A Pill to Erase Bad Memories? Not Quite…

I heard it during a news commercial during House, “a pill to remove bad memories.” I thought, “I should watch that. It sounds too good to be true,” but I didn’t. Then I see the headline in The Huffington Post, Pill to Erase Bad Memories: Ethical furor over drugs “that threaten human identity and I knew I had to check this out because it sounded too good to be true. And it is.

The research article that the news media is mangling is a study from the University of Amsterdam by Kindt, Soeter, and Vervliet (2009), Beyond extinction: Erasing the human fear response and preventing the return of fear published in Nature Neuroscience. (Actually, it’s pre-press.) In this experiment, the authors performed a double-blind test in which they first stimulated a fear response to spiders by pairing images of spiders with electric shocks. On the second day, they gave the control group a placebo and the experimental group propranolol, a β-adrenergic receptor antagonist, or beta blocker, and re-exposed them to the spiders, measuring potentiation of the eye blink startle reflex to a loud noise as a test of fear response. What they found was that subjects given propranolol were calmer and less likely to startle. On the third day the researchers attempted the startle test again after the beta blocker was gone from the system and found that the subjects stayed calm.

As an extra test, they tried just giving beta blockers without reintroducing the fear response. Those subjects remained fearful, so it appears that the mechanism only works by combining the drug with exposure.

Beta blockers block androgens like testosterone, which are implicit in the fight or flight response.

What this treatment apparently does, and more studies are certainly warranted for a finding of this magnitude, is to remove the fear response that is paired with a particular memory. What it certainly does not do is “erase bad memories.” The researchers are clear on this:

Notably, the propranolol manipulation left the declarative memory for the acquired contingency between the conditioned and unconditioned stimulus intact, but this knowledge no longer produced emotional effects. Our finding that propranolol eliminated the fear response, without affecting declarative memory, is consistent with the observed double dissociation of fear conditioning and declarative knowledge relative to the amygdala and hippocampus in humans (Kindt, Soeter, & Vervliet, 2009, p. 3).

However, it appears that not everyone bothered to read the article:

Paul Farmer, chief executive of the mental-health charity Mind, said he was concerned about the ‘fundamentally pharmacological’ approach to problems such as phobias and anxiety.

He told Channel 4 News that the unintended consequences ‘could include the eradication of positive memories’.

Not quite, because it doesn’t eradicate memories.

I am not a neuroscientist. Reading neuroscience is a bit of a hobby, but I am by no means an expert. However, I think it would be fair to say that there are different mechanisms in the amygdala to pair memories with different emotions. And it wouldn’t be too far of a stretch to believe that a drug may affect one aspect (say, fear) without affecting another (happiness). Also, remember that we don’t know the mechanism behind this yet. The authors propose that beta blockers affect the amygdala, the brain’s emotion center, but not the hypocampus, where facts and events are stored. The amygdala is also active in the process of learning, and that might have something to do with the mechanism of action. But the key point is that no one is advocating throwing this treatment out there without adequate testing. If they do find it effective with low side effects, this could be a major breakthrough. After all, every talking therapy is essentially trying to do this: remove the fear response from a patient’s memory of feared events and trauma.

The Internet is wonderful for science news, but it is hard to differentiate the real story from the media’s version. It took three articles before I found the source of this story and was able to read the evidence for myself. If you find something that looks too good to be true, try to do a little digging.

UPDATE: Ed Young over at Not Exactly Rocket Science got to this story and tore the media’s version apart before I was out of bed this morning. Unfortunately, I didn’t see it. Credit where credit is due.

Merel Kindt, Marieke Soeter, Bram Vervliet (2009). Beyond extinction: erasing human fear responses and preventing the return of fear Nature Neuroscience DOI: 10.1038/nn.2271