Publication Date: Wednesday, February 11, 2004
Forgetting the past
Forgetting the past
(February 11, 2004) Stanford researcher shows there's a way to block unwanted memories
by Elizabeth White
From embarrassing experiences -- like the time you fell on the playground in front of your classmates in third grade -- to more traumatic events, such as a mugging or kidnapping, we all have times in our lives we would like to forget.
And just when one wants not to think about such a memory, it seems to be the first thing that comes to mind.
But now researchers at Stanford University and the University of Oregon have found that humans do have the biological ability to block unwanted memories.
John D. E. Gabrieli, a Stanford professor of psychology, co-wrote the paper, "Neural Systems Underlying the Suppression of Unwanted Memories," with lead author Michael C. Anderson, a University of Oregon professor of psychology. The paper appeared in the Jan. 9 issue of the journal "Science."
"It's a longstanding question of intrigue about whether you can really get rid of memories," Gabrieli said. Sigmund Freud, he noted, was one of the first to pose the question when he explored hysteria in women and asked if repressed childhood memories were causing problems in adulthood.
Anderson picked up the topic in a 2001 paper he wrote about how to study memory suppression. The research, he said, revolves around "that moment where you go, 'I don't want to think about that.'"
What Gabrieli, Anderson and other researchers found was that not only can people not think about a memory, but they can actually forget it after a time.
"We imagine this suggests that there's a healing capacity," Gabrieli said.
In the study, participants studied pairs of unrelated nouns. They were tested on the pairs until they memorized most of them. Then they underwent an MRI scan of their brains.
During the MRI, the subjects were given the first word in a pair and told to actively think about the second word. They did so for 12 pairs. They were then shown 12 more first words and asked to not think about the other word in the pair. The participants were briefly shown a third set of 12 pairs, which served as the "baseline" group.
After the scanning, the subjects were retested on all 36 pairs. The researchers found the subjects had a harder time remembering the pairs they had actively tried not to think about than the baseline pairs they hadn't been exposed to for 30 minutes.
The researchers' conclusion?
"I think that it emphasizes that repression really works," Gabrieli said.
The MRI scans showed telling phenomena going on in the brain's frontal cortex, which controls thinking, and hippocampus, which is essential for remembering experiences, he said. Essentially, the more active the frontal cortex and the less active the hippocampus, the better people suppressed memories.
Memory suppression is akin to stopping physical action, Anderson said, like starting to catch a falling plant but stopping when you realize it's a cactus. In fact, the brain uses many of the same regions to stop physical action as it does to stop memory retrieval.
"We absolutely, positively need to do this," he said of suppressing physical action. "It's an adaptive ability. Maybe we can stop internal actions, too."
"This (research) provides an existence proof," he added. "I think the work needs to be taken further to establish that these processes are effective for emotional memories."
Indeed, the research was narrowly tailored and modest in scope, involving neutral word pairs and 24 voluntary participants Gabrieli said. It also only involved a half-hour of repression rather than years and years of forgetting.
Still, the results may provide help for the future study of truly traumatic experiences, specifically post-traumatic stress disorder and war veterans' flashbacks, Gabrieli said. Generally, the ability to suppress can be a positive coping mechanism, so long as it isn't done in excess, he said.
"We imagine it would be far more of an upside than a downside," he said. "It's sort of like eating. It's good to eat, (but) eating unhealthy things or too much is not good."
The experiment may also have some ramifications in the study of hypnotism.
Dr. David Spiegel, a professor in Stanford's department of psychiatry, is interested in pursuing research as to whether the brain, when under hypnosis, is acting in the same way it does during the process of memory suppression.
"Nobody has shown that that pathway works with hypnotic suppression of memory, but it's possible," Spiegel said. "When (hypnotized) people are acting on an instruction not to remember, the brain is acting like it really can't remember. We see with hypnosis that people change what they see."
The paper's other authors were Kevin N. Ochsner, a former Stanford postdoctoral fellow now at Columbia University; Stanford researchers Brice Kuhl, Jeffrey Cooper and Elaine Robertson; science and engineering associate Susan W. Gabrieli; and radiology professor Gary H. Glover.
Elizabeth White can be reached at lwhite@paweekly.com
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