Cranky or grumpy after a long night? Fatigue puts most people in a bad mood, but a new Israeli study pinpoints the neurological mechanism responsible for increased anxiety due to only one night’s lack of sleep.
“Prior to our study, it was not clear what was responsible for the emotional impairments triggered by sleep loss,” Tel Aviv University’s Prof. Talma Hendler, who led the study, said in a statement. “It turns out we lose our neutrality. The ability of the brain to tell what’s important is compromised. It’s as if suddenly everything is important.”
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Hendler’s research team “assumed that sleep loss would intensify the processing of emotional images and thus impede brain capacity for executive functions;” however, “we were actually surprised to find that it significantly impacts the processing of both neutral and emotionally-charged images,” she says.
Sleep deprivation could lead to poor judgment and anxiety
To detect emotional responses, the researchers measured the electrical neurological activity in participants’ brains (using EEG and/or fMRI) and then showed the participants images designed to invoke different emotional responses. Images of cats were associated with positive emotions, while images of mutilated bodies were associated with negative emotions. Common objects, such as a spoon were deemed neutral images.
When participants had a good night’s rest, neurological tests indicated that participants had various responses, depending on whether the image was emotionally positive, negative or neutral. In contrast, responses of sleep-deprived participants were significantly less differentiated.
To test concentration levels, the researchers conducted a second experiment in which participants were asked to complete a simple task while distracting images (neutral and emotional) were displayed in the background. The team found that after one night without sleep, participants were distracted by every single image (neutral and emotional), while well-rested participants were only distracted by emotional images.
The effect was indicated by activity change in the amygdala, a set of neurons responsible for emotional processing in the brain.
According to Hendler, “these results reveal that, without sleep, the mere recognition of what is an emotional event and what is a neutral event is disrupted. We may experience similar emotional provocations from all incoming events, even neutral ones, and lose our ability to sort out more or less important information. This can lead to biased cognitive processing and poor judgment as well as anxiety.”
The study was recently published in the Journal of Neuroscience. The researchers are currently examining how novel methods for sleep intervention may help the treatment of anxiety, depression, and traumatic stress disorders in which emotional regulation may also be affected by sleep.