The findings, to be published Jan. 9 in the journal Science, reinforce Sigmund Freud's controversial century-old thesis about the existence of voluntary memory suppression.
"The big news is that we've shown how the human brain blocks an unwanted memory, that there is such a mechanism and it has a biological basis," said Stanford psychology Professor John Gabrieli, a co-author of the paper titled "Neural Systems Underlying the Suppression of Unwanted Memories." "It gets you past the possibility that there's nothing in the brain that would suppress a memory that it was all a misunderstood fiction."
The experiment showed that people are capable of repeatedly blocking thoughts of experiences they don't want to remember until they can no longer retrieve the memory, even if they want to, Gabrieli explained.
Michael Anderson, a psychology professor at the University of Oregon and the paper's lead author, conducted the experiment with Gabrieli and other researchers during a sabbatical at Stanford last year.
"It's amazing to think that we've broken new ground on this that there is a clear neurobiological basis for motivated forgetting," Anderson said. "Repression has been a vague and controversial construct for over a century, in part because it has been unclear how such a mechanism could be implemented in the brain. The study provides a clear model for how this occurs by grounding it firmly in an essential human ability the ability to control behavior."
In recent years, the question of repressed memory has attracted considerable public attention concerning cases involving childhood sexual abuse. "That was very controversial because it went through two pendulum swings," Gabrieli said. "The first swing was that people thought, 'What a horrible thing.'
Contact: Lisa Trei