The study was conducted by researchers at Northwestern University Feinberg School of Medicine in Chicago who recruited around 15 healthy young adults. They were shown two faces and were exposed to a different odor for each face and were also given mild electric shocks. After associating the face and odor to the fear of getting a shock, the participants were exposed to an odor when they were sleeping, but without being shown the face or given electric shocks.
On showing both the faces when they woke up, the researchers found that their fear reactions to the face that was linked with the odor that they had been exposed to when sleeping was slower compared to the other face.
"Sleep sort of stamps memories in more strongly. That's when a lot of memory formation can take place. From a clinical perspective, this can be a new approach to try and treat stressful or traumatic memories", lead researcher Jay Gottfried said.