Take a moment, and remember, in as much detail as possible, a time in your life when you were REALLY SCARED!
If you tried, you could probably summon up a scary memory pretty easily. We are really good at remembering things that scare us. We have to be. If we face a threat once, and survive, it’s vital to remember the details so we can avoid that situation in the future, or survive it again if we have to. By studying how risks memories form, neuroscience is starting to figure out how to help us forget our fears. The implications for a wide range of psychological conditions is profound.
In experiments led by Jamie Peters of the University of Puerto Rico School of Medicine, rats were conditioned to fear the sound of a bell. Every time they heard the bell, they got a shock. Such fearful memories can then be counteracted with what’s called extinction training. You ring the bell but don't shock the rats. After a while, the animals learn that sometimes when the bell goes off, there’s no shock. Extinction training is a common therapy for people with a wide range of anxiety and fear-related problems. They are exposed in some way to the scary circumstance that created a fear memory, but without the harm that came along with it. It can work, but depending on the circumstances, extinction training can take a long time and repeated tries before it takes effect. Fear is protective, after all, so its stubborn.
Now for the magic. Knowing that a protein called Brain Derived Neurotrophic Factor (BDNF) is important for forming fear memories, and that an area in the brain just behind the forehead is involved in encoding these memories, Peters' team injected BDNF into that part of the rats’ brains, put the animals back in the cage where they had previously been shocked, rang the danger bell without shocking the rats, and after just one 'dose' of this extinction training, the animals were not as afraid as they had first been conditioned to be. It didn’t take several rings of the bell the way extinction training usually does. The BDNF injection and one ring of the bell were enough.
But extinction therapy has one important limitation. It doesn’t erase the old fearful memory. It just adds a new one. If you take fear-conditioned rats who have had extinction therapy and expose them to the the bell and zap them again, just once, they’re quickly back to the fearful state it took several such sessions to create in the first place. The old memory is still there, and easily revived. Wouldn’t it be great if we could totally erase the memory of what frightened us? That may be possible too, according to a remarkable piece of research led by NYU neuroscience post doctoral fellow Daniela Schiller. And this work was done on people!
Subjects were shown a colored square, and then got a shock. After just a couple of these sessions, they quickly learned to fear the sight of the square. They were brought back in a day later, and were shown the square again, and sensors on their skin revealed they were all afraid. They got no shock, a first round of extinction training, and were asked to wait around for a bit. Then they got a second round of extinction training, another glimpse of the scary square without a shock.
- One-third got this second extinction training ten minutes after the first.
- One-third got the same extinction training six hours after the first.
- The last third, as a control, got no extinction training at all.
Then they went home, and came back the next day. Just like the day before they were all shown the scary square. But this time, the people who the day before had their second extinction training ten minutes after the first one, FORGOT THE FEAR! It was GONE! They saw the square and nothing happened. The sensors on their skin looking for a fear response, didn't sense anything! The subjects who got the same extinction training six hours after the first one, and those who didn’t get extinction training at all, were still afraid just seeing the square.
Every time we recall a memory, we then re-encode it back into our memory, incorporating into the re-encoded memory any fresh information that goes along with it. Neuroscientists call this consolidation. This re-remembering is important. It lets us adapt to new circumstances. What Schiller and her team found was that there may be a window of opportunity for erasing fear if two sessions of extinction training happen between 10 minutes and 6 hours.
We don't know how that works, or just what BDNF is doing either. But we are getting closer to the day when a psychologist might be able to use a combination of drugs and therapy to honestly tell a patient suffering from debilitating fear to just “Fuhgedaboutit!”