Erasing fear memories [MUSIC PLAYING] DANIELA SCHILLER: In everyday life, we have all sorts of fears. And my personal experience with fear is parachuting. I did it several times, and I discovered it's very scary. But then I got interested in how you overcome fear. And my line of experiments deals exactly with that, how we overcome fear, how we change fear. And the particular experiment we just published, "Knowing Nature," is about preventing fear altogether, preventing it from returning. - In this experiment, we studied a very simple type of fear learning where we present you with a neutral stimulus, like a yellow square, and we pair it with a shock. After a few pairings, your body elicits a fear response. We measure this by measuring the skin conductance response. - Ow. - OK. That was enough. - OK. DANIELA SCHILLER: And you can see the response on the computer. That's-- that's a very strong response. - It's really just the electrical conductivity of your sweat glands, and that's just part of the natural arousal response you would have with fear. What we can do, though, we can get rid of that fear now just by presenting the yellow square over and over and over again and have nothing bad happen. Eventually you're going to learn that the yellow square doesn't predict shock, and I'm not going to see this fear response in your body. This is called extinction. And it works pretty well. It's the basis for treatments for phobias. The problem with that type of learning is that what we've done, and we know this from a lot of behavioral studies in humans and other species, is we've created two memories. Yellow square predicts shock, and a second one, yellow square does not predict shock. And the problem is over time those two memories compete for expression. And this is one of the big challenges in treating anxiety disorders. We can get people in the clinic to not be so afraid of things, but now you get them out in a stressful situation and all of a sudden those fears come back. It's the fact that we have two memory representations that are competing that leads this to happen. - So what we found in our experiment is that the way to get around the problem of fear coming back is to remind the fear memory before we do extinction training. So to remind the fearful memory, we just present the yellow square again. This brings back the fear. Then we wait a little bit. And then we start with extinction training, which is presenting the yellow square again and again. This manipulation keeps the memory extinguished. It prevents the fear memory from returning. So the reason why it works is because we take advantage of a phase of memory called reconsolidation. And this is a process that happens naturally whenever we remember something. A nice way to think about it is like a file on your computer. You have a file that you-- a document you wrote and it's stored. Then you open it, you update. You put in new information. Then you save it and store it again. So now it's stored in a new form. It doesn't create a new file in addition to the old file. You have just one file, but now it's updated. So what we do is reactivate the memory. It goes into this phase called reconsolidation, which is basically the restorage of the memory. If we do extinction training at that time, it doesn't form a new memory. The information acquired through extinction is merged into the original memory and it changes its original properties. So now we have one memory but stored in a different form. - And now what we would expect is the case in that situation is when we wait a day, the fear doesn't come back. When we stress you, the fear doesn't come back. And that's exactly what we found. The big difference between this and what you see in the Eternal Sunshine of the Spotless Mind is here we're targeting a very specific fear memory, not your ability to recollect information. So in that movie Jim Carrey wanted to completely forget Kate Winslet altogether. Here, because this specific type of fear memory which is represented in your body's response to a fearful event, we're eliminating the memory of that. You will still be able to tell me what happened. And you will still have all of that information available, because that's another kind of memory we didn't target. - And that's a good thing, because if you supposedly erase memories, you don't want to create blanks in your life that the whole parts are missing. If you still remember the content, you have continuity in your life. You just change your emotional response so the intrusive emotional fear doesn't interrupt your everyday life whenever you remember. You can remember, but it's not stressful anymore. [MUSIC PLAYING] ELIZABETH PHELPS: So at this point how this works in the clinic is going to be all speculation. But what this data suggests might happen in the future is if you come into the clinic with a fear-related disorder, like a phobia or PTSD, if we can understand how these memories are restored when they're retrieved, much as we did in this study, we then may be able to time our therapeutic interventions in such a way where we aren't creating new learning that's overriding those earlier memories but actually rewriting them in a sense. If we can time that correctly so we can target these mechanisms, perhaps we'd have a more effective, long-lasting outcome. [MUSIC PLAYING]