Unraveling Alzheimer's

As much as has been learned in the past few years about how Alzheimer's progresses, a lot more study needs to be done. The latest research could wind up proving that plaques and tangles are not causes of death, but more like tombstones--they tell you where people are buried but are not responsible for killing them. Or it could be that the only way to prevent Alzheimer's is to stop the plaques from forming decades before any symptoms appear.

Even if scientists figure out precisely how Alzheimer's destroys brains, it is not clear that they will be able to stop it. But it's also clear that no one will be able to treat the disease--let alone cure it--until they do.

--With reporting by Alice Park/Boston