Theories suggest that every time we recall a memory we have to take it out of our mental storage banks. These memories have to be re-written back onto the brain's circuits each them they're accessed.
The crucial idea behind a recent experiment, conducted by Marijn Kroes and his colleagues from Radboud University Nijmegen, is an imperfect process of recalling the memories, called memory reconsolidation, Discovery News reported.
The neuroscientists hoped to disrupt this reconsolidation process by using ECT, also known as electroshock therapy.
They wanted to disturb the re-formation of disturbing or unwanted memories in patients suffering from depression.
For the experiment, Kroes took 39 patients who were undergoing ECT for severe depression. Each patient was asked to watch two rather upsetting videos, one about a child who is hit by a car and has to have his feet severed by surgeons, the other involving a pair of sisters, one of whom is kidnapped and sexually assaulted.
A week later, the researchers asked the patients to recall details about one of the two stories, after which time they were randomly sorted into three groups, A, B, and C (a control group).
It was found that members of Group A and B, who were treated with ECT immediately following the retelling of the story, did a better job recalling the story for which their memories hadn't been reactivated.
On the other hand, recall abilities of Group C, which did not receive ECT at all, were solid, indicating that both ECT and reconsolidation is required to impair memory recall.