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A focus on forgetting memories too painful to remember Scientists are examining the potential advantage of discarding recollections -- and ways to bring it about.

By Martin Miller, Times Staff Writer

From rituals of remembrance to Post-it notes, humans struggle to preserve memories. And no wonder. They are, after all, at the core of personal identity.

Sometimes overlooked in the rush to remember, however, is the value of forgetting. Though the research is in the early stages, scientists are investigating the process, necessity and potential advantages of discarding recollections.

"We'd be absolutely lost without our ability to forget," said Michael Anderson, an associate professor of cognitive neuroscience at the University of Oregon. "Just on a basic level, can you imagine if you couldn't constantly update your memory? Do you want 10 years worth of parking space memories and all your old phone numbers in your head?"

Much of the research is focused upon helping us deliberately forget specific events. Two methods -- behavior changes and drugs -- have proved at least moderately successful, suggesting that certain memories can indeed be cast off. The benefits of perfecting such techniques are enormous, say researchers. Combat veterans, abused children, car crash victims, to name a few, could all be freed from severe emotional trauma by eliminating the offending memory, or at least the emotional pain associated with it, say researchers.

"We want to be able to keep the past from overly intruding on a patient's life," said Roger Pittman, a professor of psychiatry at Harvard Medical School, who has worked extensively with victims of post-traumatic stress disorder (PTSD). "When it preoccupies someone so much they can't concentrate on their work, their families, their present lives, it can ruin them."

Pittman's research found that emergency room patients who were given beta blockers within six hours of a traumatic event were far less likely to develop PTSD than those who did not. The treatment shows promise, Pittman believes, because the medication interferes with the brain's ability to properly establish a deeply embedded memory. The research was published last year in the Journal of Biological Psychiatry. "The best outcome we can hope for now is that when they remember the event, they take it in stride, that it doesn't cause the upheaval it does now," said Pittman. "It's a form of emotional forgetting."

Unwanted memories

Cracking the code of traumatic memory storage poses one of the greatest challenges for researchers. Studies have shown that stressful events release powerful hormones inside the brain that ensure the episode will be vividly recalled. The more stressful, the more hormones flood the brain. From an evolutionary standpoint, the response is critical for survival, researchers say.

"That's why we can't remember where we were the morning of Sept. 10," said Pittman, "but can on the morning of Sept. 11."

Behavior changes show promise as well in efforts to block unwanted memories. A University of Oregon study found that students could actually learn to obstruct selected memories, thus supporting a century-old assertion by Sigmund Freud that humans are equipped with a memory repression mechanism.

Students were first asked to memorize pairs of words in which the first word would be a rough trigger to recall the second, such as "ordeal" and "roach." Then, subjects were encourage to forget the second word. One group tried to do this by thinking about the word and saying it aloud, while another group was told to repress the word.

Trying to forget

The study had surprising results, said Anderson who is examining brain structures during voluntary forgetting. The group that was constantly reminded of the word could forget it, and the one that tried to obliterate the memory failed, even when offered extra money to do so.

"Amazingly, this type of forgetting is more likely to occur when people are continuously confronted with reminders to the very memory they are trying to avoid," said Anderson who believes the dynamic is in action on a national level regarding images of the World Trade Center.

"This is quite contrary to intuition. It's not enough to want to forget something. You have to want to forget it and be forced to confront reminders of it."

Such research is in its infancy, however, and scientists have trouble agreeing on even the most basic propositions.

What does it mean to forget? Can an experience truly be forgotten or does it simply lack the proper stimulus to come thundering back to the conscious mind?

"It's very difficult to prove someone has permanently forgotten things as opposed to being unable to recall it," said Anderson.

Some research into the nature of forgetting has lead to unexpected finds. Larry Cahill of the Center for the Neurobiology of Learning and Memory at UC Irvine has discovered that men and women process traumatic events in vastly different ways.

For reasons still unknown, women are twice as likely to experience PTSD as men even though they've gone through the same painful episode.

"This is all pretty brand-new stuff," said Cahill, an assistant professor of neurobiology and behavior. "The field is going to have to sift through this. We're really a baby crawling in diapers, we're making good progress, but there's far more that we don't know than we do."