Jan 11 2004
Research reveals for the first time the biological mechanism that the brain uses to block unwanted memories. The study, published in the journal Science, demonstrates how unpleasant memories can be repressed.
Psychology Professor John Gabrieli, a co-author of the study, is quoted in a Stanford University press release as stating "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. 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."
Michael Anderson, the paper's lead author, summarized the results this way: "It's amazing to think that we've broken new ground on this … that there is a clear neurobiological basis for motivated forgetting. 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."
The issues surrounding "repressed memories" and "false memories" are complex. Studies have demonstrated that both sorts of memories can be created in the laboratory. We are less certain what this means when confronted with a newly emerged memory of childhood abuse.
In the current study, twenty-four volunteers aged 19 to 31 were given 36 pairs of unrelated nouns, such as "bicycle-roach," and asked to remember them at 5 second intervals. They were tested on memorizing the pairs until they got about three-quarters of them right. They were then tested while having their brains scanned using functional magnetic resonance imaging (fMRI).
The researchers randomly divided the 36 word pairs into three sets of 12. In the first set the subjects were asked to look at the first word in the pair (presented by itself) and recall and think about the second word. In the second set, subjects were asked to look at the first word and not recall or think of the second word. The third set of pairs served as a baseline and was not used during the brain scanning part of the study.
Subjects were then retested on all 36 word pairs. They remembered fewer of the word pairs they had actively tried to not think of than the baseline pairs, even though they had not been exposed to the baseline group for 30 minutes.
The fMRI results showed that controlling unwanted memories was associated with increased activation of the left and right frontal cortex. This led to reduced activation of the hippocampus (one part of the brain associated with memory). The more subjects activated their frontal cortex during the experiment, the better they were at suppressing unwanted memories.
Clearly we can repress unwanted memories. The fMRI results are interesting, since they confirm that the brain areas involved are the ones that we might predict would be involved. Studies like this should silence those who take the extreme position that memories can't be repressed. It does not address whether repressed memories that are later recovered are true.
Last updated 11/6/05
