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Many of the tests involve neural adaptation, in which Johnson is shown images in quick succession. In normal people, the brain grows familiar with the images, reacting less strongly to pictures that are repeated. That shows up as reduced activity in the visual cortex. In Johnson's case, the scientists expected that without a working hippocampus, learning of this kind would not happen if the repetitions occurred after a significant delay. But confounding expectations, it did, which means she is learning some other way. "That's a riddle we have to solve," says Kastner.
Ultimately, neuroscientists hope their memory research will lead to treatments for people with dementia or traumatic brain injury. At Toronto's Baycrest research hospital, for example, neuropsychologist Eva Svoboda is part of a team that uses smartphones and other technology to create a sort of artificial memory.
The program, known as Memory Link, takes advantage of the fact that many people with amnesia still have an intact procedural-memory system so they can learn the gestures and icons that let them navigate through a phone. "It's a huge, huge leap for patients," says Svoboda. "They can store virtually unlimited information, take pictures, write memos, set alerts to go off for medications or appointments."
As a result, studies by Svoboda and her colleagues have shown, many patients go from being utterly dependent on families and caretakers to taking some control of their own lives. "In some cases," she says, "spouses have been able to return to work, and patients have avoided moving into nursing homes." The advent of wearable technologies could bring even greater benefits, says Svoboda. A device called SenseCam, for example, developed by Microsoft Research and worn on a strap around the neck, takes photos automatically throughout the day. "Your spouse comes home and asks, 'What did you do today?'" says Svoboda, "and this camera has captured that."
Face-recognition software on a device like Google Glass could be even more useful. "Most of our patients," says Svoboda, "are unable to recognize people they've met since their injury." She imagines a scenario in which Glass figures out who someone is, searches Facebook and the patient's calendar and discreetly supplies all the information the patient needs to avoid an awkward situation. Using a smartphone or some other technology is not the same as restoring a person's memory, of course; it's comparable to providing glasses to someone who's nearsighted. Restoring memory function is more like LASIK--a true repair--but for the brain, that is years away, if it's even possible.
What's not possible is answering the inevitable question of what Johnson's life feels like. What sort of awareness does she have? "She's obviously aware of her own existence," says Kastner. "She's conscious. But we do not know exactly what that self-perception is. That would be a very interesting question to get at if one could."