Scientists identify how the brain assesses emotions during dream sleep | Science-Environment

Scientists at the Department of Neurology from the University of Bern and the University Hospital Bern has determined how sleep aids in emotional processing. The research is published in the journal Science.

The work increases the importance of sleep in mental health and opens new avenues for therapeutic strategies. Rapid eye movement sleep (REM or paradoxical) is a unique and mysterious sleep state in which most dreams occur along with intense emotional content. How and why these emotions are reactivated is unclear. The prefrontal cortex integrates many of these emotions during wakefulness, but appears paradoxically quiet during REM sleep.

“Our aim was to understand the underlying mechanism and functions of such a surprising phenomenon,” said Prof. Antoine Adamantidis of the Department of Biomedical Research (DBMR) at the University of Bern and the Department of Neurology at the Inselspital, University Hospital of Bern. Processing emotions, especially distinguishing between danger and safety, is critical to the survival of animals. In humans, excessive negative emotions, such as fear responses and anxiety states, lead to pathological states such as post-traumatic stress disorder (PTSD). In Europe, about 15 percent of the population suffers from persistent anxiety and severe mental illness. The research group led by Antoine Adamantidis now provides insight into how the brain helps to amplify positive emotions and attenuate strongly negative or traumatic emotions during REM sleep.

The researchers first conditioned mice to recognize auditory stimuli related to safety and others related to danger (aversive stimuli). The activity of neurons in the mouse brain was then recorded during sleep-wake cycles. In this way, the researchers were able to map different parts of a cell and determine how emotional memories are transformed during REM sleep. Neurons are composed of a cell body (soma) that integrates information from the dendrites (inputs) and sends signals to other neurons through their axons (outputs). The results obtained showed that cell somas are kept still while their dendrites are activated. “This means a disconnection of the two cell compartments, in other words, soma wide asleep and dendrites wide awake,” explains Adamantidis. 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 distinction between safety and danger in the dendrites, but blocks the overreaction to emotion, especially danger.

A survival advantage According to the researchers, the co-existence of both mechanisms is beneficial for the stability and survival of the organisms: “This bidirectional mechanism is essential to optimize the distinction between dangerous and safe signals,” says Mattia Aime of the DBMR, first author of the study. If this distinction is missing in humans and excessive anxiety reactions are evoked, this can lead to anxiety disorders. The findings are particularly relevant for pathological conditions such as post-traumatic stress disorder, in which the trauma is overconsolidated day in, day out during sleep in the prefrontal cortex.

Breakthrough for sleep medicine These findings pave the way for a better understanding of emotional processing during sleep in humans and open new perspectives for therapeutic targets for treating maladaptive processing of traumatic memories, such as post-traumatic stress disorder (PTSD) and their early sleep – dependent consolidation. Additional acute or chronic psychological problems that may imply this somatodendritic disconnection during sleep include acute and chronic stress, anxiety, depression, panic or even anhedonia, the inability to feel pleasure. Sleep research and sleep medicine have long been a research focus of the University of Bern and the Inselspital, the University Hospital of Bern. “We hope that our findings will be of interest not only to the patients, but also to the general public,” says Adamantidis. (ANI)

(This story has not been edited by Devdiscourse staff and is generated automatically from a syndicated feed.)

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