The Science of Sleep: How One Researcher Set Out to Change the Way We See Napping

Dr. Sara Mednick’s office is tucked away in an unobtrusive corner of the Veteran’s Administration hospital on the University of California, San Diego campus. On first inspection, it seems like any other wing of the hospital, with its twisting and turning corridors and overhead announcements. But the carpeted floors, unassuming wall plaques identifying a room as “Bedroom 1,” and a fluffy blanket draped over a wall railing are just a few hints that this wing is not what it seems. It is home to UCSD’s Laboratory of Sleep and Behavioral Neuroscience. Closer inspection of one of the “bedrooms” reveals a comfortable bed and Spartan furnishings.

“I nap here all the time,” Mednick says. “I’ve been napping through grad school. It saved my life.”

Sara has called this sleepy corner of the VA home for the past two years, and in that time, has enjoyed a level of celebrity few scientists ever achieve, making the rounds on Good Morning America, Google, as well as giving countless interviews for major news outlets, including the Washington Post, Newsweek and the New York Times in support of her book Take a Nap! Change Your Life (Workman Publishing, December 2006). When asked how she feels about the media attention, she smiles.

“That’s is something I’ve enjoyed so much, that my research is so translatable,” she says. “Everyone can talk to me about what I do and how it affects their lives. Anyway I can contribute, it’s wonderful. I love it.”

Mednick is no stranger to appearing in the public eye. A drama major as an undergraduate at Bard College, she spent a few years after graduation in Manhattan, pursuing her acting career. “After pounding the pavement everyday going to auditions, I just kind of thought, ‘Huh - I wonder if there’s something else that I can do that would use my brain a little bit because this doesn’t,'” she says.

She decided to go back to school at Harvard to work towards her doctorate in Psychology, where she began her studies on visual processing under Dr. Ken Nakayama. It was during her second year when she happened to attend a lecture for an undergraduate class given by Dr. Robert Stickgold from the Harvard Medical School.

“He was a really funny speaker and a kind of out there guy,” she says. “He had this bizarre stuff looking at nocturnal sleep and visual memory.” Recognizing his need for someone with a strong background in visual processing, she met with him and they discussed doing some work on sleep and visual learning.

“I remembered that my dad happened to be a very frequent napper,” she says, “And he still is. He’s a super big fan.” She decided that napping would be a fresh take on the same sort of sleep studies that last all night. “I’d looked at those kind of studies and thought, ‘No way am I going to sit up all night watching people sleep while I don’t get any,'” she laughs.

Beyond the technical details of sleep research, Mednick saw the problems inherent in the study of nocturnal sleep, which is borne from the nature of sleep itself. When we sleep, we pass through a number of distinct stages, broadly classed as Rapid Eye Movement (REM) sleep and Non-REM (NREM) sleep. NREM sleep consists of three different stages that are passed through, from Stage 1, also known as drowsy sleep where you are drifting off, Stage 2 sleep, where you are completely unconscious and comprises approximately half the time you spend asleep, Stage 3 or Slow Wave Sleep (SWS) is the deepest period of sleep.

“There’s some studies where they let you sleep for the first part of the night, then it’s mostly slow wave sleep and some REM, or they let you sleep for the second part of the night, and that’s mostly REM and some slow wave,” Mednick explains. “But those are not totally clean because there’s always going to be some amount of the other stages of sleep creeping in there.”

Napping for short periods of time avoids these confounding effects. Naps can be timed so that there’s only Stage 2 sleep, or Stage 2 with SWS, or one that also includes REM sleep. All this can be controlled simply by waking the person up after a certain amount of time.

To study the effect of napping on visual perception, 129 undergraduates were tested four times in a day identifying what letter, either a T or L, had been briefly flashed on the screen. The control group would simply perform the tasks without napping. The two experimental groups took either a 30 minute or a 60 minute nap between the second and third testing session, around 2PM. What she found was astonishing. Performance steadily deteriorated over the course of the day in the control group as they made more mistakes. Nappers, however, rebounded after their brief snooze. More surprisingly, the performance of the subjects who napped for an hour returned to the same levels they showed at the beginning of the day, when they were most fresh-faced and alert.

