|Comment by Randy L. Buckner and Cindy Lustig
A major challenge to developing therapies for Alzheimer's disease is the availability of valid and robust diagnostic markers. Clinical assessment and cognitive testing have traditionally been the gold standard. Over the past decade, there has been an increasing emphasis on two categories of neuroimaging markers—those based on structural measures, and those based on metabolic measures. Greicius and colleagues, in their recent paper in the Proceedings of the National Academy of Sciences (2004), suggest a novel diagnostic marker for Alzheimer's disease, based on functional MRI measures.
Their work is based on the recent discovery of a "default network" that is ubiquitously observed in brain imaging studies of healthy, young participants (Raichle et al., 2001). Default network activity is observed during periods of rest and passive tasks that do not require targeted, effortful processing. Anticipating the work of Greicius and colleagues, it is...