(Reuters)
Updated: 2007-07-13 09:47

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 center 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 center 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."