A Neuroeconomic Study of Choice Consistency in Aging

The attribution of value to prospects is a fundamental element of decision-making, as most day-to-day decisions involve comparing items. Studies on aging document behaviors reflecting difficulties in making comparisons between options, in particular when those options are complex. Given the growing complexity of economic products (insurance, savings, mortgages or even telephone plans), older adults may have difficulty making decisions that accurately reflect their underlying preferences. It is plausible that this difficulty is linked to age-related brain function decline within sectors of the lateral prefrontal cortex implicated in working memory and cognitive control. This study assesses age-related changes in how the brain computes value and makes value comparisons using a well-established economic paradigm, the "generalized axiom of revealed preference" (GARP) Task, that tests the internal consistency of a subject's preferences by offering repeated choices between bundles of goods. A preliminary study suggests that aging is associated with greater GARP-Task inconsistency. Although the neural correlates of GARP inconsistency have not been directly established, indirect evidence suggests that the medial orbitofrontal cortex is important in all value-based decision-making, and that areas in the lateral prefrontal and parietal cortices (fronto-parietal network) are important for maintaining consistency in complex decisions (e.g., multi-attribute decisions). Aging is associated with structural and functional deficits within the fronto-parietal network. Therefore, the investigators believe that studying the neural correlates of the GARP-Task is a promising approach to investigate decision-making deficits in aging. The investigators will recruit 45 young adults, and 45 old adults. Participants will complete the GARP-Task and an functional Magnetic resonance imaging (fMRI) variant designed to isolate neural correlates of valuation of single items, of multiple instances of the same item ("scaling") and of sets of distinct items ("bundles"). Brain activity will be related to diagnosis and to variance in GARP-Task inconsistency. Given the prominence of age-related decline in working memory, the investigators hypothesize that age will be associated with higher GARP-Task inconsistency and to deficits in conditions that require manipulation of value signals (scaling and bundles). The investigators anticipate that these deficits will be associated with low recruitment within the fronto-parietal network and with reduced functional connectivity between this network and the medial Orbitofrontal Cortex (OFC).