We're still a far ways off from the kind of memory erasure portrayed in the film Eternal Sunshine of the Spotless Mind, but a recent experiment has just taken us one step closer. By using electroconvulsive therapy on depressed patients, scientists were able to disrupt their ability to recall emotionally jarring events.
Every time we recall a memory we have to take it out of our mental storage banks. According to theory, these memories have to be re-written back onto the brain's circuits each them they're accessed. It's an imperfect process called memory reconsolidation, and it's the crucial idea behind a recent experiment conducted by Marijn Kroes and his colleagues from Radboud University Nijmegen.
By using electroconvulsive therapy (ECT), which was once called electroshock therapy, the neuroscientists were hoping to disrupt this reconsolidation process. They wanted to disturb the re-formation of disturbing or unwanted memories in patients suffering from depression. In future, a more refined technique could be used to treat mental trauma, psychiatric disorders, and drug addiction.
For the experiment, Kroes took 39 patients who were undergoing ECT for severe depression (ECT works by passing electrical currents to parts of the brain, which triggers a brief seizure; patients are given muscle relaxants and an anesthetic). 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 patients were asked to recall details about one of the two stories (not both), after which time they were randomly sorted into three groups, A, B, and C (a control group).
Members of Group A and B were treated with ECT immediately following the retelling of the story. The following day, Group A participants had to complete a multiple-choice quiz about both stories. Fascinatingly, they did a better job recalling the story for which their memories hadn't been reactivated (or reconsolidated).
Their recall ability for the recounted story was no better than chance. Group B, on the other hand, had their memories tested about 90 minutes after the ECT, and their recall abilities were intact -- suggesting that it takes time to impair a memory. Group C did not receive ECT at all, and their recall abilities were solid, indicating that both ECT and reconsolidation is required to impair memory recall.
So this study furthers the memory reconsolidation theory. The technique could also prove useful for therapists -- albeit a very blunt one.
Read the entire study at Nature Communications: "An electroconvulsive therapy procedure impairs reconsolidation of episodic memories in humans."
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