Researchers from the University of California, Berkeley, found that our brains process emotional experiences during dreams, which is the Rapid Eye Movement (REM) phase of sleep, and this takes the painful edge off difficult memories.“During REM sleep, memories are being reactivated, put in perspective and connected and integrated, but in a state where stress neurochemicals are beneficially suppressed,” study author Els van der Helm was quoted as saying by ‘Daily Mail’.

For their study, the researchers recruited 35 healthy young adults and divided them into two groups. Each of them was showed about 150 emotional images twice in 24 hours while an MRI scanner measured their brain activity.

Half of the participants viewed the images in the morning and again in the evening, staying awake between the two viewings, while the other half saw the images in the evening and again the next morning after a full night of sleep. Those who slept in between image viewings reported a significant decrease in their emotional reaction to the images.

MRI scans, they said, showed sleep caused a dramatic reduction in reactivity in the amygdala — a part of the brain that processes emotions. This allowed the brain’s “rational” prefrontal cortex to regain control of the participants’ emotional reactions, the researchers said.In addition, overnight recordings of the participant’s electrical brain activity showed levels of stress neurochemicals reduced during sleep.

Co-author Professor Matthew Walker, said: “The dream stage of sleep, based on its unique neurochemical composition, provides us with a form of overnight therapy, a soothing balm that removes the sharp edges from the prior day’s emotional experiences.”