Question: Would it be possible to change someone's memory?

Martha Havenith answered on 22 Jun 2015:

Hey Sir Anton, good question! Scientists have just managed to do a version of that in mice this year! It’s a really amazing new finding, especially because it was easier to do than lots of people thought. We have known for a while now that memories are formed and remembered through activity in a part of the brain called the hippocampus (it’s in the middle of the brain and looks like a sea horse, that’s where the latin name comes from). But until now no one had managed to change hippocampus activity and show that it changes memories.

In this new study, what they did was that they put a mouse in one specific room (say the red triangle room) and gave it a good/bad experience there (either some nice food or a small electric shock). Then they genetically changed all the hippocampus neurons that were active when the mouse was in the red triangle room, so that they could activate all those neurons with light whenever they wanted (if you like I can give you details on this step, but for now it doesn’t matter how exactly this works). Then they put the mouse in a totally new room (say the blue circle room) that it had never been in before, and at the same time they activated the neurons from the red room. Normally mice wouldn’t really care about a new room, probably explore it a bit; but those mice either showed signs of fear or happiness in the new room, depending on what they had experienced in the red triangle room. So basically the memory from the red triangle room got ‘transplanted’ to the blue circle room.
Obviously these are really basic memories (‘I felt good/bad in this room’) – we would probably have to do a lot more precise things than just activate a whole lot of neurons to make a mouse remember that one time it found a peanut in the corner of the cage and fought for it with its brother…. And also, we definitely wouldn’t know yet how exactly to use the same technique in humans. But people have already said that this might be a great way to help people with awful memories (e.g. from wars) that are making them suffer. This technique could change/erase such memories, or at least decrease their power over the person’s emotions.