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The faces of sleep loss (Includes interview)

Now researchers at the UC Berkeley have given us something else to stay up at night worrying about. Sleep loss can wreak such havoc in our brains that we lose our ability to correctly read the expressions on other people’s faces. If you want to become paranoid, going without sleep for a day or two is a good way to do it.
The new study was conducted on 18 healthy young adults. The researchers let them get a good night’s sleep and then presented them with images of 70 different facial expressions ranging from friendly to threatening with several neutral ones thrown into the mix. In the second part of the study, they kept the subjects up for 24 hours and showed them the same images. As the subjects viewed the images, the researchers scanned their brains and measured their heart rates. The findings, published in the Journal of Neuroscience, were troubling, to say the least.

Deprived of sleep, the participants were far more likely to interpret the expressions — even the friendly ones — as threatening. That suggested that they wouldn’t be able to discriminate between a person who poses a threat from one who does not. Similarly, severe sleep loss appears to impair our capacity to discern pain and suffering in other people’s faces. “Recognizing the emotional expressions of someone else changes everything about whether or not you decide to interact with them, and in return, whether they interact with you,” says Professor Matthew Walker, lead author of the study. “Insufficient sleep removes the rose tint to our emotional world, causing an overestimation of threat. This may explain why people who report getting too little sleep are less social and more lonely.”

“We knew that sleep shapes our emotions. We knew that it alters the way people respond to emotional states,” says Andrea Goldstein -Piekarski, lead author of the study. Previous studies had measured the responses of sleep-deprived people when, for instance, they were given gruesome pictures to view. “But we didn’t know very much about the effect sleep deprivation would have on social relations.”

To find out what exactly was happening in the brain to produce such dramatic effects, the researchers examined brain scans captured by functional Magnetic Resonance Imaging (fMRI). They discovered that two regions of the brain dedicated to sensing emotions — the anterior insula and anterior cingulate cortex — had been effectively taken offline as a result of sleep deficit. “Under normal conditions these regions can respond to threats when there is actually a threat,” Goldstein -Piekarski says, “but in sleep deprivation these brain regions can no longer make the distinction – the system breaks down.” The adverse impact isn’t confined to the brain, either. We all know that when confronted by a threat, our bodies go into overdrive — the famous fight or flight response — that sends adrenaline coursing through our bloodstream and speeds up our heart rate. But in sleep deprivation “the heart can no longer tell the difference” between a real threat and a nonthreatening situation, “and so it beats faster all the time. “ Normally, there’s ongoing communication between the brain and the heart, but in sleep loss, the two systems are “no longer correlated.” The feedback mechanism breaks down. “Sleep deprivation appears to dislocate the body from the brain,” says Walker. “You can’t follow your heart.” You can’t even hear what it’s saying. The degradation of the connection between the central and peripheral emotion-signaling systems, as they’re known, makes it difficult, if not impossible to interpret the environment or respond appropriately to social cues. Keep in mind that it only took one night of sleep loss to produce such an effect.

A good night’s sleep is an elusive goal for two-thirds of the population of the developed world, according to Walker. The Centers for Disease Control found that in the U.S., more than one out of three adults get less than seven hours of sleep a night. Although there was no significant difference between the sexes, the unemployed, the disabled and homemakers tended to experience poorer sleep than those who were regularly employed.

The subjects of the Berkeley study were deprived of 24 hours of sleep. But what about people who spend five or six hours tossing and turning with intermittent periods of sleep or those who lie awake for hours and then doze off for a few hours before the alarm goes off? The researchers couldn’t say for certain, but Goldstein-Piekarski guesses the effect would probably be more modest; our capacity to interpret facial expressions might be blunted rather than shut down altogether. But then not all sleep is equal in terms of quality, Goldstein-Piekarski points out. A person who works the night shift and sleeps seven hours during the day doesn’t derive nearly the same benefit as someone who sleeps seven hours at night. However, going sleepless for long periods of time is commonplace for many people — caffeinated students cramming for exams, police, firefighters, emergency room medical staff and military personnel — “and they’re the people we depend on most.” In 1989, New York City issued a regulation forbidding residents in city hospitals to work more than 80 hours a week or more than 24 hours at a stretch. The Berkeley findings suggest that even these restrictions may not be adequate.

The Berkeley study only lends further weight to evidence for the importance of Rapid Eye Movement (REM) or dream sleep. When the Berkeley researchers examined the brain activity of their subjects during a normal night’s sleep they discovered that their quality of their REM sleep correlated with their ability to accurately interpret facial expressions. The more dream sleep they had the better they proved to be at discriminating between threatening and friendly faces. That may explain why when dream sleep patterns are disrupted — say, by watching TV or by consuming alcohol right before you go to bed — you don’t obtain the same benefit no matter how many hours you sleep. (The National Sleep Poll –yes, there is such a thing – conducted by the National Sleep Foundation found that a staggering 95% of respondents used some kind of electric device before bedtime.)

REM sleep has also been found to reduce neurochemicals related to stress and can take the edge off traumatic memories. Goldstein -Piekarski admits that so far sleep researchers have yet to find out why REM sleep is so vital to mental and physical health. “We can ask people how well they slept the next morning, but it’s difficult to form a neurochemical picture of what’s going on in the brains while they sleep.” And while you can perform experiments on animals that might reveal more about chemical activity in the brain, “you can’t easily ask them how well they slept during the night.” Walker suggests that dream sleep may “reset the magnetic north of our emotional compass,” although more research will be needed to confirm his hypothesis.

“What’s great about sleep research is that everybody can relate to it,” says Goldstein-Piekarski, now a postdoctoral fellow at Stanford University. “Everybody knows what it’s like to have a good night’s sleep and what it’s like not to get enough sleep.”

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