Remember the Rats—An Easy Way to Change Your Fear-Based Memories

Anisomycin as a protein synthesis inhibitor blocks consolidation of traumatic memories

By Peter M. Vishton, PhDWilliam & Mary
Edited by Kate Findley and proofread by Angela Shoemaker, Wondrium Daily

Systematic desensitization involves thinking about your phobia while in a relaxed state, which gradually reduces the fear response. More recent work suggests a way that the process might be accelerated. Professor Vishton explains.

Older man relaxed on sofa
Recalling a fearful memory while you are relaxed helps to desensitize you the intensity of the memory. Photo By fizkes / Shutterstock

Reconsolidation and Desensitization

This new work also has the potential to provide a much better understanding of how memory and fear actually function. This radical new treatment interferes with memory reconsolidation, changing our view of short-term and long-term memory. 

As in the traditional view, the idea remains that we perceive the world around us and pull that information into our short-term memory. Some of that information gets consolidated into our long-term memories. Later, when we want to remember something, we pull that long-term memory back into our short-term, working memory.

Here’s what’s different. The basic, older model presumes that what is moved to the working memory is a copy of the long-term memory, not the long-term memory itself. This recent research suggests that’s not correct.

The theory considers remembering something as being akin to checking the memory out of a library. You pull the memory into working memory and use it. When you’re done, you need to remake that long-term memory again. 

The initial transfer of information from short-term to long-term memory is called consolidation. This transfer from short-term memory back to the long-term memory library again is referred to as reconsolidation. 

If you don’t reconsolidate a memory—if you don’t remake it after recalling it—then the memory gets lost. The very process of remembering something might result in something being forgotten.

Rat Studies on Fear

The bulk of evidence for this reconsolidation phenomenon comes from studies conducted with rats. At the start of one of these experiments, rats learn an association between two stimuli—for example, a beep and a mild electric shock. 

Rats don’t like electric shocks, of course, so when they know that one is coming, they exhibit several characteristic behaviors. For example, rats stop drinking water when they anticipate shock. 

A rat in one of these studies would have a water bottle available. Whenever the rat is thirsty, it licks the end of the nozzle, and some water comes out. All of the rats in this study are thirsty when they start, so they all tend to exhibit a high rate of licking the water bottle.

If, while they are licking the bottle, a beep sound is played, followed two seconds later by a brief shock, the rats quickly learn this association. When the beep is played, the rats stop drinking. 

After a few dozen trials, they will do this even if the shock doesn’t occur after the beep a few times. The rats have learned to fear the beep.

If you wait 24 hours and test them again, the rats will still exhibit this reduction in drinking when you play the beep sound. The association is clearly stored in the rat’s long-term memory.

Neurons produce particular proteins when a new memory is being formed. If the synthesis of these proteins is blocked, then the brain can’t change its structure—it can’t form new memories. 

Anisomycin and Memory

Anisomycin is a drug that produces such an effect. If you were to inject a rat with anisomycin before the experiment, the association between beep and shock would be greatly weakened if not altogether absent.

The rats described here, though, have already learned this association. If you injected them with anisomycin, it won’t have any immediate effect. 

The rats already have the association encoded into their long-term memory. They won’t be able to form new associations, but the old ones will remain completely intact and still influence their behaviors just like it did before.

The key experimental group in one of these studies are rats who are both exposed to the beep and injected with anisomycin. For these rats, the beep signals a coming shock—they check that memory out of their long-term memory library. 

However, the anisomycin blocks the rats’ ability to remake the memory—to check it back into their long-term memory library—and reconsolidate it. For these rats, the association between beep and shock seems to vanish. 

If you later play the beep, they’ll tend to keep drinking as if the beep had never been paired with shock in the first place. They seem to have unlearned the association.

“Now, the way I’ve described this process of checking out memories and then checking them back in is a little oversimplified, but there is clear evidence that, when a memory is recalled from long-term memory back into working memory, that it’s placed in a state of flux, a state in which it can be changed—even erased,” Professor Vishton said.

The process sounds a bit like science fiction. In fact, several books and movies have expanded on this idea that a drug or other technology could erase memories. Philip K. Dick’s story “Paycheck” or the movie Eternal Sunshine of the Spotless Mind are two examples.

This article was edited by Kate Findley, Writer for Wondrium Daily, and proofread by Angela Shoemaker, Proofreader and Copy Editor for Wondrium Daily.
Image of Professor Peter Vishton

Peter M. Vishton is an Associate Professor of Psychology at William & Mary. He earned his PhD in Psychology and Cognitive Science from Cornell University. Before joining the faculty of William & Mary, he taught at Northwestern University and served as the program director for developmental and learning sciences at the National Science Foundation.