Sleep-Deprived Brains Can’t Distinguish Between Friends and Foes

Amy Taylor July 16, 2015

Researchers from UC Berkeley found that sleep deprivation reduces our ability to accurately read facial expressions, which can lead to serious consequences, such as not noticing that a child is sick or in pain, or that a potential mugger or violent predator is approaching.

Recognising someone else’s facial expression is essential to truly understand what the person thinks and feels more than what he or she says. Like when speaking with a stranger, their facial expressions give us cue on deciding whether or not to interact with them.

The new findings, published in the Journal of Neuroscience, involved 18 healthy young adults who viewed 70 facial expressions that ranged from friendly to threatening, once after a full night of sleep, and once after 24 hours of being awake.

Researchers scanned the participants’ brains and measured their heart rates as they looked at the series of visages.

The fMRI results show that sleep-deprived brains could not distinguish between threatening and friendly faces, specifically in the emotion-sensing regions of the brain’s anterior insula and anterior cingulate cortex.

According to Matthew Walker, a professor of psychology and neuroscience at UC Berkeley, and the senior author of the study, the findings were especially worrying since two-thirds of people in the developed nations fail to get sufficient sleep.

"Recognising 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," he said.

Moreover, the heart rates of sleep-deprived participants did not respond normally to threatening or friendly facial expressions. Researchers also found a disconnection in the neural link between the brain and heart that typically enables the body to sense distress signals.

As a consequence, they interpreted more faces, even the friendly or neutral ones, as threatening when sleep-deprived

Meanwhile, participants who had enough sleep had more of Rapid Eye Movement (REM) or dream sleep which correlated with their ability to accurately read facial expressions.

"Sleep deprivation appears to dislocate the body from the brain," said Walker. "You can’t follow your heart."

"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."

Source of this article: Sleep Deprivation Impairs the Human Central and Peripheral Nervous System Discrimination of Social Threat