Practice Forgetting and Memories Fade

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Practice Forgetting and Memories Fade

 

By Michael Smith, Senior Staff Writer, MedPage Today

Reviewed by Zalman S. Agus, MD; Emeritus Professor at the University of

Pennsylvania School of Medicine.

July 12, 2007

 

BOULDER, Colo., July 12 -- With practice, people can learn to suppress emotional

memories, researchers here found.

 

Their study may have clinical implications for those suffering from

post-traumatic stress syndrome or obsessive-compulsive disorder, Brendan Depue,

a doctoral candidate at the University of Colorado, and colleagues reported in

the July 13 issue of Science. And it may also re-ignite the debate over

so-called repressed memories, a topic that has been highly controversial in

recent years. The process of suppressing a memory has two stages and is

under the control of the prefrontal regions of the brain, the researchers noted.

To test the degree to which people could suppress specific memories, the

researchers first trained 16 participants to associate 40 neutral images of

human faces with more emotion-laden pictures, such as a car crash or a wounded

soldier. After they memorized the pairs of images, the volunteers were

placed in magnetic resonance imaging scanners. Then they were shown 32 of

the faces 12 times each in a pseudo-random order.

For some pictures they were told to think about the associated disturbing

image, for others, they were told not to think about it. The remaining eight

pairs of faces and images were used as a baseline. The use of the cue

image only ensured that the subjects had to mentally manipulate their memory of

the other image, Depue and colleagues said. In the testing phase of the

experiment, they were shown all 40 cue images and asked to give a short

description of the associated image. Analysis found that on average the

volunteers were able to recall 62.5% of the pairs in the baseline group,

compared with 71.1% of those they were asked to think about and 53.2% of those

they were told not to think about. Recall was significantly different for

the " think " and not-think " groups (at P=0.0006), the researchers found. That was

because, compared to the baseline, there was a trend toward better recall in the

" think " group and significant reduction of recall (at

P=0.02) in the " not-think " group. The functional MRI scanning showed

that two regions of the prefrontal cortex are involved one after the other in

suppressing memories, the researchers said. First, the right inferior

frontal gyrus suppresses regions that support the sensory components of the

memory, including the visual cortex and the thalamus. Next, the right

medial frontal gyrus suppresses regions, including the hippocampus and amygdala,

that support emotional components of the memory. The results are

consistent with " the operation of an active process of suppression " of memory,

the researchers said. " By essentially shutting down specific portions of

the brain, [volunteers] were able to stop the retrieval process of particular

memories, " Depue said. " We think we now have a grasp of the neural

mechanisms at work, " Depue said, adding that he and his colleagues " hope the new

findings and future research will lead to new therapeutic

and pharmacological approaches to treating a variety of emotional disorders. "

Not everyone sees the upside to the study. Commenting on the results,

memory researcher Elizabeth Loftus, Ph.D., of the University California at

Irvine, fears that the research will be misused as support for the idea that

people can " banish horrific brutalization into the unconscious, " a notion she

has challenged for years. " This will be used as a supposed piece of proof

that [memory] repression has been discovered in the brain, " she said. " This is

not evidence for that but people will try to pretend that it is. " Pamela

Freyd, Ph.D., executive director of the False Memory Syndrome Foundation in

Philadelphia, noted that the images used in the experiment, while disturbing,

were not personally traumatic to the volunteers, so " the results are not at all

surprising to me. " But memories of real trauma can be " intrusive and

worrisome " and difficult to avoid thinking about,

she said. Depue agreed that personal trauma may be a different kettle of

fish. " A person could need thousands of repetitions of training to suppress such

memories, " he said. " We just don't know yet. "

 

 

The study was supported by the University of Colorado at Boulder. The authors

made no declaration with respect to potential conflicts.

 

Additional General Psychiatry Coverage

 

Primary source: Science

Source reference:

Depue BE et al. " Prefrontal Regions Orchestrate Suppression of Emotional

Memories via a Two-Phase Process. " Science 2007;317:215-19.

http://www.medpagetoday.com/Psychiatry/GeneralPsychiatry/dh/6146

 

 

" A trail blazed by an elephant becomes a roadway. " Burmese proverb

 

" The care of the Earth is our most ancient and most worthy, and after

all our most pleasing responsibility. To cherish what remains of it and to

foster its renewal is our only hope. " Wendell Berry

 

 

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