Processing emotions, especially distinguishing between danger and safety emotions, is critical to the survival of animals. In humans, excessive negative emotions, such as fear and anxiety, can lead to pathological emotions such as post-traumatic stress disorder (PTSD).

In Europe, around 15% of the population is significantly affected by persistent anxiety and severe mental illness.

Recently, by Antoine Adamantidis of the Department of Neurology of the University of Switzerland and the University Hospital of Bern The research team led by the professor provides important insights into how the brain helps to strengthen positive emotions and weaken strong negative or traumatic emotions during dream sleep.

In this study, scientists found that the brain categorizes emotions during dream sleep and consolidates the store of positive emotions while suppressing negative ones. The researchers say the work highlights the importance of sleep in mental health and opens up new treatment strategies.

The prefrontal cortex integrates many of these emotions during wakefulness, but suddenly becomes quiescent during REM sleep. "Our goal was to understand the underlying mechanism and function of this surprising phenomenon." Department of Neurology, University Hospital Bern Professor Antoine Adamantidis said.

01 Breakthrough in sleep medicine

Rapid eye movement sleep (REM) is a unique and mysteriously important sleep state in which most dreams occur with intense emotional content. How and why these emotions are reactivated is unclear.

To explore this sleep question, the researchers first asked mice to identify safety-related auditory stimuli, as well as other danger-related auditory stimuli (aversive stimuli), and then recorded neurons in the mouse brains during the sleep-wake cycle. important activities.

In this way, the researchers were able to map different regions of the cell and determine how memory is transformed during REM sleep.

The soma of a neuron that integrates information from the dendrites (inputs) and sends important signals to other neurons through its axons (outputs). But the findings showed that when their dendrites were activated, the cell bodies remained silent.

"This means decoupling of the two cellular compartments, in other words, the cell body is fully asleep and the dendrites are fully awake," explains Adamantidis. This decoupling is important because intense activity in dendrites allows for the encoding of danger and safety emotions, whereas inhibition of the soma completely blocks the output of the signal during REM sleep.

In other words, the brain tends to distinguish safety from danger in its dendrites, but blocks overreaction to emotions, especially danger.

The researchers believe that the coexistence of these two mechanisms is beneficial for the stability and survival of the organism. If humans lack this distinction and develop an excessive fear response, this can lead to anxiety disorders. These findings are particularly relevant to pathological conditions such as post-traumatic stress disorder, in which traumatic memories are over-consolidated in the prefrontal cortex day after day during sleep.

Furthermore, these findings pave the way for a better understanding of emotional processing during human sleep and open important perspectives for the treatment of traumatic memories, such as post-traumatic stress disorder (PTSD). Other acute or chronic mental health problems that may be associated with this somatic dendritic decoupling during sleep include acute and chronic stress, anxiety, depression, panic, and even anhedonia, the inability to feel pleasure.

Sleep research and sleep medicine have long been a research focus at the University of Bern and the University Hospital of Bern. "We hope our findings will be of interest not only to patients, but to the general public," Adamantidis said.

02 The importance of sleep

Nowadays, sleep difficulty has become an important problem affecting the health of modern people. More than 300 million people in my country have sleep disorders, and the incidence of different degrees of sleep difficulties in adults is close to 40%. The quality of sleep not only affects one's mood, but also affects one's immune system. Moreover, difficulty sleeping is often one of the external manifestations of an underlying disease in the body.

Why is sleep so important? According to Yu Hayashi from the International Institute of Integrative Sleep Medicine, University of Tsukuba, Japan Research by the professor's research team has found that blood flow to the brain increases significantly during mammalian REM sleep, which is critical for the removal of accumulated waste from the brain.

We all know that sleep is vital to our health, and after a few nights without a good night’s sleep, we will feel restless, inefficient in study, lack of appetite, and more. After all, people spend one-third of their life sleeping, and lack of sleep can lead to a series of problems such as obesity, cardiovascular and cerebrovascular diseases, and depression.