Project Abstract: A neurocomputational model of age-related differences in navigation For many individuals, navigation skills decline with increasing age, particularly for novel environments with which the individual is not already highly familiar. Impairments in navigation are particularly evident for those with mild cognitive impairment, a significant risk factor for Alzheimer’s disease and Alzheimer’s related dementia (ADRD). Yet, our understanding of age-related differences in navigation remains underdeveloped. The dominant explanation for age-related differences in navigation relates to impairments in the cognitive map, yet the explanatory capabilities of this model are limited, particularly in explaining the heterogeneity of age-related differences in navigation. Here, we seek to develop a novel computational model that employs an approximate Bayesian framework to better account for age-related differences in navigation. We focus in particular on testing hypotheses related to greater reliance on multimodal cue integration (Aim 1) and strategy rigidity (Aim 2) in older adults. These ideas will be tested using highly immersive virtual reality in which participants don a head-mounted display and free ambulate hallways. The experiment in Aim 1 will provide critical tests of our computational model by employing conditions involving both matching and mismatching visual and idiothetic (body-based) cues. This will allow us to test Aim 1 and whether older adults rely on multimodal integration to a greater extent than younger adults. The experiment in Aim 2 will test whether older adults rely on previous trials to a greater extent than younger adults, particularly for matching and mismatching trials. This will allow us to test the extent to which older adults might show strategy rigidity by over- relying on past trials. Aim 1&2 will also allow us to test ideas related to individual differences in navigation strategies, which can be assessed based on the variability in subject responses within the different conditions tested. Finally, we will test a subset of individuals with mild cognitive impairment (MCI) to provide initial and exploratory testing of their navigational deficits in our experiments. The outcomes of this project have the potential to provide a new understanding of age-related differences in navigation by developing a sophisticated and novel computational model that we test in detail with experiments in immersive virtual reality.