the planet, sleep for only 1.5.

Savage and Herman have organized a working group with invitees from a wide range of fields, all united by their interest in sleep. The working group, held November 18-20 at SFI, beginning to unpack the causes, timescales, and consequences of sleep. In particular, participants are focusing on how sleep time changes across species, and how it changes with age and during adulthood.

The working group is part of SFI’s Complex Time: Adaptation, Aging, and the Arrow of Time research theme, which looks at how adaptation and entropy play out in complex systems. The study of sleep suggests new ways to think about how biological time, represented by aging or changing sleep patterns, for example, are entangled with physical time, determined by the regular movement of Earth around the sun.

“Understanding how these multiple clocks are coupled together is very much what we mean when we talk about complex time,” says Amy P. Chen, who manages the program at SFI. But understanding those connections requires a multidisciplinary effort, she says. “We want to get the people who don’t usually talk to each other in the same room.”

The researchers’ goals for the working group include novel collaborations and, ultimately, a book in the SFI Press to collect new insights in the field. The Complex Time research theme is funded by a grant from the James S. McDonnell Foundation.