Friday July 13 2007
People can learn, with practice, how to forget painful memories, The Guardian and other newspapers reported. The newspaper reported that this could lead to “revolutionary therapies for people with emotional problems such as anxiety, depression, and post-traumatic stress disorder”.
The research behind this story was a study designed to investigate whether people could be trained to forget painful images and if the activity in different areas of the brain was linked to their success with this.
The study showed that volunteers could suppress memories of a distressing photographic image that they had been shown.
Our assessment is that this does not necessarily mean that people would be able to forget a distressing experience if it happened to them. We do not know whether similar results would be seen in people with anxiety, depression, or post-traumatic stress disorder.
Where did the story come from?
The study was a non-randomised experimental study carried out by Brendan Depue and colleagues from the Department of Psychology, at the University of Colorado, and published in the peer-reviewed journal Science.
What kind of scientific study was this?
Eighteen volunteers took part in this study where participants were shown 40 female faces with a neutral expression, each paired with a corresponding distressing image, such as a car crash. They were trained to remember these.
Participants were then shown 32 of the faces and asked either to remember or to suppress the corresponding image. Levels of brain activity were recorded by functional magnetic resonance imaging (fMRI, cross-sectional pictures of the brain showing levels of activity in each area of the brain). The researchers looked at how this response changed with increasing numbers of exposure to the images.
In the third part of the study, participants were shown each of the faces again, and asked to try to remember and describe the corresponding image. To test the participant’s general ability at recall, the eight of the original 40 faces that had not been shown in the second part of the study were also used. The researchers recorded how often people could recall images that they were told to think about and how many times they could remember images that they were told to suppress in the second part of the study. The researchers examined the levels of brain activity in different areas of the brain as each face was repeated.
What were the results of the study?
The researchers found that when recall was tested, volunteers could remember the distressing images more often if they had tried to think about them than if they had tried to suppress them.
When a participant was trying to suppress a painful image, there was increased activity in the prefrontal area of the brain, and decreased activity in the memory and emotional parts of the brain. The opposite was seen when a participant tried to remember an image.
Activity in different parts of the brain also varied over time as participants tried to suppress the image on repeated attempts.
What interpretations did the researchers draw from these results?
The researchers concluded that people can suppress distressing memories, and that the prefrontal cortex of the brain controls the ability to do this. They suggest that suppressing memories is a two-phase process. Initially one area of the prefrontal cortex (the right inferior region) suppresses the areas of the brain that are involved with the sensory aspects of memory. After this happens, a different area of the prefrontal cortex (the right medial region) suppresses the areas of the brain involved with memory processing and emotion.
They suggest that these findings “may have implications for therapeutic approaches” to conditions involving emotionally disturbing memories, such as post-traumatic stress disorder, phobias, obsessive compulsive disorders, ruminative anxiety and depression
What does the NHS Knowledge Service make of this study?
Although the underlying study reports convincing evidence that emotional memories are suppressed by circuits in specific areas of the brain, the link between this and future treatments for real people with these conditions is not clear. The lead scientist stated the group “hope the new findings and future research will lead to new therapeutic and pharmacological approaches to treating a variety of emotional disorders”.
This study is reliable scientifically; however, there are several limitations that must be considered when applying these results to real-life situations:
The study showed that volunteers could suppress memories of a distressing photographic image that they had been shown. This does not necessarily mean that people would be able to forget a distressing experience if it happened to them.
We do not know whether similar results would be seen in people with anxiety, depression, or posttraumatic stress disorder.
Without further research, we cannot draw conclusions on the efficacy of treatments aimed at suppressing emotion and memory, whether such treatments affect the same parts of the brain as in this study, or if they are helpful for any of the conditions mentioned.