On Thursday, celebrity groundhog Punxsutawney Phil will emerge from his hibernation burrow and report how much longer this year’s cold weather will last. If he sees his shadow and goes back to sleep, we’ll supposedly endure six more weeks of winter. If not, we should expect an early spring.
Few animals get pulled out of slumber to make public pronouncements, but scientific data suggests that all animals probably do sleep—including the most unexpected creatures, such as fish, birds, worms, and flies. Sara Aton (B.S. ’01) can attest to dozing cats, mice, and even cuttlefish, all of which she’s studied as they snoozed. She marvels that biologists once thought bugs and birds and worms never slept.
“I think there’s this pervasive misconception that your brain is just turning off when you go to sleep, because there’s no obvious output. Outside of a coma, you can’t think of a less interesting behavior to study than sleep, right?” Aton says. “Sleep is something that, as humans, we spend a third of our life doing. And yet biologists and the neuroscience community didn’t have a lot of interest in it.”
But now that we know better, new questions arise: Do animals all rest for the same reasons?
After studying sleep for the past decade, Aton is convinced that it matters—a lot. “I’m much more protective of, for example, my son’s sleep than I would have been had I not been in this field,” she says.
In Your Dreams
Of course animals need sleep. They die without it—their organs and immune systems simply shut down. And recent tools such as brain imaging show that some parts of the brain are actually more active during sleep than during wakefulness. “The brain is clearly doing something during sleep,” Aton says. The big question is: What?
Aton has found that sleep is critical for learning new things. When new memories form, the brain changes the structure and function of its neural circuits. Disrupting sleep disrupts those essential brain changes, which matters because sleep actually helps the brain absorb new experiences. For example, people studying new vocabulary words retain the information much better if they sleep within three hours of learning; if they delay sleep, they’ll do worse on the vocab quiz. And baby chickens must sleep in the first few hours after learning to bond with their parent, or else that bond doesn’t form.
“You need sleep in a certain window of time, along with activity in a particular part of the brain and protein synthesis in that circuit,” Aton says. “It’s kind of like playing the game of Clue—for certain types of memory and certain animal models, we know what the circuit is and what tools are needed, in terms of brain activity and protein synthesis. What we’re trying to do in the lab is link those things together.”
Aton began her science career as a U-M undergraduate. While a biopsychology and cognitive science major, she conducted research, received an LSA merit award, and graduated with highest distinction. She returned in 2012 as an assistant professor in the Department of Molecular, Cellular, and Developmental Biology (MCDB), where her lab focuses on how sleep affects brain activity and physiology, such as changes in brain waves, hormones, proteins, and genes.
Neurological disorders such as Alzheimer’s disease, autism, schizophrenia, and dementia often occur in people who don’t get enough sleep. What’s still unclear is whether those disorders cause irregular sleep, or whether irregular sleep causes those disorders. Modern techniques in brain imaging and a tool called optogenetics, which makes possible the experimental manipulation of individual neurons, can help researchers understand sleep as a factor in these disorders and potentially find a treatment.
By using a technique called optogenetics, Aton and her students can see exactly how neurons signal in a mouse brain as it sleeps. The researchers also tag individual neurons in the mouse’s brain and aim lasers at the light-sensitive tags to turn neurons on or off. “We can change the pattern of activity without changing the rest of the animal’s brain state,” Aton explains, even as the mouse sleeps, and keep track of how fiddling with the neurons affects the mouse’s natural brain patterns. “Because we record and stimulate neural patterns at the same time, we can see how neurons signal to each other, how the signals change, and why or if those changes matter.”
In one experiment, graduate student Nicolette Ognjanovski and undergraduate Nora Lashner (B.S. ’14) recorded brain patterns in sleeping mice after the mice had learned something new. They teamed up with LSA Professor Michal Zochowski, who works in the departments of physics and biophysics, and then-physics graduate student Dan Maruyama (Ph.D. ’15) to get a sense of how the neurons in the mouse’s sleeping brain signaled to one another over time.
The team found that the brain patterns showed new stable signals right after mice learned something. Those same patterns recurred later on when the mice expressed the new behavior. But disrupting a mouse’s normal sleep destabilized those brain patterns and interfered with the mouse’s ability to recall what it learned.
By identifying the cellular mechanisms that boost learning and memory in a mouse brain—in other words, linking the room, weapon, and suspect in a game of Clue—Aton may uncover some clever chemistry or potential pharmaceutical that could restore memory formation and brain function in those who don’t get enough sleep.
“I love this about the University,” Aton says. “People are happy to help each other out and collaborate. Students come from completely different backgrounds, speaking completely different languages, but are willing to bridge that gap and get interested in each others’ research—without their excitement, these studies never would’ve happened.”
Sleep on It
You know sleep is important when professional football teams start handing players sleep monitors to improve their game. New England Patriot and former Wolverine Tom Brady (B.S. 1999) hits the hay at 8:30 every night to maintain his performance. But, Aton says, “If you asked an undergraduate whether they would do better on an exam if they pulled an all-nighter, I’m pretty sure that most of them would say that’s the way to go. A lot of people think they’re better off spending that time awake, trying to learn more material or rehearsing the information.”
Aton takes care to note that observations of study animals may not translate directly to humans, and she worries sometimes about hyped-up products that claim to replace the inconvenience of sleep while providing all of its benefits. But she also says that, while most research agrees that sleep leads to learning and long-term memory, sleep may not be absolutely necessary for those processes to happen in the brain. She hopes to break down which aspects of sleep are necessary for memory formation the brain, and which aspects of sleep are sufficient to achieve the same thing.
If Punxsutawney Phil sees his shadow this week and sleeps through more than another month of winter, don’t despair! Maybe he’s just improving his cognitive abilities for the coming spring. And maybe you can, too.
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