Mednick found the difference between the two different nap lengths intriguing, so she conducted a few more experiments to determine if increasing motivation could prevent the subjects from letting their performance deteriorate. It turned out that no amount of motivation improved the performance of non-nappers. Further prodding revealed that moving the target to a different part of the testing screen also abolished the deterioration observed in non-nappers, which led Mednick to believe that it had something to do with early visual processing and some area of the visual cortex was fatiguing, which was alleviated when the subject slept. The study was published in Nature Neuroscience in 2002 under the title, “The restorative effect of naps on perceptual deterioration.” In a follow-up study in 2003, also published in Nature Neuroscience, entitled "Sleep-dependent learning: a nap is as good as a night", Mednick and colleagues showed perceptual learning from a nap was similar to that of a night of sleep.

Following the completion of her PhD, Mednick found a home as a Research Fellow at the Salk Institute in the lab of Dr. Geoffrey Boynton, who was studying visual perception using function Magentic Resonance Imaging (fMRI ). fMRI exploits the change in the levels of blood oxygen in areas of the brain to reveal what regions are active.

Using the fMRI techniques she learned, she confirmed that the orientation of the target was continually stimulating orientation-specific neurons in the visual areas and causing them to decrease in activation over a period of constant stimulation, and that napping caused the activation to persist. The study was published in PNAS in 2005 under the title “The time course and specificity of visual deterioration.”

Despite her background in vision research, she discovered the consortium of sleep researchers that called La Jolla home and she moved to the VA to work with Dr. Sean Drummond in The Laboratory for Sleep and Behavioral Neuroscience.

“That was the first time I’d really gotten into sleep, as opposed to being still with vision researchers as a post-doc,” Mednick says. “It’s been really interesting to go to a different field since I didn’t go to grad school with these people, but I still feel like I’ve got this whole other thing that I can contribute to this field.”

During her time with the sleep lab, she’s further studied the effect of sleep on visual deterioration and napping, her most recent study, published in Behavioral Brain Research in May of this year, under the title, "Comparing the benefits of caffeine, naps and placebo on verbal, motor and perceptual memory," revealing that caffeine isn’t the mental pick-me-up most Americans take it to be.

Comparing the equivalent of one cup of coffee’s worth of caffeine (200mg) to a 60-90 minute nap or placebo on three different types of memory: verbal memory through word recall exercises, procedural motor skills through finger tapping sequences, and perceptual learning through shape discrimination. She found that naps improved word recall over both caffeine and placebo, caffeine significantly impaired the finger tapping exercise compared to both naps and placebo, and both naps and caffeine improved texture discrimination. Napping improved both verbal and physical memory over caffeine.

These findings are intriguing in that they suggest that improving alertness through the use of stimulants is not sufficient to improve performance. Yet one of the central nagging questions of sleep research is why we even need sleep in the first place.

“It’s a good all around question because it’s clear that animals will die if you sleep deprive them,” Mednick says, “but the reasons why we need sleep are hard to define because it feels as though we are dancing around what sleep is about.”

Chronic sleep deprivation is associated with increased risks for heart disease, mental illness, obesity and even diabetes. One theory about the function of sleep deals with the natural cycling of certain hormones involved in stress and regeneration: cortisol and growth hormone.

Cortosol is a stress hormone that is secreted by the adrenal glands and is responsible for the fight or flight response, is known to increase blood pressure and blood sugar and reduce immune responses. During periods of sleep deprivation, cortisol levels are elevated, which is linked to memory impairment and altered blood glucose levels.

Growth hormone (GH) is secreted by the pituitary gland in the brain and is responsible for muscle and bone growth, fat metabolism and immune system stimulation. It has been shown that sleep deprivation abolishes the surge of GH that is triggered by nocturnal sleep. Furthermore, misregulation of these hormones leads to misregulation of the two hormones controlling appetite, ghrellin and leptin.

“You have this super-charged daytime functioning and in order to repair from this state, you need sleep, because the stuff that goes on during sleep does not go on during wake and vice-versa,” Mednick explains.

