Bringing an old memory back to mind would, you might think, strengthen it. But not so – when memories are recalled, they enter a surprisingly vulnerable state, when they can be reshaped or even rewritten. It takes a while for the memory to become strengthened anew, through a process called reconsolidation. Memories aren’t just written once, but every time we remember them.

This system allows us to rapidly update our memories with new information, for a more flexible and adaptable brain. It also means that the very act of remembering provides a valuable window of opportunity, during which memory can be manipulated. Now, a group of US scientists have done just that, exploiting this window to remove a simple fearful memory