Introduction

Aging is a complex process both dreaded and honored, celebrated for its achievements and mourned for its deficits. The quest of ages has been to understand aging with the hope of forestalling, reversing or even abolishing this process. Contemporary scientific investigations into aging can be seen as further endeavors along this path. There has been much focus in contemporary science on the brain as the locus of key aspects of the aging process; the wisdom, insight, clarity of the old as well as the forgetfulness, dulling and slowing of senescence.

Neuroimaging is a powerful tool for the exploration of the brain and has in many ways supplanted the neuropathological investigation of autopsy-derived specimens as the gold standard for the study of the brain. Autopsy studies have always been limited by the difficulties in gathering large numbers of brains, a selection bias usually involving previously ill subjects and artifacts related to agonal events as well as the fixation of the brain. Neuroimaging allows the study of large populations in vivo. As well, subjects can be studied repeatedly, allowing for prospective studies. However, the newness of these technologies remains evident in the ambiguities that surround interpretation of many so-called abnormalities. There is no fully comprehensive or standardized normative baseline across the age spectrum for comparative interpretation of any neuroimagingderived data. Questions abound about neuroimaging findings and what they represent in terms of neuropathology and certainly in terms of brain function.