Matthew Walker, a Professor of Psychology and Neuroscience at UC Berkeley, suggests that deciphering emotional expressions determine how two people interact with one another. According to the findings of his study, published in the Journal of Neuroscience, sleep-deprived brains cannot perform this function accurately, and might confuse friends with foes.

Discovering The Intriguing Association

The study involved 18 healthy young adults who were shown 70 different facial expressions. Experiments were conducted once after a full night’s sleep, and once after the participants stayed awake for 24 hours. Brain activity and heart rates were monitored during all experiments.

Brain scans – taken via Functional Magnetic Resonance Imaging (FMRI) – showed that sleep-deprived brains were unable to distinguish between expressions of menace and affection. Differences were observed particularly in the emotion-sensing regions, including the anterior insula and anterior cingulate cortex.

Similarly, heart rates of sleep-deprived participants did not exhibit normal responses towards threatening or friendly faces. Moreover, the neural between the heart and brain, which normally enables the body to assess signals of distress, was observed to be disconnected. “Sleep deprivation appears to dislocate the body from the brain”, suggested Walker. “You can’t follow your heart”.

Implications Of The Study

On the whole, results showed that sleep-deprived participants interpreted majority of the faces as threatening, including those which were neutral or friendly. Walker stated that these participants even failed the emotional Rorschach test. He added that lack of sleep causes an overestimation of threat, which could explain why people who get insufficient sleep tend to be less communal and more lonesome.

“These findings are especially worrying considering that two-third of people in the developed nations fail to get sufficient sleep”, highlighted Walker.

“Consider the implications for students pulling all-nighters, emergency-room medical staff, military fighters in war zones and police officers on graveyard shifts”, stated lead author Andrea Goldstein-Piekarski, a Postdoctoral Fellow at Stanford University who started the study as a Ph.D. student at UC Berkeley.

The Connection With REM

On the positive side, researchers recorded the electrical brain activity of participants during a full night’s rest and observed a correlation between the quality of Rapid Eye Movement (REM) – ‘dream sleep’ – and the ability to correctly decipher facial expressions. Previous studies by Walker have shown that REM sleep reduces stress neurochemicals and soothes painful memories. This implies that with good quality sleep, the brain and body becomes better at recognizing different facial expressions. Walker claims that this study provides more proof of the importance of sleep in our lives.