How the brain blocks memories

Experts have discovered how the human brain is able to suppress unpleasant memories and have succeeded in training people to block memories at will. Anya Weimann reports.

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SYDNEY: Experts have discovered how the human brain is able to suppress unpleasant memories and have succeeded in training people to block memories at will.

The finding may have implications for developing new therapeutic approaches to treating depression, anxiety and post-traumatic stress disorder.

“We have shown in the study that individuals have the ability to suppress specific memories at a particular moment in time through repeated practice,” said neuroscientist Brendan Depue of the University of Colorado in Boulder.

“We think we now have a grasp of the neural mechanisms at work, and hope the new findings… will lead to new therapeutic and pharmacological approaches to treating a variety of emotional disorders,” he said.

Disturbing images

Depue is lead author of a study, published in the U.S. journal Science, which identifies a two-step suppression process linked to the prefrontal region of the brain.

The concept of memory suppression has been a controversial one among psychologists for a century. Now, to test the concept more rigorously, brain scans were used to show that volunteers who have been asked to banish disturbing memories show very specific patterns of brain activity.

Trying to forget: The researchers examined fMRI images of the memory-ruling part of the brain – the prefrontal cortex. – Science

For the purpose of the experiment, 16 volunteers were given 40 pairs of photographs to study. In each case, an image of a neutral human face was paired with an emotionally disturbing image such as a car crash, a wounded soldier, an electric chair or a violent crime scene.

After memorising each pair, the volunteers were placed in an fMRI (functional magnetic resonance imaging) scanner. Once inside the machine, they were shown only the neutral face images and instructed to either actively recall the associated image or to actively suppress it.

Brain mechanism

The results of the scans indicated that the volunteers were able to exert some control over their emotional memories.

“Our research demonstrates that when an individual attempts to suppress a memory, brain regions supporting the memory are actually shut down,” said Depue.

“In addition, we show that the frontal lobes, which are involved in planning and guiding behaviour, are responsible for this shut down. This provides the intriguing possibility that there may be a specific brain mechanism for suppressing memories,” he added.

“It looks to be an excellent study and certainly adds good scientific evidence from the field of integrative neuroscience supporting the possibility of memory suppression,” commented Richard Clark director of the Cognitive Neuroscience Laboratory at Flinders University in Adelaide, Australia.

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