Research studies on the cognitive effects of normal aging typically recruit older subjects who are well educated and who claim to be in good health. The rationale is that any cognitive impairments seen in such persons will reflect the effects of normal aging rather than poor education or disease. However, even such highly selected older persons often suffer from a variety of medical conditions that are major risk factors for neuropathology. One such type of neuropathology is evident on Magnetic Resonance Imaging (MRI) as areas of hyperintensity in the white matter of the brain. These WMH become increasingly common with advanced age and can be quite extensive without producing gross neurological symptoms. There is, however, evidence that WMH are associated with cognitive decrements. It is thus possible that some of the cognitive decline commonly attributed to """"""""normal"""""""" aging is instead the result of WMH. The study proposed here will examine whether WMH are associated with decrements in cognitive processes thought to be sensitive to normal aging. The study will recruit 150 older persons of the type commonly used in cognitive-aging studies; community-dwelling college-educated individuals 70-85 years old. Fifty college students will be recruited as a comparison group. The older subjects will receive an MRI that will be analyzed with a semi-automated quantitative segmentation software to determine the volume of WMH present. Both old and young subjects will be given tasks designed to examine three fundamental mechanisms currently theorized to underlie the cognitive decrements of aging; decreased working-memory capacity, cognitive slowing and decreased inhibition. The MRI and cognitive testing will be repeated two and a half years later in the older subjects to determine whether increases in WMH volume are associated with a further cognitive decline. This study will also examine the nature and severity of the cognitive decrements present in those older person who show no evidence of neuropathology on their MRIs. Thus, this project will both investigate whether WMH may be responsible for much of the cognitive decline typically attributed to normal aging and will examine the cognitive status of older persons with no MRI evidence of brain pathology.
