Science thomsonreuters.com

Half of the story on how the brain processes memories is that when you acquire a new memory it's not stored in the brain immediately, but takes a few hours to get stored.

This is known as consolidation; the transformation of our memories from an unstable to a stable state. This has been the accepted thinking for years: that once a memory is wired into your brain, it is consolidated and it stays that way.

In 2000, I tested the basic idea of what happens when you recall a memory that has already been stored in your brain.  What we found was that when you remember something, it 'came off the hard drive', so to speak.  It became unwired, un-stored, and had to be restored, and if you block one of the molecules that are important to the storage process for consolidations, then we got a memory loss the next day, which is crazy because according to 150 years of studies, once a memory is stored in your brain, it stays that way. And so it suggests that when you recall a memory, it becomes un-stored and restored.  The basic implication of this is that the consolidation theory is wrong.

And so this re-stabilisation idea is now called re-consolidation. It has been shown not only in responses to pain and fear, but also for neutral and happy memories.

One of the defining features of this kind of memory is that you can also enhance the memories during this de-consolidated time frame. The immediate clinical implications are huge. Take somebody with post-traumatic stress disorder (PTSD). Say they've been in a war, or a victim of rape.  They can't move forward in time, they're stuck psychologically because of what's happened to them. Because of their memories.

A lot of the time a memory comes back and they continue to relive the trauma and it's really intense. One school of thought was that the trauma is so extreme the memory gets stored and becomes hyper-strong.  It's like a flurry in the emotional system: once it starts, the rest of the brain has a hard time stopping it. So the rest of the brain can try to stop the emotional system but, like bicycle brakes on a Ferrari, it's a tough thing to do. You have to catch it before the clutch goes. The emotional memory just becomes so crazy and so robust that normal brain mechanisms are simply overwritten.

One of the things that can enhance the memory process is something called the beta-adrenergic receptors. So we can remember emotional things better than we can recall the usual, mundane things. If I asked you what you did on your 16th birthday you could tell me a whole bunch of stuff, but if I asked you what you did a couple of Thursdays ago, when nothing important was happening, you probably wouldn't be able to.

What happens with emotional events is that the memories cause stress hormones to be released, and one of which is adrenalin. And by action on the amygdala on the beta-adrenergic receptors, they can make memories stronger. Roger Pitman had an idea that maybe what happens with PTSD is that the trauma is so strong and so much adrenalin needs to be released that it becomes super strong.

He tested this idea by giving a pill that blocks these receptors to ER patients who had just had trauma. And the people who had the pill had a low probability of developing PTSD. So it's very consistent with the idea that these memories are too strong. But then the problem is for effective general treatment, the consolidation time window is closed within four or five hours. But most people won't go to a clinic for PTSD treatment immediately or even up to a year after the event, by which time it's too late.

With reconsolidation though, we could create a time window during which physicians could intervene.  So now when somebody has PTSD and they go through the doctor, the doctor says 'tell me about your trauma' and if these memories do undergo reconsolidation, then they should revert to an unstable stage. This will allow a course of treatment that blocks the fear part of the memory from being restored. And so when you ask these patients the next day, they would recall the events but not the emotional memory. The part of the brain that causes the stress is blocked off.