Researchers from the Massachusetts Institute of Technology have found a special gene in mice. It could help people with painful memories forget bad experiences. It could help soldiers, crime victims and people who survived natural disasters. Many of these people have memories that make them very stressed. They have an illness called post-traumatic stress disorder (PTSD). Scientists hope to use their research to erase painful memories in humans. They want to replace stressful memories with positive thoughts and feelings. This would help millions of people with PTSD.

Scientists did tests to make mice forget their fear. They put the mice into a cage and gave them electric shocks. After many shocks, the mice were stressed and afraid of the cage. After the mice had "cage shock," the scientists put the mice in the cage again but with no electric shock. After some time, the mice no longer feared the cage. Their stress and fear changed to good feelings. The scientists looked at the brain activity of the mice. They were surprised to find the gene that replaced old memories with new ones. They will now try to find this gene in human brains.