Right now, in the brain cells of 12 million people around the world, there are messy, abnormal tangles of a protein called tau. Surrounding the neurons of these people (there are 1.6 million of them in Japan and 4 million in the United States) are plaques of a protein fragment called beta-amyloid.
In healthy brains, tau serves to both assemble and support the "scaffolding" systems that give neurons their structure and enable them to function. Somehow, the fragments of beta-amyloid cause tau filaments to change shape and tangle. The tangled fibers can't support their neurons, which die. Memories fade and are lost, and, eventually, dementia sets it. And as lifespans around the world increase, so will the number of people with neurodegenerative disorders.
Scientists have been trying to find a link between the tangles and the plaques ever since Alois Alzheimer described them in 1906 in the brain of a patient with dementia. And this week, for the first time, the link has been made.