According to Richard A. Friedman, a professor of clinical psychiatry and the director of the psychopharmacology clinic at the Weill Cornell Medical College, writing in Sunday’s New York Times, “Who among us hasn’t wanted to let go of anxiety or forget about fear?”
Phobias, panic attacks and disorders like post-traumatic stress are extremely common: 29 percent of American adults will suffer from anxiety at some point in their lives. “Sitting at the heart of much anxiety and fear is emotional memory — all the associations that you have between various stimuli and experiences and your emotional response to them. Whether it’s the fear of being embarrassed while talking to strangers (typical of social phobia) or the dread of being attacked while walking down a dark street after you’ve been assaulted (a symptom of PTSD), you have learned that a previously harmless situation predicts something dangerous,” says Friedman.
The current standard of treatment for such phobias revolves around exposure therapy. This involves repeatedly presenting the feared object or frightening memory in a safe setting, so that the patient acquires a new safe memory that resides in his brain alongside the bad memory. As long as the new memory has the upper hand, his fear is suppressed. But if he is re-traumatized or re-exposed with sufficient intensity to the original experience, his old fear will awaken with a vengeance.
“This is one of the limitations of exposure therapy, along with the fact that it generally works in only about half of the PTSD patients who try it. Many also find it upsetting or intolerable to relive memories of assaults and other traumatizing experiences.” New research, published recently in the journal,Biological Psychiatry, 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.
The author, Merel Kindt, a professor of psychology at the University of Amsterdam, and colleagues, 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.
Friedman writes, “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 touch the tarantula within days and, by three months, many 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. “These studies suggest that someday, a single dose of a drug, combined with exposure to your fear at the right moment, could free you of that fear forever. 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.”
By blocking the effect of norepinephrine and disrupting memory reconsolidation, we could perhaps reverse this process. The clear implication of these studies is that emotional memory is not permanent after all.