Narrator:       This is Science Today. One of the hallmarks of Alzheimer's disease is the presence of a brain peptide called amyloid-beta. Researchers have been trying to determine to what extent is the presence of amyloid in the brain causative of the disease. Dr. Michael Weiner of the University of California, San Francisco says there has been some concern in the scientific community because there have been a number of clinical trials aimed at amyloid that have failed. 

Weiner:          And that's led some people to think, well maybe removing amyloid isn't going to give you a result, but there are other reasons. One possibility is that the drugs just didn't work very well. Another possibility is that if we waited until people are demented, it's too late.

Narrator:       Weiner is the principle investigator of a national effort called the Alzheimer's Disease Neuroimaging Initiative, or ADNI. The primary goal of ADNI is to identify early biomarkers of the disease and its progression for both the diagnosis and the development of new treatments for Alzheimer's disease. For Science Today, I'm Larissa Branin.