“People need dreams, there’s as much nourishment in ’em as food,” said novelist Dorothy Gilman—and now researchers have found there is truth in her sentiment.
UC Berkeley researchers have found that during the dream phase of sleep, also known as REM sleep, our stress chemistry shuts down and the brain processes emotional experiences and takes the painful edge off difficult memories.
The findings offer an explanation for why people with post-traumatic stress disorder (PTSD), such as veterans, have a hard time recovering from painful experiences and suffer reoccurring nightmares, and they also offer clues into why we dream, according to a university press release.
“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,” said Matthew Walker, associate professor of psychology and neuroscience at UC Berkeley and senior author of the study.
“During REM sleep, memories are being reactivated, put in perspective and connected and integrated, but in a state where stress neurochemicals are beneficially suppressed,” said Els van der Helm, a doctoral student in psychology at UC Berkeley and lead author of the study.
“We know that during REM sleep there is a sharp decrease in levels of norepinephrine, a brain chemical associated with stress,” Walker said. “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.”
But for people with PTSD, Walker said, this overnight therapy may not be working effectively, so when a “flashback is triggered by, say, a car backfiring, they relive the whole visceral experience once again because the emotion has not been properly stripped away from the memory during sleep.”
The results offer some of the first insights into the emotional function of Rapid Eye Movement (REM) sleep, which typically takes up 20 percent of a healthy human’s sleeping hours, according to the press release. Previous brain studies indicate that sleep patterns are disrupted in people with mood disorders such as PTSD and depression.
The study was published in the journal Current Biology.