Researchers were able to reduce a fearful memory in a person without drugs.
How? By exposing them to the memory over and over again while they slept.
The researchers claim it’s the first time that emotional memory has been manipulated in humans during sleep.
The finding offers the potential of enhancing typical daytime treatment of phobias through exposure therapy by adding a nighttime component, the researchers noted.
Exposure therapy, a common treatment for phobia, involves a gradual exposure to the feared object or situation until the fear is extinguished, they explain.
“It’s a novel finding,” said Katherina Hauner, Ph.D., a postdoctoral fellow in neurology at Northwestern University Feinberg School of Medicine.
“We showed a small but significant decrease in fear. If it can be extended to pre-existing fear, the bigger picture is that, perhaps, the treatment of phobias can be enhanced during sleep.”
In the study, 15 healthy people received mild electric shocks while seeing two different faces. They also smelled a specific odor while viewing each face and being shocked, so the face and the odor were associated with fear, the researchers explain.
Then, when the person was asleep, one of the two odors was introduced into the room, in the absence of the associated faces and shocks. This occurred during slow wave sleep when memory consolidation is thought to occur, the researchers said.
Sleep is very important for strengthening new memories, added Hauner, a research scientist at the Rehabilitation Institute of Chicago.
“While this particular odor was being presented during sleep, it was reactivating the memory of that face over and over again. [This] is similar to the process of fear extinction during exposure therapy,” Hauner said.
When the subjects woke up, they were exposed to both faces. When they saw the face linked to the smell they had been exposed to during sleep, their fear reactions were lower than their fear reactions to the other face.
Fear was measured in two ways: Through small amounts of sweat in the skin, similar to a lie detector test, and through neuroimaging with functional magnetic resonance imaging (fMRI).
The fMRI results showed changes in regions associated with memory, such as the hippocampus, and changes in patterns of brain activity in regions associated with emotion, such as the amygdala.
These brain changes reflected a decrease in reaction that was specific to the face associated with the odor presented during sleep, the researchers found.
Source: Northwestern University