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Part of the Brain that Extinguishes Fear is Found
by Steven Reinberg - HealthDay News
The areas of the brain involved in learning fears have been
known, but new research now identifies the areas involved in
extinguishing those fears.
"We have been able to identify neural circuits of extinction
learning in humans," said study author Elizabeth Phelps, an
associate professor of psycology and neural science from New
York University. "This is important, because extinction is a
model we can use to look at how we get rid of fears we have
learned."
Phelps and her colleagues found that the area called the
amygdala is a key in both learning and unlearning fears.
They also found that the ventral medial prefrontal cortex is
critical for the long-term extinction of fears, according to
their report in the Sept. 16 issue of Neuron.
In their experiments, the researchers presented the subjects
with either blue or yellow squares. One color was associated
with a mild electric shock. Using this method, the subjects
acquired a fear of the colored square associated with the
shock.
Phelps' team then extinguished the fear response by
presenting the colored square associated with the shock,
first with a gradually reduced shock and then with no shock
at all.
To determine the brain areas involved, the subjects' brains
were scanned during the experiment by functional magnetic
resonance imaging, or fMRI, which uses harmless magnetic
fields and radio signals to measure blood flow in targeted
areas of the brain. These images reflect the level of brain
activity.
"We focused on the amygdala and the ventral medial
prefrontal cortex, because research in rats has shown that
these are important areas," Phelps explained.
"We found that the amygdala seems to play an important role
early on in extinction learning," she noted. Phelps said
there are drugs that target the amygdala, which help in the
treatment of anxiety disorders.
"The ventral medial prefrontal cortex seems to be more
important in retaining this extinction learning," Phelps
said. "Both of these regions are important for different
parts of the process."
These models for how fears are learned and extinguished are
being used to develop treatments for anxiety disorders,
Phelps added.
"(Understanding) these mechanisms and testing these
mechanisms in humans is going to help us develop effective
treatments for these disorders," she said. "It will also
help us understand what's going wrong when you have an
anxiety disorder."
"More and more research is focused on how we get rid of
fears and anxieties," Phelps said. "This is an example of
how we can take the kind of things we are doing in rats and
show that we are getting the same things in humans. It opens
up the possibility for us to translate these animal models
to human function and to human anxiety disorders."
"These findings do replicate what people are finding in
rats," said Jeffrey B. Rosen, an associate professor of
psychology at the University of Delaware. "There is a
relationship between the amygdala and the frontal cortex in
fear learning and extinction."
Rosen added these findings can be used to help develop
treatments for phobias and post-traumatic stress disorder.
"It looks like we can learn to extinguish these responses,"
he said.
- from HealthDay News, written by Steven Reinberg
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