November 27, 2011
Science Daily/University of California - Berkeley
They say time heals all wounds, and new research indicates that time spent in dream sleep can help. 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.

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 edge off difficult memories.

The findings offer a compelling explanation for why people with post-traumatic stress disorder (PTSD), such as war veterans, have a hard time recovering from distressing experiences and suffer reoccurring nightmares. They also offer clues into why we dream.

"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 to be published on Nov. 23, in the journal Current Biology.

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. Previous brain studies indicate that sleep patterns are disrupted in people with mood disorders such as PTSD and depression.

"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."

Walker said he was tipped off to the possible beneficial effects of REM sleep on PTSD patients when a physician at a U.S. Department of Veterans Affairs hospital in the Seattle area told him of a blood pressure drug that was inadvertently preventing reoccurring nightmares in PTSD patients.
http://www.sciencedaily.com/releases/2011/11/111123133346.htm