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Recurring fear memories can be reduced during sleep, suggests study

A new study by researchers at Northwestern University claim that being exposed to a recurring fear during sleep could help reduce phobias.

Systematic desensitization is often used in behavior therapy for the treatment of anxiety and phobias, where patients are gradually exposed to their object or situation of fear, until the fear itself fades away.

Better known as exposure therapy, it is a form of counter conditioning, a type of Pavlovian therapy, while patients are awake and able to see their fear, while the researchers in question used a similar method, but did it during sleep sessions and using smells.

The researchers showed 15 healthy people pictures of two different faces and at the same time were given a mild electric shock, as they were exposed to a different smell, such as lemon, mint, new trainers, clove or wood, new sneakers.

They were then taken into a sleep lab and while they were in a deep sleep, also known as slow-wave sleep - where new memories as well as emotions are consolidated, - they were again exposed to the same smell linked to one of the faces they had been shown.

On waking they were shown the two faces again, without the smell or electric shock. and the test subjects showed less fear of the image that had been linked to the odor they had smelt while asleep, than when shown the other face.

Responses were measured by the amount of sweat on the skin and MRI scans of the brain function that revealed changes in the hippocampus, a region associated with memory, and the amygdala, which is believed to affect emotion.

“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,” Katherina Hauner, a postdoctoral fellow in neurology at Northwestern University Feinberg School of Medicine and also a research scientist at the Rehabilitation Institute of Chicago.

“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,” she continued.

The study was published in the journal of Nature Neuroscience.

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