OT: Scientists find way to block fearful memories
computeruser
Wed, Dec 9 2009
By Julie Steenhuysen
CHICAGO (Reuters) - U.S. researchers have found a drug-free way to block
fearful memories, opening up the possibility of new treatment approaches for
problems such as post traumatic stress disorder, they reported on Wednesday.
The findings in people build on studies in rats that showed that
reactivating a memory -- by showing people objects that stimulate the
fearful memory -- opens up a specific time window in which the memory can be
edited before it is stored again.
"Before memories are stored, there is a period where they are susceptible to
being disrupted," said Elizabeth Phelps of New York University, whose study
appears in the journal Nature.
Earlier studies have shown that drugs can be used to block fearful memories,
but the results were not long lasting.
Phelps and colleagues based their studies on findings in rats that showed
that old memories can be changed or reconsolidated, but only during a
specific window time after the rat is reminded of the fearful memory.
That window of susceptibility is typically between 10 minutes after
re-exposure to the object to 6 hours later, when the memory stored once
again in the brain.
The researchers applied these findings to people in a lab setting. First,
they created a fearful memory by showing the volunteers a blue square, and
then delivering a mild shock.
Once they had created the fear memory, they simply showed a blue square,
which reminded them of the fear memory.
The team waited 10 minutes and then started a training period where the
volunteers were repeatedly exposed to the blue square without a shock.
Phelps said simply delaying the exposure training so that it falls within a
period during which the memory is susceptible to being edited made a lasting
difference in the ability to block the fear memory.
A second group that was exposed to the blue square without the 10-minute
waiting period, continued to show fear when exposed to the blue square.
When they brought people back a year later, the group that got the training
showed no fear response -- tracked by changes in the skin -- when exposed to
the blue square, while other volunteers continued to have a fear response.
Phelps said the important aspect of the study is the time window.
"What we think is happening is because we did it at the right time, you are
restoring the memory as safe as opposed to just creating a new memory that
competes with the old memory," Phelps said.
She said the findings are the first of their type in humans, and she
cautioned that the findings cannot be immediately applied to people with
severe anxiety problems, such as post traumatic stress disorder.
"We did a blue square with a mild shock," she said. "Normal fear memories
are way more complex than that."
But she said, the findings do open up the possibility of new training
methods that can be studied to help people overcome difficult memories.
"It's really exciting for the potential of treating these disorders. It's
just a ways away," Phelps said.
The study was supported through a grant by the National Institutes of
Health's National Institute of Mental Health.