REM sleep silences the siren of the brain

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REM sleep silences the siren of the brain

Restless REM sleep a risk for many mental disorders?

Upset by something unpleasant? We've all been there. Fortunately, sleep could help us; especially if it is restorative sleep. Researchers at the Netherlands Institute of Neurosciences have discovered why this quality of sleep helps us eliminate our bad experiences of the day.

Restorative sleep helps us to free ourselves from our experiences
Something scary or unpleasant does not go unnoticed. In our brain, the limbic circuit of cells and connections becomes immediately active. First and foremost, such experiments activate the amygdala. This nucleus of cells located deep in the brain can be considered the brain's alert system.

For the brain to work properly, this system must also be disabled. For this, a restful sleep, the part of sleep where dreams are the longest, is essential.

The researchers placed participants in an MRI scanner in the evening and gave them a specific smell while disturbing them. Brain tests showed how the tonsil became active. Participants then spent the night in the sleep laboratory, while the activity of their sleeping brains was measured with the EEG and the smell was occasionally presented again.

The next morning, the researchers tried again to upset the volunteers, just like the previous day. But they have not been as successful in doing so. Brain circuits had adapted overnight; the brain's warning system no longer worked. Their tonsils had reacted much less, especially in those who had slept in a deep restorative sleep.

However, among the participants who also included people with restless REM sleep. Things were surprisingly different for them. The brain circuits had not adapted well: the brain's warning system continued to function the next morning after they woke up. And while nighttime exposure to odour helped people in restorative sleep to adapt, the same exposure only made things worse for people who had experienced restless REM sleep.

The traces of our experiences are adjusted during sleep
During sleep, the "traces" of our experiences from the previous day are read spontaneously, like a film. Among all the vestiges of the day, a trace of our specific experiences can be activated by presenting the same pattern when you are awake. While the traces of our experiences are adjusted during sleep because some connections between brain cells are strengthened, others are weakened. Restless REM sleep disrupts these nocturnal adjustments that are essential for recovery and adaptation to a bad experience.

This finding could be of great importance to about two-thirds of all people with mental disorders, as restless REM sleep and an overactive tonsil characterize post-traumatic stress disorder (PTSD), anxiety disorders, depression and insomnia.

People with PTSD keep their traumatic experience inside for months: people with anxiety disorders keep their greatest fear inside them, depressed people keep their despair and chronic insomniacs keep their tension.

A treatment for people with these diseases
The authors of this study - Rick Wassing, Frans Schalkwijk and Eus van Someren - believe that treatment of restless REM sleep could help in a transdiagnostic way to treat emotional memories and help people with these diseases.