Ever since the dawn of humanity, people have wondered about the purpose of dreams. We’ve imbued these mental meanderings with all sorts of powers, from forecasting the future to providing a window into the soul.
But scientists say they now know what dreams are for: they sooth the sting out of troubling memories. And when dreams don’t do their job, horrific memories can take over a person’s life, as they do with PTSD, a new study suggests.
Matthew Walker and colleagues at the University of California, Berkeley, found that the brain uses dreams to strip the emotional content from memories of painful events.
Here’s how the researchers think it works. During dream, or REM, sleep, our brain chemistry changes, leaving us with lower levels of stress hormones. While we’re in this quieter state, the brain mulls over what happened and then files away the memory – but with less emotion attached.
So, when everything works right, when we later recall these events we’ll remember what happened, but less of the pain associated with them.