Wake Up! The Science of Sleep

Photo courtesy of Rebecca Carlson/AAAS

Photo courtesy of Rebecca Carlson/AAAS

Why don’t people care more about sleep? We wake up early and go to bed late, and let our kids do the same, trying to put more “day” in our days, when it’s the nights that build our memories and heal our brains and the rest of our bodies.

The National Institute of Medicine has called sleep disorders and sleep deprivation “an unmet public health problem,” Michael Twery, director of National Center on Sleep Disorders Research, told an audience at the American Association for the Advancement of Science (AAAS) in Washington, DC, on Tuesday.

Our disinterest in sleep (besides “fear of missing out”) could be lack of awareness. “It’s only been in the last ten years or so that much of this molecular information has been discovered” that connects sleep-wake disturbances (due to sleep disorder or voluntarily cutting back on sleep) to risk of a host of diseases throughout the body, including hypertension, cardiovascular disease, obesity, liver disease, and dementia. Now that we know, Twery said, what should we as a society do about it?

Dana Alliance member Clifford Saper of Harvard Medical School took us through some highlights of what scientists know about sleep. You might think sleep is the natural state, but it’s the opposite: “The brain has embedded in it a set of circuits that keep you awake; you actually have to turn them off to go to sleep,” Saper said.

“The difference between wake and sleep is like a see-saw,” he said, although the circuits spend most of their time at the ends. “We spend 98 percent of the time awake or asleep,” and only 2 percent wavering in the middle, he said. We really do “fall” asleep; Saper suggested proving this to yourself by watching drowsy people in the lecture hall (not our lecture, though!) or on the metro to see that moment of “falling.”

And that old saw I believed about older people needing less sleep isn’t true, either: “They don’t sleep less because they need less sleep, they sleep less because they can’t sleep more—and they feel like they need more sleep,” Saper said. His lab and others have found that a progressive loss of neurons in the suprachiasmatic nucleus (SCN) correlates with broken sleep patterns as we age. The SCN, which resets our 24-hour clock each day, is tiny, Saper said, “about the size of the head of a pin, but it controls everything in your life, amazingly enough.” Even your time of death has a circadian (daily) rhythm. [Some of this research is funded by a Dana grant; read more about this work in an interview with Saper.]

In addition, while we all may have the same style of clock, it may be set a little differently. Saper and his colleagues, especially Andrew Lim, have found one of the many clock genes that codes for “awake” time. People with one variation (AA) wake up an hour or two earlier than people with the opposite variant (GG); those with one gene from each variant (AG/GA) wake up right in between. “Everyone in the room has a predisposition to rise early or not,” Saper said. This variation also seems to affect time of death: “People with GG are just delayed, 6 hours,” he said.

So what are we doing while we’re sleeping, besides “flushing toxins?” Sometimes we’re dreaming. Researchers are coming around to considering that dreams “are simply thinking in another biological state,” said Deirdre Leigh Barrett, also of Harvard Medical School. “There’s lots more activity in our secondary visual area, where the higher-order visualization is, even more active than when we’re awake.” Secondary motor areas also show high activity, even as primary motor (which move our body) and external sensory (collecting data from the senses) are off-line, along with prefrontal “inhibition” areas.

Much of our dream content is focused on emotional and personal issues, but Barrett is especially interested in the less-common instances when dreams can suggest practical ideas or lead to an answer to a problem dreamers may be having in their waking state. Artists like Dali and Jasper Johns are inspired by dreams, but Barrett also described architects dreaming they were walking through as-yet-unmade buildings, “noticing” solutions to technical problems that their waking brains had not yet solved. Paul McCartney said he dreamed the melody to the Beatles tune “Yesterday;” unusual, Barrett said, since most of our dreams have strong visual content and very weak sound content. Writers, scientists, and thinkers like Gandhi have found ideas, proofs, and solutions via dreams.

Barrett conducted research with university students, seeing if dreaming brings solutions to brain-teasers and also running a study where students chose their own problem to try to solve via dreaming. In that study, half of the participants said they’d dreamed about the problem, and one-third said they solved it (knock that down to one-quarter when researchers used “objective measures” to see if it was solved). Pretty good odds for people who are looking for a breakthrough on a tough problem.

The session was part of the Neuroscience and Society series, a partnership between the Dana Foundation and AAAS. Previous sessions are available via video, including The Arts and the Brain, Neuroenhancement, and The Adolescent Brain. [update 20 March: the sleep session video is now up.] Upcoming sessions: May 6 (Taste and Smell), Sept. 18 (Stress), Oct. 28 (Illusion).

–Nicky Penttila

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