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The brain uses a triaging system to process emotions when we are dreaming, storing the positive ones while dampening negative emotions, a new study has found.
Researchers at the University of Bern, Switzerland, and University Hospital Bern say the study, which was published in the journal Science, provides new information about the connection between sleep and mental health, and also could suggest new therapies for treating traumatic memories.
During rapid eye movement (REM) sleep, dreams happen alongside intense emotions but scientists have struggled to understand how these emotions are reactivated. Although the prefrontal cortex of the brain is responsible for integrating many of these emotions when people are awake, it doesn't appear to play an active role in REM sleep.
"The mechanism of REM sleep, in particular, is very important for emotional health," the research group leader, Professor Antoine Adamantidis of the Department of Biomedical Research (DBMR) at the University of Bern, told Newsweek.
Mapping dream sleep
In experiments with mice, the researchers examined the behavior of neurons in the brain; neurons are composed of a cell body (soma), which processes information coming from the dendrites (inputs) and sends signals to other neurons.
The research results show that cell somas are kept silent, or asleep, when their dendrites are activated and awake, according to Adamantidis, indicating a decoupling of the two cellular compartments. Through this process, the strong "wakeful" activity of the dendrites allows for both danger and safety emotions to be encoded. At the same time, the inhibition of the soma enables the brain to favor the discrimination of safety versus danger in the dendrites but blocks overreaction to emotion, and danger in particular.
By understanding this process, the researchers open up the possibility of a mechanistic approach to treating mental health disorders, Adamantidis added.
Signposts for anxiety conditions
Particularly strong negative emotions, such as fear and anxiety, can contribute to conditions such as post-traumatic stress disorders (PTSD). In PTSD, trauma is overconsolidated in the prefrontal cortex daily during sleep.
By offering a clearer understanding of how emotions are processed during sleep in humans, the Bern research could provide new insights into potential targets for treating the faulty processing of traumatic memories such as PTSD.
"It seems that sleep is considered a window of opportunity for treatment of mental disorders," Adamantidis says, adding that his team's research demonstrated the possibility of modulating brain activity to treat other disorders, including depression.
