by Carolyn Lacey , 29 July 2015.
Ever stay up too late and wake up thinking the world is out to get you? We cover a new study that shows that sleeping and dreaming helps you read other people better. Skipping just one night of sleep makes your brain read threat in friendly faces; while in contrast, bigger dreams make for better reality.
It’s the morning after the night before. You made an error in judgment and watched one more episode of Orange is the New Black, played another game of Monopoly, read another chapter of that book you just can’t put down, or surveyed your favorite social media site. And suddenly you are commuting to work after not enough sleep and you cannot do anything right. The coffee stand guy was rude. Your fellow commuter on the train is annoyed that you sat too close. The person you are walking behind keeps staring at you. The guy next to you at the red light keeps glaring at you. You are just feeling completely on edge and like the entire world is against you.
Well. Maybe they aren’t annoyed at you at all. Maybe you are just reading their faces wrong.
That’s the premise of the new study that came out this month in Journal of Neuroscience. The study, led by Andrea Goldstein-Piekarski in Matthew Walker’s lab at University of California, Berkeley, USA, suggests that lack of sleep turns friends into enemies.
Reading facial expressions is extremely important for how we interact with other people. And it turns out that sleeping and dreaming is essential to this ability. Goldstein-Piekarski and team found that: 1) Skipping sleep makes your brain more likely to interpret threat in faces; 2) Better quality dream sleep makes your brain better at reading faces.
Skipping a night of sleep changes how you read faces
Sleep is fundamental to our existence. Without sleep we don’t function optimally and lack of sleep wreaks havoc on general health and your brain. You are probably aware of some of the problems skipping a night or two of sleep causes to your body and your mind. Apart from that general feeling of sluggishness: you can’t focus as well; your memory might be slightly off; and you are probably more irritable.
In this study, people participated in a two part trial. In the first part they slept in the lab and in the second they had to stay awake all night (they walked, browsed internet, watched movies etc.). The following morning the participants were shown a series of pictures of a person whose expression gradually progressed from non-threatening (slightly smiling) to threatening (angry looking). The participants were shown these pictures while having their brains scanned in an fMRI machine. fMRI measures blood flow in the brain and the idea is that blood flow represents energy required for the brain to complete an action. So more blood flow would mean that part of the brain was working hard to perform the task. The researchers focused on parts of the brain that are known to be involved in social threat discrimination, such as the cortex and the amygdala.
The participant’s brain interpreted how threatening they thought the facial expressions. The scans for each participant for sleep and no sleep trials were then compared. When the participants didn’t sleep their brains were less able to discriminate non-threatening from threatening facial expressions i.e. more of the facial expressions became threatening. And not only that… it also increased their body’s overall perception of threat with increased heart rate.
Isn’t that surprising? Just skipping one night of sleep severely impacts how your brain interprets threat. Not sleeping one night makes your brain see more enemies.
Dreaming helps with reality
When we are sleeping our brains are actually very active, performing major night-shift tasks such as memory consolidation and clean-up of excess neurochemicals. During this time, networks of brain cells work together and produce patterns of activity called oscillations. It is a little bit like a group of clocks ticking. Each clock ticks at its own rate but together they produce a pattern of ticking. Deep sleep or slow-wave sleep is characterized by low frequency oscillations such as delta or alpha, whereas dream sleep (you may have heard of REM, rapid eye movement, sleep) is characterized by high frequency oscillations called gamma. These oscillations can be monitored during sleep with electrodes on the scalp.
In this study, on the night that the participants slept their sleep oscillations were monitored. This is where sleep and reading faces gets even more interesting. What they found was that even on nights that the participants slept, the degree to which they could discriminate threatening versus non-threatening facial expressions was dependent on the amount of dream sleep (measured by the amount of gamma oscillations)! The more dreaming the participants did, the better they could read facial expressions.
Dreaming helped with reality!
Many people with neurological disorders such as schizophrenia and autism spectrum disorders have trouble reading faces. What is interesting is that people who suffer from these disorders also have alterations in gamma oscillations. You can learn more about gamma oscillations by viewing the Neurexpert video below:
This study suggests that lack of sleep (and perhaps not enough high quality sleep as measured by dreaming) makes friends into frenemies. That rude coffee guy. The person on the train next to you. The person walking behind you. Sleep deprivation is a symptom of our busy lives but also a symptom of many neurological disorders, such as schizophrenia, bipolar mood disorder and depression. Many of these disorders are also very isolating as not being able to read and navigate your social environment makes day-to-day interactions difficult. Reading faces is essential to social life.
The ironic thing about this result is that occupations that demand that people work long shifts or back-to back shifts with limited sleep are often those that require the ability to read threat in order to protect society. These occupations include law enforcement and military (and let’s not forget the ultimate caretakers with the greatest sleep deficit: new parents). If neutral faces are perceived as threatening it may change the way that a situation is handled. Suddenly more people are the enemy. The United States Navy just highlighted the importance of sleep in a study and is proposing a change in shift scheduling (click here for more details), but the same would go for soldiers on the front line, drone operators or police on the beat.
In conclusion, if you don’t want to get up in the morning feeling like the world is against you, then make sure you get enough sleep with plenty of dreaming.
To view the original paper discussed in this blog “Sleep Deprivation Impairs the Human Central and Peripheral Nervous System Discrimination of Social Threat” in Journal of Neuroscience please click here.
The Blog was written by Carolyn Lacey, Scientific Outreach Manager at Neurexpert. To learn more about Carolyn and Neurexpert, please click here.