Monday, December 23, 2013

Erasing unwanted memories

Scientists have zapped an electrical current to people's brains to erase distressing memories, part of an ambitious quest to better treat ailments such as mental trauma, psychiatric disorders and drug addiction.

In an experiment, patients were first shown a troubling story, in words and pictures. A week later they were reminded about it and given electroconvulsive therapy, formerly known as electroshock. That completely wiped out their recall of the distressing narrative. ...

The 39 patients were asked to watch two distressing stories on a computer screen, narrated via a series of pictures and a voice-over. One story was about a child who is hit by a car and has to have his feet severed by surgeons. The other involved a pair of sisters, one of whom is kidnapped and molested.

A week later, the 39 patients were randomly assigned to one of three groups, A, B and C. Each person was prompted to recall details about just one of the troubling stories he or she had seen—an effort to specifically reactivate that memory.

Group A was given ECT immediately after. A day later, the patients took a multiple-choice quiz about both stories. They recalled most details about the particular story for which their memories hadn't been reactivated.

However, their recall for the other story—whose memory had specifically been reactivated—was extremely poor. It was no better than guesswork, in fact.

Patients in group B were given ECT immediately after, and their memories were tested immediately after the procedure. Their recall of both stories was intact. It suggests that it takes time to impair a memory—something the scientists had predicted.

The 13 members of group C acted as a control group and didn't receive ECT. When tested, their memories of the stories were actually enhanced. That suggests that it requires both reactivation and ECT to prevent reconsolidation and thereby disrupt memories in people.