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You can forget the past...
13/07/2007 07:22 - (SA)
Washington - Researchers have
confirmed what common wisdom has long held - that people can
suppress emotionally troubling memories - and said on Thursday
they have sketched out how the brain accomplishes this.
They said their findings might lead to a way to help
patients with post-traumatic stress disorder or anxiety to gain
control of debilitating memories.
"You're shutting down parts of the brain that are
responsible for supporting memories," said Brendan Depue, a
neuroscience doctoral student at the University of Colorado who
worked on the study. He said his team discovered the brain's
emotional centre is also shut down.
For their study, Depue and colleagues taught 18 adult
volunteers to associate pictures of human faces with pictures
of car crashes or wounded soldiers. They were then shown each
face a dozen times and asked to either remember or forget the
troubling image associated with each one.
When they worked to block a particular negative image, then
looked at the face one last time, they could no longer name its
troubling pair in about half of the trials, Depue and his
colleagues report in Friday's issue of the journal Science.
The researchers used a brain imaging method called
functional magnetic resonance imaging, or fMRI, which shows the
brain's activity in real time, to track what was going on in
the brain. They got usable data on 16 people.
In the test, parts of each volunteer's prefrontal cortex -
the brain's control centre for complex thoughts and actions -
were activated. This seemed to direct a decrease of activity in
the visual cortex, where images are usually processed.
The hippocampus, where memories are formed and retrieved,
and amygdala, the emotion hub, were later also deactivated.
Suppression therapy?
The research is still far from being translated to the
psychiatrist's office, Depue and others acknowledged.
"In the first place, the stimuli may be unpleasant, but
they are hardly traumatic," said the University of California
Berkeley's John Kihlstrom, who was not involved in the study.
"My prediction is it won't be as easy to suppress something
that's long-standing and personally emotional," Depue said.
People with post-traumatic stress disorder are often
troubled for decades by recurring images of a harrowing
experience.
Still, patients might practice blocking such memories out
of their minds, or at least reducing their emotional sting.
"It might be the case that people with memory disturbances
have to gain some control over the memory representation by
remembering it (and) trying a different emotional response to
the memory before successful suppression," Depue said.
A drug targeting specific brain regions might eventually
boost the ability to suppress, said John Gabrieli at the
Massachusetts Institute of Technology.
For a mother haunted by the memory of her son's suicide, he
said, "it is hard to imagine that you'd ever get her to forget
that the event occurred. (But) the more you could weaken the
memory in any dimension, the better it would be."
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