For years, he was known only as H.M. to protect his identity. But when he died last Tuesday, we learned his name was Henry Gustav Molaison.
After a bike accident when he was only nine years old, he started having uncontrollable siezures. And when a surgeon tried to help by performing a brain operation, the unimaginable happened.
While leaving him fully functional, the surgery left him incapable of remembering anything for more than 20 seconds. For example, every time he saw his doctor, he thought he was meeting him anew.