Friday, January 22, 2016

How to erase fear

New research suggests that it may be possible not just to change certain types of emotional memories, but even to erase them. We’ve learned that memories are uniquely vulnerable to alteration at two points: when we first lay them down, and later, when we retrieve them.

Merel Kindt, a professor of psychology at the University of Amsterdam, and her colleagues have seemingly erased the emotional fear response in healthy people with arachnophobia. For a study published last month in the journal Biological Psychiatry, she compared three groups made up of 45 subjects in total. One group was exposed to a tarantula in a glass jar for two minutes, and then given a beta-blocker called propranolol that is commonly prescribed to patients for performance anxiety; one was exposed to the tarantula and given a placebo; and one was just given propranolol without being shown the spider, to rule out the possibility that propranolol by itself could decrease spider fear.

Dr. Kindt assessed the subjects’ anxiety when they were shown the spider the first time, then again three months later, and finally after a year. What she found was remarkable. Those who got the propranolol alone and those who got the placebo had no improvement in their anxiety. But the arachnophobes who were exposed to the spider and given the drug were able to hold the jar containing the tarantula on Day 1 and, by three months, felt comfortable holding the spider with their bare hands. Their fear did not return even at the end of one year.

How does this work? Well, propranolol blocks the effects of norepinephrine in the brain. This chemical, which is similar to adrenaline, enhances learning, so blocking it disrupts the way a memory is put back in storage after it is retrieved — a process called reconsolidation. ...

But there’s a flip side to this story about how to undo emotional learning: how to strengthen it. We can do that with drugs as well, and may have been doing it for some time.

Anxiety enhances emotional memory. We all know that — it’s why you can easily forget where you put your wallet, but will never forget being attacked. This is the case because anxiety leads to the release of norepinephrine in the brain, which, again, strengthens emotional learning. It is also why we should think twice about casually prescribing stimulants like Ritalin and Adderall for young people who really don’t need them. Stimulants also cause the release of norepinephrine and may enhance fear learning. So it is possible that taking stimulants could increase one’s risk of developing PTSD when exposed to trauma.

Indeed, a study that will be published next month found that the escalating use of stimulants by the military in active duty soldiers, including those serving in Iraq and Afghanistan, was strongly correlated with an increase in the rates of PTSD, even when controlling for other factors, like the rate of attention deficit hyperactivity disorder.
--Richard A. Friedman, NYT, on remixing memory