Wipe out: Can you remove memories?

In this extract from episode six of Breaking Science, Doctor Chris Smith and Helen Scales discuss a scientific development which might, one day, lead to the ability to 'zap' memories

Helen Scales: Have you seen a film called The Eternal Sunshine of the Spotless Mind? I quite enjoyed it, actually.

Chris Smith: I haven't. Who’s in it?

Helen Scales: Jim Carey and Kate Winslet, and what happens is she wants to have the memories of an ex-boyfriend taken out of her brain. But,  this kind of fantastical idea might not be confined to the realm of make-believe, because one day this could be a human reality. A team of scientists, led by Joe Tsien from the Brain & Behaviour Discovery Institute at the Medical College of Georgia in the States, have developed a way of rapidly and specifically erasing memories from mice.

The study is in this week’s edition of the journal Neuron, and it revolves around an enzyme called calcium/calmodulin-dependent protein kinase II. A big mouthful but otherwise known as CaMKII, and this has been linked to many different aspects of learning and memory. And they used mice that have actually been genetically modified to have an over-expression of this CaMKII gene, but they also were able to turn it on and off for specific lengths of time, by injecting a specific inhibitor molecule into the brains of these mice.

Chris Smith: So what exactly did they do in this study, and how did they prove that they were able to erase these memories?

Helen Scales: They took these mice, and they did various different things to them, but one of the main things was they gave them a shock. They put them in containers and put a really loud noise in them, and then later on you can look and see if that mouse has actually remembered that shock and that fear by something called the freezing response. You can put them back in the same container, and if they stop and don’t move, except for breathing, then that gives you the idea that they’ve actually remembered that shock from before.

Chris Smith: And they’re frozen because they’re anticipating it might be going to happen again?

Helen Scales: Exactly, and so what the scientists did was having exposed these mice previously to that fear, to that shock, they put them back into the container, up to a month later, and then they turned this gene back on again so that what they think actually is linked to the erasure of that memory. It turned out, by doing that, the mice didn’t actually freeze so much. They didn’t freeze, they didn’t remember that fear memory from before.

Crucially, it was at the point of recall that they were doing this, switching on and off of the gene, and by doing that, it only affected that specific memory that they were trying to remember. They were in that box thinking 'you know, I know this, I’ve been here before and I’ve been shocked before, something about this I remember', but by putting the gene on at that exact point, that’s the only memory that’s affected. It leaves all the other ones alone.

Chris Smith: And you can see why that would be really helpful, because there are lots of human conditions like post traumatic stress disorder where people remember certain memories too well and they experience all the stress that goes with it. So if you could selectively abolish a memory, in that way, that could be therapeutically very useful?

Helen Scales: It is the exactly sort of thing they’re looking to apply this to, but Tsien and his colleagues are really eager to point out this is very early stage and you won't be seeing memory-wiping pills on pharmacy shelves any time soon.

Chris Smith: Well hopefully people won't erase their memory of what you’ve just told them - fingers crossed.

Listen to the full episode of Breaking Science - originally broadcast October 2008