"This finding is worrying, especially in developed countries where two-thirds of the population suffers from sleep deprivation."
Andrea Goldstein Pikarski, a postdoctoral researcher at Stanford University who began the study while pursuing her doctorate and is also the study's first author, said, "This result is certainly ominous for the countless people suffering from sleep deprivation."
"Think about the students who study all night, the medical staff in the emergency room, the soldiers on the battlefield, and the police officers on night shifts. What does this mean?"
Researchers conducted an experiment on 18 healthy young adults, having them observe 70 different facial expressions, including smiles and threats, both after a full night's sleep and after 24 hours of sleep deprivation. The researchers scanned the participants' brains and measured their heart rates while they viewed these faces.
Andrea Goldstein Pikarski, a postdoctoral researcher at Stanford University who began the study while pursuing her doctorate and is also the study's first author, said, "This result is certainly ominous for the countless people suffering from sleep deprivation."
"Think about the students who study all night, the medical staff in the emergency room, the soldiers on the battlefield, and the police officers on night shifts. What does this mean?"
Researchers conducted an experiment on 18 healthy young adults, having them observe 70 different facial expressions, including smiles and threats, both after a full night's sleep and after 24 hours of sleep deprivation. The researchers scanned the participants' brains and measured their heart rates while they viewed these faces.
In this experiment, functional magnetic resonance imaging (fMRI) scans of the brain showed that sleep-deprived brains were unable to distinguish between friendly and threatening facial expressions, particularly in the anterior insula and anterior cingulate cortex expression-sensing areas.
Furthermore, when faced with threatening or friendly expressions, sleep-deprived participants not only exhibited abnormal heart rate responses, but also experienced disruptions in the neural connections between their brains and hearts that sense danger signals.
“Sleep deprivation seems to take the body out of the brain’s control,” Walker said. “That is to say, you can’t follow your heart.”
Therefore, when participants in the study were sleep-deprived, they even misinterpreted friendly, normal, or threatening facial expressions as other expressions.
“They made our Rorschach-style experiment fail,” Walker said. “Insufficient sleepers transfer rosy thoughts into their emotional world, greatly overestimating the threat. This could also explain why some people who are extremely sleep-deprived are not good at socializing or feel lonely.”
Another encouraging finding is that researchers, after recording participants' brain activity throughout the night, discovered that the quality of REM (Rapid Eye Movement) sleep, or dream sleep, is related to the accuracy of facial expression recognition. Walker's earlier research found that REM sleep reduces stress-producing neurochemicals and alleviates painful memories.
“The better the quality of dream sleep, the more accurately the brain and body can recognize facial expressions,” Walker explained. “Dream sleep seems to readjust the magnetic north of our emotional compass, so this study provides more evidence to prove the importance of sleep for humans.”