Despite the fact that chronic sleep deprivation seems to be a way of life for most Americans, it seems like an impossibility to pull coffee away from the some odd 90% of the population that relies on the stimulant to function in the afternoons and have them opt for some shut-eye, which is due, in large part to the social stigma attached to nappers. When asked about her thoughts on this attitude, she sighs.

“It’s hard to say because it’s only really in America where it exists really strongly,” she says. “My guess is that it has to do with when Americans established themselves as separate from Europe and they wanted to give up a lot of the traditions, but they threw out the baby with the bathwater, which was just making sure you get enough sleep.”

This devaluation of sleep has become part of American culture and this ethos is particularly notorious in the military and medical professions.

“What you find is a kind of macho ego-driven thing about not needing sleep, but when studies are done on these groups, you find that they’re as infallible as everybody else and their performance does decrease,” Mednick says.

Mednick is not alone in this sentiment. An article appearing earlier this year on Slate.com by William Saletan recounts the findings of a report commissioned by the Pentagon’s office of Defense Research and Engineering called, “Human Performance,” including the effects of sleep deprivation on troop performance and the steps the military has taken using chemicals to combat this effect, ranging from caffeine to amphetamines.

A recent panel of the Institute of Medicine found that despite the efforts of the Accreditation Council for Graduate Medicine placing caps on the hours doctors can work without a break for sleep in 2003, medical residents are still sleep-deprived, partially because it’s seen as a badge of honor.

Mednick believes you need science to change the mystique that napping holds, so in 2006, she paired up with Workman Publishers to publish her book, Take a Nap! Change Your Life, aimed at removing the stigma of napping in the minds of millions of Americans and showing them how they can fit a nap into their busy schedules for maximum effectiveness.

As a result, she has been touring the country, appearing on national television and in major news outlets, espousing the benefits of napping.

“It’s very frequent where I’ll hear about a company that has a nap salon, or that there are now businesses in Manhattan where you can go pay for a nap,” she says. “There are even design companies that are making nap pods and Brookstone has a nap chair, so there are lots of different ways in which it’s become chic, in a way.”

And this is what needs to happen in order to making napping part of the social norm, she believes.

“It think Wall Street really needs it, but so do factories, truck drivers, airline pilots, people who do things that are repetitive and work long hours, like doctors,” she says. “Those are the places where there needs to be a redefinition of sleep and it’s importance.”

Mednick’s proclivity to reach out and help others through her research extends beyond her findings, however. A friend of hers, Professor Anita Hettena at San Diego City College, thought it might be fun to expose her students to the research going on in Mednick’s lab.

“Since my lab isn’t a wet lab, I thought that they would get a better sense of science if they actually volunteered as research assistants,” says Mednick. Hettena selected a group of strong students, who learned the ins and outs of working in a sleep lab.

“Since our first crop of students worked out so well, we decided to admit three students into my lab every six months,” explains Mednick. “Science is inherently interesting and fun, you just have to find the right entryway for each person.”

Among the most recent volunteers is Erin Kenney. As an undergraduate at the University of California, Santa Barbara, she didn’t have much exposure to research, and following her graduation with a Bachelors in Biological Sciences in 2006, she began taking courses at City College.

“I began taking classes for fun and to keep my memory refreshed,” Kenney says. “I took Anatomy in the fall of 2007 and became good friends with my professor, Dr. Hettena. She recommended me to Sara.”

During her time in the lab, Kenney has learned to distinguish the different stages of sleep and how sleep research is done. “This experience has definitely inspired me and sparked my interest for research and I hope to incorporate research into my life when I am a doctor,” she says.

“I feel especially excited about helping students from a variety of backgrounds find themselves interested in science,” Mednick says. “I myself had a theater background and the only reason I’m faculty at UCSD is because a couple of people took a chance and spent time training me to be a scientist.”

Mednick’s unlikely background and desire to help others makes her the ideal spokesperson for changing the world, one nap at a time. “It seems to me that a beautiful aspect of human beings is that they all will just go to sleep at some point and that there’s some point in the night where you can rest assured that there’s a great deal of people who are in bed all around you sleeping,” she says. “There’s something kind of sweet about that.”

More information about Dr. Mednick can be found at her website.

Join in the discussion about sleep research with the Sleep Science San Diego group.