Around two-thirds of people in developed nations do not get enough sleep. Insufficient sleep can lead to a number of issues including, finds a new study from University of California, Berkeley, a reduced ability to read facial expressions. The study suggests that sleep-deprived individuals overestimate the level of threat that other people present.
For the study, 18 healthy adults viewed 70 facial expressions after a full night’s sleep and again after being awake for 24 hours. While the participants viewed the expressions, the researchers scanned their brains using functional magnetic resonance imaging (fMRI) and monitored their heart rates. The researchers also recorded the participants’ electrical brain activity during their full night of sleep.
The participants exhibited significant differences in their response to facial expressions when they were sleep deprived compared to when they were well rested. Sleep-deprived participants’ brain scans revealed that the brain could not distinguish between threatening and friendly faces. This was especially apparent in the emotion-sensing regions of the anterior insula and the anterior cingulate cortex. When sleep deprived, participants’ heart rates did not respond normally to facial expressions and a neural link between the brain and heart that helps regulate stress became disconnected. Study participants found more faces to be threatening, including friendly faces, when they had not slept.
The study also found that Rapid Eye Movement (REM) sleep quality was correlated to the ability to accurately read facial expressions. REM sleep is known to reduce stress-related neurochemicals.
“The better the quality of dream sleep, the more accurate the brain and body was at differentiating between facial expressions. Dream sleep appears to reset the magnetic north of our emotional compass. This study provides yet more proof of our essential need for sleep,” concluded senior author Matthew Walker, professor of psychology and neuroscience at UC Berkeley
This research is published in the Journal of Neuroscience.
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