In the 2004 film Eternal Sunshine of the Spotless Mind, a character played by Jim Carrey visits an eccentric scientist who wipes out the bad memories of his relationship with Kate Winslet's character using a machine that maps their location in his brain and systematically deletes them. The concept might have seemed preposterous, but today scientists are reporting that a common blood pressure drug can produce a similar effect – not by destroying a memory itself, but by wiping out your fearful reaction to it.

Dutch scientists taught a group of 60 people to fear a spider by mildly shocking their wrists when they showed them a picture of the arachnid. Then, the next time the group were shown the spider, half were given propranolol (a beta-blocker prescribed to lower blood pressure and treat migraines in children), and half a placebo. Those who got the drug didn’t show any strong startle response to the spider, while those who got the placebo continued to have a significant one, according to the research in today’s Nature Neuroscience.

“The potential might be that we have a procedure that reduces irrational fears permanently,” study co-author Merel Kindt, a University of Amsterdam psychologist, told Bloomberg News, adding that people with post-traumatic stress disorder could benefit. “This combination of giving the drug at the moment that you reactivate the memory, you disrupt the memory trace.”

Kindt didn’t immediately respond to an email and phone message this morning about why propranolol seems to mute fear. But because propranolol lowers blood pressure and heart rate, musicians have been using the drug off-label for at least a decade to get over their stage fright. As we noted in last year's Ask the Experts piece about why Olympic athletes might take propranolol, the drug blocks the action of adrenaline, which is responsible for physiological effects including high blood pressure and rapid heart beat – two signs of fear. In the case of recall, propranolol may work by blocking the pathways by which those symptoms become linked to a specific memory.

It's not practical to give everyone who's about to experience something frighteningly memorable a beta-blocker, since scary events aren't necessarily predictable. But Harvard scientists tested propranolol in a pilot study of people who’d been in car accidents or assaulted, and found that those who had taken the drug within hours of the trauma showed none of the typical signs of PTSD (like sweaty palms, elevated heart rates and twitchy muscles) three months later when they listed to audiotapes of themselves describing their experience, the scientists reported in 2002 in Biological Psychiatry. The researchers are expected to complete a late-stage clinical trial of the treatment in May.

"The object of these drugs is not to make people forget their traumatic experiences," the Harvard scientist leading the trial, Roger Pitman, told the Harvard Gazette in 2004, "but to reduce the intensity of the memories to a more normal level, a level that a person can easily live with."

Image © iStockphoto/Diane Diederich