First evidence that fear memories can be reduced during sleep

September 22, 2013
The right hippocampus (shown in the blue box) was one of the brain regions that showed significant changes in activity after fear memory reactivation during sleep. Credit: Dr. Katherina K. Hauner

A fear memory was reduced in people by exposing them to the memory over and over again while they slept. It's the first time that emotional memory has been manipulated in humans during sleep, report Northwestern Medicine scientists.

The finding potentially offers a new way to enhance the typical daytime treatment of phobias through exposure therapy by adding a nighttime component. Exposure therapy is a common treatment for phobia and involves a gradual exposure to the feared object or situation until the fear is extinguished.

"It's a novel finding," said Katherina Hauner, a 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."

Hauner did the research in the lab of Jay Gottfried, associate professor of neurology at Feinberg and senior author of the paper.

The study will be published Sept. 22 in the journal Nature Neuroscience.

Previous projects have shown that spatial learning and motor sequence learning can be enhanced during sleep. It wasn't previously known that emotions could be manipulated during sleep, Northwestern investigators said.

In the study, 15 healthy human subjects received mild electric shocks while seeing two different faces. They also smelled a specific odorant while viewing each face and being shocked, so the face and the odorant both were associated with fear. Subjects received different odorants to smell with each face such as woody, clove, new sneaker, lemon or mint.

Then, when a subject was asleep, one of the two odorants was re-presented, but in the absence of the associated faces and shocks. This occurred during when is thought to occur. Sleep is very important for strengthening , noted Hauner, 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 ," 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 fMRI (functional magnetic resonance imaging). 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 reactivity that was specific to the targeted face image associated with the presented during sleep.

Explore further: People with spider phobia handle tarantulas, have lasting changes in brain after short therapy

Related Stories

Diminishing fear vicariously by watching others

September 16, 2013

Phobias—whether it's fear of spiders, clowns, or small spaces—are common and can be difficult to treat. New research suggests that watching someone else safely interact with the supposedly harmful object can help to extinguish ...

Recommended for you

New insights on how cocaine changes the brain

November 25, 2015

The burst of energy and hyperactivity that comes with a cocaine high is a rather accurate reflection of what's going on in the brain of its users, finds a study published November 25 in Cell Reports. Through experiments conducted ...

Can physical exercise enhance long-term memory?

November 25, 2015

Exercise can enhance the development of new brain cells in the adult brain, a process called adult neurogenesis. These newborn brain cells play an important role in learning and memory. A new study has determined that mice ...

Umbilical cells help eye's neurons connect

November 24, 2015

Cells isolated from human umbilical cord tissue have been shown to produce molecules that help retinal neurons from the eyes of rats grow, connect and survive, according to Duke University researchers working with Janssen ...

Brain connections predict how well you can pay attention

November 24, 2015

During a 1959 television appearance, Jack Kerouac was asked how long it took him to write his novel On The Road. His response – three weeks – amazed the interviewer and ignited an enduring myth that the book was composed ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.