Fears Can Be Erased While We Sleep

Our specific fears, whether of clowns, spiders or heights, may seem the stuff of nightmares, but sleep, in fact, holds promise for purging our minds of those phobias, new research shows. During sleep, researchers told the Washington Post, memories become engrained in our minds. But during this vulnerable time they can also be manipulated and undone.

In the new study, neuroscientists experimented on a small group of 15 participants. They conditioned their subjects to fear two faces in a line up of several photos by giving them a mild electric shock each time those faces flashed by. They also created an odor association with each of those faces, such as lemon, rose, mint or wood. All the while, they monitored their subjects’ fear responses by measuring sweat and electrical conductance of the participants’ skin, confirming that their participants did indeed develop a fear response to those electrically charged faces.

The researchers specifically sought people who excelled in the art of napping, The Scientist says, and after receiving their shock conditioning, the subjects each took a two hour nap without being told anything about what would happen to them while they slept. The researchers exposed the sleeping participants to the same smells from the earlier study and took measurements of their fear responses. At first, the smells associated with the faces of pain elicited a spike in fear, but as the nap continued, the fear response those smells induced waned.

Once awake, the participants were less afraid of the faces they had been conditioned to fear whose corresponding odors they had been exposed to while asleep than those whose corresponding odors they had not smelled during their naps.

fMRI images of the participants’ brain activity before and after the nap also confirmed that the way they processed those fearful faces had essentially changed, The Scientist adds. To be certain that the nap was the key factor in extinguishing the subjects’ fear, the researchers repeated the experiment in another group, this time asking participants yo watch a nature documentary instead of taking a snooze. Those people’s fears did not subside, indicating that something about sleeping allows our minds to be more malleable when it comes to imprinting and erasing fear.

More from Smithsonian.com:

What Scientists Now Know About Repairing Memory
We Can Only Process Thirty Smells at a Time

Rachel Nuwer | | READ MORE

Rachel Nuwer is a freelance science writer based in Brooklyn.