Alzheimer’s patients in the early stages of the disease do not lose memories. They are stored. Their problem is accessing them a few hours later. A team of MIT neuroscientists has made this discovery of revolutionary implications, for all its simplicity. Their experiment with mice suggests that the short-term memory is not being lost forever. Alzheimer’s patients simply lack the capacity to retrieve them a little while later. In a lab experiment, mice with unaltered memories and those engineered to develop Alzheimer’s syndrome were enclosed in a chamber where they were exposed to shock in their feet. Both groups of mice recalled the painful experience a few hours later when brought to the same place. A week later, however, the healthy ones still reacted in fear when placed in the same chamber, whereas the animals with Alzheimer’s appeared to have forgotten about it. In recent years, researchers led by Susumu Tonegawa have identified cells in the brain’s hippocampus that store specific memories. “The researchers have also shown that they can manipulate these memory traces, or engrams, to plant false memories, activate existing memories, or alter a memory’s emotional associations,” says a post on the MIT website. By action or omission, memories help shape our identity and life. Alzheimer’s is perhaps one of those diseases that are more painful for families and friends than the patients themselves. As the condition sweeps away all the traces of past and present, they see the person they remember becoming someone else, a blank memory of a life gone before the body has. The possibilities opening up for Alzheimer’s patients can be nothing but auspicious. Tonegawa’s research may provide them with a tool to access their memories, locked away beyond their reach. The remedy may be like a ladder to reach a book on a high shelf. Yet as so many advances in sciences, memory engineering creates disturbing scenarios as well. There are times in which all of us would like to erase painful memories—of love unrequited, of frustrations, traumatic moments. There may be a case to be made for that. What of persons who have seen violence of the worst kind? “The world forgetting, by the world forgot. Eternal sunshine of the spotless mind!” in the words of Alexander Pope, which inspired a 2004 movie that explored the theme of selective memory. What would become of a world in which painful memories were erased? Would it be happier, and wiser? Probably neither.