London: If you feel cranky or grumpy after a night without sleep, it is because your brain's ability to regulate emotions gets compromised by fatigue, say researchers.
This is a bad news for adults who get less than six hours of sleep in night.
The team from Tel Aviv University identified the neurological mechanism responsible for disturbed emotion regulation and increased anxiety due to only one night's lack of sleep.
The research reveals the changes sleep deprivation can impose on our ability to regulate emotions and allocate brain resources for cognitive processing.
"Prior to our study, it was not clear what was responsible for the emotional impairments triggered by sleep loss," said professor Talma Hendler of TAU's Sackler Faculty of Medicine.
The team assumed that sleep loss would intensify the processing of emotional images and thus impede brain capacity for executive functions.
"We were actually surprised to find that it significantly impacts the processing of both neutral and emotionally-charged images," Hendler added. "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," she said.
For the results, the researchers kept 18 adults awake all night to take two rounds of tests while undergoing brain mapping.
When sleep-deprived, participants performed badly in the cases of both the neutral and the emotional images and their electrical brain responses did not reflect a highly different response to the emotional images.
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"It could be that sleep deprivation universally impairs judgment, but it is more likely that a lack of sleep causes neutral images to provoke an emotional response," the team noted.
The team also found that participants after only one night of lack of sleep were distracted by every single image (neutral and emotional).
"We revealed a change in the emotional specificity of Amygdala, a region of the brain associated with detection and valuation of salient cues in our environment, in the course of a cognitive task," Hendler said.
These results reveal that without sleep, the mere recognition of what is an emotional and what is a neutral event is disrupted.
The results appeared in the Journal of Neuroscience.