Confessions

Everyone has painful or unpleasant memories in their past, and some of us would welcome the chance to forget them forever. Some debilitating disorders, like post traumatic stress disorder (PTSD), prey on these memories in ways that are often difficult-to-treat. According to some recent research, a drug taken shortly after a traumatic event, or during the recall of traumatic memories, may act to ‘erase’ them from the brain. Does it work, and could it be a useful treatment? What about the potential for abuse (“de-briefing” comes to mind)?

One drug, propranolol, is currently used to treat hypertension, but it has also already been shown to weaken memories of a traumatic experience when given shortly after the event. Propranolol is a beta-blocker: it blocks the action of epinephrine on both β1- and β2-adrenergic receptors (which may block the formation of frightening memories in the amygdala). However, new research from McGill University suggests that this drug may also act on memories in a retro-active way: if propranolol is given while subjects are asked to recall traumatic memories that occured up to 10 years ago. Interestingly, the result is that the emotional content of the memories are drained, without completely ‘wiping the slate clean,’ so to speak. The subjects remember what occurred, but in a factual rather than emotionally-affecting way.

The experiments are being done [at McGill] involve people traumatized as long as 20 or 30 years ago by child abuse, sexual assault or a serious accident.

“It’s amazing how a traumatic memory can remain very much alive. It doesn’t behave like a regular memory. The memory doesn’t decay,” Brunet said.

To try to make it decay, researchers ask people to describe the trauma as vividly as they can, bringing on physical symptoms like racing hearts, then give them propranolol to blunt “restorage” of the memory. As much as three months later, the single dose appears to be preventing PTSD symptoms, Brunet said.

“Each time you retrieve a memory it must be restored,” he said. “When you activate a memory in the presence of a drug that prevents the restorage of the memory, the next day the memory is not as accessible.”

In another study by Joseph LeDoux’s team at NYU, it was shown possible to eliminate a single memory in rats using a different drug, U0126. This occured without affecting any other memories that the rats had, but questions remain as to whether the ‘deletion’ is permanent. The group is now enrolling subjects for a human study.

Most people, including the researchers in these studies, readily admit that fearful memories do serve some purpose. They remind you to avoid certain harmful stimuli or situations, and perhaps play a role in the formation of personalities and tastes. However, such memories may be moot when it comes to experiences far removed from normal life, like war or rape.