During the dream phase of sleep – also known as REM sleep – our stress chemistry shuts down and allows the brain to process emotional experiences, a new study has found. This takes the edge off difficult memories.“We know that during REM sleep there is a sharp decrease in levels of norepinephrine, a brain chemical associated with stress,” says Matthew Walker associate professor of psychology and neuroscience at UC Berkeley.
“By reprocessing previous emotional experiences in this neuro-chemically safe environment of low norepinephrine during REM sleep, we wake up the next day, and those experiences have been softened in their emotional strength.
“We feel better about them, we feel we can cope.”
Els Van der Helm, lead author of the study explains that during REM sleep memories are reactivated but “put in perspective and connected and integrated”.
This happens while the brain’s stress neurochemicals are “beneficially suppressed”.
Thirty–five healthy young adults participated
in the study. They were divided into two groups, but all shown 150 emotional images twice and 12 hours apart.
An MRI scanner measured their brain activity.
Half of them saw the images in the morning and again in the evening.
The other half saw them in the evening, had a night’s sleep and viewed them again the following morning.
Those who slept in between image viewings reported a significant decrease in their emotional reaction to the images.
In addition, MRI scans showed a dramatic reduction in reactivity in the part of the brain that processes emotions, allowing the brain’s “rational” part to regain control of the participants’ emotional reactions.
The study also concluded that in people with Post Traumatic Stress Disorder – who have a hard time recovering from painful memories – the dream stage may not be working effectively.
The study is published in the journal Current Biology.