This week we learn about Alzheimer's disease, how it changes the brain and may be caused by the virus which causes cold sores. We probe your grey matter to find out how memory works, what goes wrong to give us false memories, and the science behind earworms - the songs that we can't get out of our heads! Also, GM plants that can survive a drought, why future chewing gum may contain magnolia bark and how a mirror can kill phantom limb pain. Plus, in Kitchen Science, we fool our senses with some plastic, some paper and a carpet!