Upset by something unpleasant?
We have all been there.
And we usually find we feel better about the next day.
At least: if you have restful REM sleep.
Stressful and upsetting events trigger a “siren” in out brains, to makes us more aware of potential danger.
Researchers at the Netherlands Institute for Neuroscience discovered why you will be better able to bear tomorrow what you are distressed about today. And why that can go wrong.
A good night’s sleep, specifically REM sleep, is needed to “reset” this siren in our brains.
The researchers placed their participants in a MRI scanner in the evening and presented a specific odour while they made them feel upset.
The brain scans showed how the amygdala became active.
The participants then spent the night in the sleep lab, while the activity of their sleeping brain was measured with EEG, and the specific odor was presented again on occasion.
The next morning, the researchers tried to upset their volunteers again, in exactly the same way as the night before. But now they did not succeed so well in doing this.
Brain circuits had adapted overnight; the siren of the brain no longer went off. The amygdala responded much less, especially in those who had had a lot of restful REM sleep and where meanwhile exposed to the specific odor.
The finding can be of great importance for about two-thirds of all people with a mental disorder, as both restless REM sleep and a hyperactive amygdala are the hallmarks of post-traumatic stress disorder (PTSD), anxiety disorders, depression and insomnia.
- People with PTSD carry their traumatic experience to the next day:
- People with an anxiety disorder take their greatest fear with them into the next day
- People with depression carry their despair into the next day
- People with chronic insomnia hold onto their tension into the next day
However, among the participants were also people with restless REM sleep.
Things went surprisingly different for them.
Brain circuits had not adapted well overnight: the siren of the brain continued to sound the next morning.
And while the nocturnal exposure to the odour helped people with restful REM sleep adapt, the people who had restless REM sleep felt worse by being exposed to the odour.
The evidence is that REM sleep helps “reset” some of the active pathways in the brain.
And it is this “resetting” that helps the upsets and anxieties of yesterday, fade away.