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THURSDAY, Jan. 8 (HealthDayNews) -- Do you recall the last time you actively tried to forget something unpleasant? Maybe it was an embarrassing moment, or Britney Spears' weekend wedding that wasn't.

New research suggests your brain is quite busy when you take on the task of un-remembering. The process, in fact, is similar to the mental effort required to stop your arm or leg from moving.

"Maybe a lot of our forgetting is a bit more active than we are accustomed to believing," says University of Oregon neuroscientist Michael Anderson, co-author of a new study released today in the journal Science.

Scientists love to study how memory works, and psychologists endlessly noodle over what your memories -- or lack thereof -- reveal about your inner life. Despite all this, "we know much more about how the brain remembers information than how it forgets information," says Michael Platt, an assistant professor of neurobiology at Duke University.

In the new study, Anderson and his colleagues used magnetic resonance imaging (MRI) technology to examine the brains of 24 people. The people, all of various ages, were given pairs of words and told to remember some of the matched pairs but forget others.

"We found that trying to shut out memory was actually in some ways more demanding" than remembering, Anderson says. "Areas of the brain were significantly more activated when they tried to stop themselves from thinking of an unwanted memory."

During the tests, the MRI images revealed that the prefrontal cortex and hippocampus lit up during attempts at memory suppression. This suggests that the prefrontal cortex, which manages much of the brain, is telling the hippocampus -- a memory center -- what to do, Anderson says.

The process is similar to what happens when the brain of an animal tells its body to stop doing something. Communication between the prefrontal cortex and hippocampus also happens when people remember things, says Platt, who notes that amnesia occurs when the hippocampus gets damaged or destroyed.

Some people in the study were better at suppressing memories than others. The researchers could tell which ones did a better job just by looking at the MRI images to see whose brains were more active in the two regions, Anderson says.

"Some people are much more well practiced at shutting out unwanted memories," he says. "That's the kind of thing we're interested in learning more about. Obviously, not everyone can do that."

Some memories, of course, can never be erased and stay with people for a lifetime. But forgetting is an integral part of memory -- and for good reason, Platt says.

"Consider what would happen if you remembered everything," he adds. "Remembering everything might be nearly as disabling as total amnesia."

Platt notes that further research is necessary to better understand the act of forgetting.

And it's possible that researchers will one day be able to find new ways to help people who can't get rid of traumatic memories.

That will be one breakthrough not easily forgotten.

More information

Get tips on enhancing your memory from the Mayo Clinic or the Nemours Foundation.

(SOURCES: Michael Anderson, Ph.D., associate professor of cognitive neuroscience, University of Oregon, Eugene; Michael L. Platt, Ph.D., assistant professor of neurobiology, Duke University Medical Center, Durham, N.C.; Jan. 9, 2004, Science)

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