Jerusalem: Feeling cranky or grumpy after a night without sleep? It is because your brain's ability to regulate emotions is probably compromised by fatigue, a new study has found. Researchers at the Tel Aviv University (TAU) in Israel have identified the neurological mechanism responsible for disturbed emotion regulation and increased anxiety due to only one night's lack of sleep.
The research shows the changes sleep deprivation can impose on our ability to regulate emotions and allocate brain resources for cognitive processing. For the study, researchers kept 18 adults awake all night to take two rounds of tests while undergoing brain mapping, first following a good night's sleep and the second following a night of lack of sleep in the lab.
One of the tests required participants to describe in which direction small yellow dots moved over distracting images. These images were 'positively emotional' (a cat), 'negatively emotional' (a mutilated body), or 'neutral' (a spoon). When participants had a good night's rest, they identified the direction of the dots hovering over the neutral images faster and more accurately, and their electroencephalogram (EEG) pointed to differing neurological responses to neutral and emotional distractors.
Sleep-deprived participants performed badly in the cases of both the neutral and the emotional images, and their electrical brain responses, as measured by EEG, did not reflect a highly different response to the emotional images. This pointed to decreased regulatory processing, researchers said. They conducted a second experiment testing concentration levels. Participants were shown neutral and emotional images while performing a task demanding their attention while ignoring distracting background pictures with emotional or neutral content - the depression of a key or button at certain moments - while inside an Functional magnetic resonance imaging (fMRI) scanner.
The team found that participants after only one night of lack of sleep 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 major limbic node responsible for emotional processing in the brain.
"We revealed a change in the emotional specificity of the amygdala, a region of the brain associated with detection and valuation of salient cues in our environment, in the course of a cognitive task," said Talma Hendler, a professor at TAU. "These results reveal that, without sleep, the mere recognition of what is an emotional and what is a neutral event is disrupted," said Hendler. The findings were published in the Journal of Neuroscience.
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