UNIVERSITY OF CHICAGO, THE
Normal aging can reduce memory resolution, or the degree of clarity and sensory detail in subjectively experienced recollections. However, we do not know the degree that these reductions are due to a primary loss of resolution abilities, diminished strategic or cognitively controlled processes, or both. The interaction of these factors at the behavioral level has limited understanding of aging effects on memory. Recent developments in fMRI research, along with well-characterized cognitive tasks, can lead to unique insights into the memory resolution problem. The recollection of previously studied pictures has been found to reliably activate specific object processing regions, reflecting the reactivation of high-level visual content in memory. Under appropriate task conditions this activity can serve as a neural signature for perceptually detailed recollections, providing a new way to test theories of memory resolution. The proposed research has two aims. Aim 1 is to understand how visually distinctive memories influence neural activity in aging. Recent research shows that aging can spare the recollection of pictures compared to words, owing to the enhanced perceptual distinctiveness and subsequent memory resolution of pictures. The degree that these distinctiveness effects influence control processes in aging is unclear. Experiment 1 tests the hypothesis that picture memories minimize the need to recruit prefrontally mediated control processes in both age groups, relying more on posterior object-processing regions that are less affected by aging. This hypothesis contrasts with a prevailing theory of aging and memory, which is that older adults recruit prefrontal control processes whenever they need to recollect specific information. Aim 2 is to investigate aging effects on memory resolution, independent from control processes. To this end, Experiment 2 uses a parametric manipulation of the resolution of presented pictures, and also manipulates the required level of cognitive control across groups. To avoid problems with direct comparisons of fMRI activity across age groups, these experiments will test for age x task interactions across comparable conditions and regions. These experiments will advance our understanding of aging effects on memory resolution and frontally mediated control processes, a topic with important health implications. Aside from control processes, memory resolution depends on the integrity of medial temporal and posterior cortical areas, regions that are most likely to be impaired in the preclinical stages of Alzheimer's disease. By characterizing normal age-related effects on memory resolution and control processes, this research will lay the foundation for future fMRI studies of memory resolution as a potential marker of the transition between healthy aging and age-related disease. PUBLIC HEALTH RELEVANCE: This project uses fMRI and cognitive tasks to investigate healthy aging effects on memory. Understanding how aging affects different memory processes is critical for developing fMRI tools to help diagnose healthy and diseased states, and for evaluating interventions that might help to improve quality of life.