For many patients with phobias, typical treatment involves gradual exposure to the feared object or situation. But researchers have now found that emotional memory can be manipulated during sleep, paving the way to new phobia treatments as we dream.
The researchers, from Northwestern University, published the results of their study in the journal Nature Neuroscience.
They note that previous projects have demonstrated spatial learning and motor sequence learning can be strengthened during sleep, but until now, emotional memory has never been manipulated during slumber.
In the study, the researchers gave 15 healthy volunteers mild electric shocks while two different faces were presented to them. The volunteers also smelled different odorants – such as clove, new sneaker or mint – while looking at each face and being shocked.
This linked the face and the smells with fear for the volunteers, say the researchers.
As the subjects were sleeping, one of the odorants was released, but this time the faces and shocks were absent. The researchers released the odorant during slow wave sleep, which is when they say “memory consolidation” occurs.
Katherine Hauner, from the Northwestern University Feinberg School of Medicine, says:
“While this particular odorant was being presented during sleep, it was reactivating the memory of that face over and over again, which is similar to the process of fear extinction during exposure therapy.”
After the subjects awoke, they were then shown both faces. However, when presented with the face linked to the odor they smelled during sleep, their fear levels were lower than when the saw the other face.
The research team notes that fear was measured in two ways:
- Through amounts of sweat in the skin (similar to a lie detector test)
- Through functional magnetic resonance imaging (fMRI).
The results from the fMRI revealed that there were changes in regions linked with memory, such as the hippocampus, as well as changes in emotion regions, such as the amygdala.
These changes, say the team, show a “decrease in reactivity” linked to the face associated with the odor the volunteers smelled during sleep.
Hauner says:
“It’s a novel finding. 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.”
The benefit of fighting fears during sleep, notes the team, is that fear extinction can be carried out without having to endure re-exposure to the feared object or situation.
Medical News Today recently reported that researchers found sleep helps boost reproduction of the cells involved in brain repair.