When you first meet Lonni Sue Johnson, it takes a few moments to realize that something isn't quite right. Leave the room for a moment and come back, however, and things become clear. "Hello!" she says brightly, as though she's never seen you before. "Would you like to see my drawings?" And if you leave again and return once more, she'll greet you the same way. Because as far as she knows, she never has seen you before.
Johnson, who was a hugely successful commercial artist and accomplished amateur violist, is profoundly amnesiac. She's essentially unable to form new memories: some experiences are gone in seconds, others in minutes, but next to nothing endures. She can't bring up many old memories either.
Such cases of annihilated memory are very rare. Some are caused by traumatic brain injury; others, like Johnson's, are the result of viral encephalitis, which often kills its victims or leaves them comatose. But they're also extraordinarily valuable: by looking at how illness or injury robs people of memory, neuroscientists have an opportunity to gain insights into how it works when all is well.