ABSTRACT
The refinement of in vivo imaging approaches to investigating the structure and function of the aging brain has provided the opportunity to strengthen our knowledge of the biological substrate of normal aging and late life neurological and psychiatric disorders. While postmortem studies are biased toward the end stages of disease, functional and structural imaging have permitted us to characterize the brain changes accompanying early Alzheimer s disease (AD). As more effective therapeutic approaches to slowing (and potentially reversing) disease progression are developed, the role of imaging in determining pre AD or high risk conditions becomes increasingly important. The goal of applying non invasive means to identify the transition state of mild cognitive impairment (MCI) is of considerable public health importance. Further, emerging imaging strategies may be used to monitor the efficacy of therapeutic regimens.