When was the last time you and a friend or spouse argued over memories of a shared event and you swear your version is the right one? Our memories are not just unreliable; in the future they could be manipulated.

We know from studies in the 1940s that memories are stored in the temporal lobe and the hippocampus. It's our experiences that produce changes in neuronal chemicals and connections which create memories which are stored. Scientists have now identified the precise cells in a neural network involved in this process.

They did this by creating mice that were genetically engineered to express a light sensitive protein in neural cells of the hippocampus which is where we store spatial memories.

The mice were first placed in box A, and as they began storing memories of the box, it activated the spatial neurons and thus the engineered light sensitive proteins. So when the mice were then placed in box B where a mild electrical shock was applied to their feet as flashes of light pulsed, their memories of box A were activated. Remarkably, when the mice were placed back in box A, they showed fear even though they had received no shock therapy there. The light had changed their memory of that box.

This means the scientists had implanted a false memory. Wow, shades of the X Files! Imagine people being programmed or having their memories altered. Think of war vets or victims of violent crime who could be cured of post traumatic stress disorder.

But is that wise? We, along with other scientists and ethicists, will grapple with these dilemmas as this technology develops in the future.