When a person’s memory seems to change over time, scientists call it reconsolidation. One of Daniela Schiller’s colleagues, Marie Monfils, mentioned that, after behavioral training, a group of rats in one of her experiments seemed to lose their fear. This comment provided Schiller with what she describes as her “eureka moment.” Until then, memory reconsolidation had been blocked only by physical intervention, either drugs or electric shocks. If reconsolidation evolved so that memory could be augmented with new information, then behavior modification ought to have the same effect as a drug. “I suddenly realized that we had never tested that theory,” Schiller told Michael Specter. Monfils agreed to carry out a behavioral study of rats, and Schiller would do the same with humans.
The theory was borne out by both experiments. Schiller trained sixty-five people to fear a colored square by associating it with a shock. The next day, the sight of the square alone was enough to revive their fearful reactions. Then Schiller divided the subjects into three groups. By presenting the squares many more times, with no shock, she attempted to teach them to overcome their fear. That is called extinction training. The results were dramatic: people who saw the squares within ten minutes of having their memories revived forgot their fear completely. The others, who were not shown the squares again until hours later, remained frightened.
Schiller’s study, published in Nature in 2010, offered the first clear suggestion that it might be possible to provide long-term treatment for people who suffer from P.T.S.D. and other anxiety disorders without drugs. A year later, when the researchers tested the subjects again, the fear response still had not returned.
Schiller has been pursuing three central goals in her research:
• Tracing the neural mechanism, or signature, that causes memory to update in the human brain.
• Determining whether drugs might work safely in humans.
• Establishing a protocol that therapists could use to treat patients. (Scientists have already found that behavioral interference during reconsolidation appears to alter glutamate receptors in the amygdala, which might explain how memories are rewritten during the treatment.)
Schiller taught author Specter to fear a meaningless symbol: “Colored spheres began to float onto a computer screen in front of me, in no particularly discernible pattern: just a random, rapid-fire procession—purple, yellow, and blue. It didn’t take long to realize that nearly every time a blue sphere appeared a shock would follow; by the time I felt the voltage, my pulse and heart rate had already spiked in anticipation. The shock itself quickly became superfluous.”
The day after learning to fear the spheres, Schiller’s subjects see them again many times—but without the accompanying shock. ‘If you present a negative memory over and over again, without anything bad happening, it is possible for most people to overcome the fear,’ Schiller explained. Extinction training has for a long time been one of the principal treatments for phobias and fears; psychiatrists refer to it as exposure therapy. The more you see something, the less it scares you, and the less it scares you the more able you are to deal with it. See my blog on PTSD.
“There has always been a problem, though, in using extinction to treat people who have experienced profound trauma: the process leaves them with a pair of memories: blue sphere predicts shock; blue sphere doesn’t predict shock. Over time, the two memories can compete for expression. That is a significant characteristic of anxiety disorder. People will be fine for months or years, but if they encounter a particularly stressful situation the fear memory often overwhelms the calm memory.
“Schiller’s study demonstrated that the competing memories can become one. ‘If we zap it at just the right time, there are no new memories,’ she told me with a look of restrained satisfaction. ‘There is a different memory. You will still know what happened, and the information will be available to you. But the emotion will be gone.’”
This series of 3 blogs is based on the New Yorker article, “Partial Recall—Can neuroscience help us rewrite our most traumatic memories?” by Michael Specter May 19, 2014. Part I was mostly about memory and is the background for Part II. See Part III on August 12.
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