"That's a strong signal that tells you it wasn't just the passage of time that healed the wounds," Walker said. "It was sleep that caused the reduction in emotional reactivity."
And electroencephalographs of the participants who spent the night in the sleep lab pinpointed the times during the night when the chemicals were suppressed. It happened during the REM phase.
The dream phases of sleep allowed the participants to "cope" with their emotions, so when they saw the images the second time they could remember them from the first session, but without experiencing the emotional trauma again, he added.
Unfortunately, for PTSD victims, the pain remains, apparently because the REM phase is not doing what it ought to do. So a soldier who hears a car backfire may relive the terror of a combat experience because the emotional wounds are still open.
For the rest of us, a good night's sleep will at least soften the emotion.
"Mother nature has programmed us with some elegant biology that naturally does its thing every time we allow our heads to hit the pillow for a sufficient amount of sleep," Walker said.
"But we are in a society now that is desperately shortchanging our brains emotional regulation potential because we don't allow ourselves sufficient sleep.
"The average now seems to be below seven hours for the U.S. That's frightening."