Scientists from the the University of Bern found how the brain triages emotions during dream sleep to consolidate the storage of positive emotions while dampening the consolidation of negative ones.
The work expands the importance of sleep in mental health and offers the way to new treatment strategies.
The research is published in Science and was conducted by Antoine Adamantidis et al.
Rapid eye movement (REM or paradoxical) sleep is a unique and mysterious sleep state during which most dreams occur together with intense emotional contents.
The prefrontal cortex integrates many of these emotions during wakefulness but appears paradoxically quiescent during REM sleep.
In humans, excessively negative emotions, such as fear reactions and states of anxiety, lead to pathological states like Post-Traumatic Stress Disorder (PTSD).
In the study, the team first conditioned mice to recognize auditory stimuli associated with safety and others associated with danger (aversive stimuli).
The activity of neurons in the brain of mice was then recorded during sleep-wake cycles.
Neurons are composed of a cell body (soma) that integrates information coming from the dendrites (inputs) and sends signals to other neurons via their axons (outputs).
The results obtained showed that cell somas are kept silent while their dendrites are activated during REM sleep.
This decoupling is important because the strong activity of the dendrites allows the encoding of both danger and safety emotions, while the inhibitions of the soma completely block the output of the circuit during REM sleep.
In other words, the brain favors the discrimination of safety versus danger in the dendrites, but blocks the over-reaction to emotion, in particular danger.
According to the researchers, this is beneficial to the stability and survival of organisms. This bi-directional mechanism is essential to optimize the discrimination between dangerous and safe signals.
If this discrimination is missing in humans and excessive fear reactions are generated, this can lead to anxiety disorders.
The findings are particularly relevant to pathological conditions such as post-traumatic stress disorders, in which trauma is over-consolidated in the prefrontal cortex, day after day during sleep.
These findings pave the way to a better understanding of the processing of emotions during sleep in humans and open new way to treat traumatic memories, such as post-traumatic stress disorders (PTSD) and their early sleep-dependent consolidation.
If you care about sleep, please read studies about the science on 3 traditional bedtime remedies, and this sleep supplement may help prevent memory loss, cognitive decline.
For more information about mental health, please see recent studies that eating too much sugar may make you have these mental problems, and results showing effective anxiety therapy can strongly change personality.
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