People unlearned an
odor's unpleasant accompaniment when they smelled it in their sleep
By Laura Sanders in Science News
A nap can ease the
burden of a painful memory. While fast asleep, people learned that a previously
scary situation was no longer threatening, scientists report September 22 in Nature
Neuroscience.
The results are the
latest to show that sleep is a special state in which many sorts of learning
can happen. And the particular sort of learning in the new study blunted a fear
memory, a goal of treatments for disorders such as phobias and post-traumatic stress
disorder.
“It’s a remarkable
finding,” says sleep neuroscientist Edward Pace-Schott of Harvard Medical
School and Massachusetts General Hospital.
Researchers led by
Katherina Hauner of Northwestern University’s Feinberg School of Medicine first
taught 15 (awake) volunteers to fear the combination of a face and odor.
Then the volunteers
tucked in for a nap in the laboratory. When the participants hit the deepest
stage of sleep, called slow-wave sleep, Hauner and her colleagues redelivered
the smell that had earlier come with a shock.
During the nap, some
participants had learned that the smell was safe. The volunteers sweated less
(a measure of fear) when the face-odor combination appeared after the nap, the
scientists found. When the odor wasn’t presented during sleep, volunteers’
responses to the associated face were unchanged.
Upon awakening,
volunteers also underwent scans that revealed changes in brain activity that
accompanied this relearning. Odor exposure while sleeping seemed to cause
neural changes in the hippocampus, a memory center, and the amygdala, which is
linked to emotions.
This relearning process
is similar to exposure therapy, Hauser says. In that type of therapy, a person
with arachnophobia, for instance, confronts spiders over and over again until
new memories of safety override the previous memory of fear.
Exposure therapy
is often very difficult for people, says neuroscientist Asya Rolls of
Technion--Israel Institute of Technology. A treatment that could happen
entirely during sleep, while the patient has no conscious knowledge of it,
might be easier on people, she says. “These are very promising findings,” she
says, “and I am excited to see how the field develops.”
Hauner says that it’s
too soon to say whether the technique might help patients. Scientists need to
test whether the fear memory could be weakened even more with longer sleep
times and whether the benefits last, she says.
CITATIONS
K. Hauner.
Stimulus-specific enhancement of fear extinction during slow-wave
sleep. Nature Neuroscience. Published online September 22, 2013. doi:
10.1038/nn.3527 Available online: [Go to]
SUGGESTED
READING
L. Sanders. Sleep
solidifies bad feelings. Science News. Vol. 181, February 25, 2012, p. 8.
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L. Sanders. Drug helps
put bad memories to rest. Science News. Vol. 182, November 17, 2012, p. 14.
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