This application investigates visual sensory processing in Alzheimer disease (AD), amnestic mild cognitive impairment (aMCI), and normal aging. Few studies have evaluated potential cognitive predictive measures for AD in high-risk subjects with aMCI. This study addresses this shortcoming by examining our hypothesis that the sensory processes that allow visual motion processing to enhance visual recognition of 3D objects are impaired in persons with AD and a subset of persons with aMCI compared to healthy, age-matched controls, and this impairment is independent of visual memory function. In studies with young normals (YN), recognition of 3D objects viewed in positions rotated >45 degrees from canonical views is difficult or impossible unless views are linked by rotating motion. Thus, motion plays a role in 3D object recognition. It is unknown how normal and pathological aging affect motion enhancement of 3D recognition. Enhancement relies upon dynamic interactions between functionally specialized regions of the visual association areas in the parietal and temporal cortex via corticocortical connections. Since neurons that furnish these connections are selectively vulnerable to degeneration in AD, impaired motion-enhanced 3D recognition skills might distinguish normal aging from prodromal AD. The rationale for our hypothesis is further supported by recent evidence of impaired optic flow, or visual motion processing, in a subset of patients with aMCI. In order to simulate life-like 3D images, we developed a protocol using a novel virtual reality technique to measure motion-enhanced 3D recognition skills. Our preliminary data with YN reveal that our IVE protocol detects the expected enhancement. In this study, we propose to use our IVE protocol to measure motion-enhanced 3D object recognition skills in patients with AD, aMCI, and healthy age-matched controls and correlate results to visual memory function. Our long-term objective is to examine visual sensory processing interactions between specialized regions of the cortex using behavioral methods and functional imaging with longitudinal studies of aging and aMCI. Results from this study will provide a foundation for future studies to develop a visual sensory measure that distinguishes normal aging from the AD prodromal phase, which is crucial for development of drugs that prevent or slow the onset of AD.
