PROJECT SUMMARY The proposed research will use behavioral, neuroimaging, and naturalistic approaches to understand the neurobiological mechanisms underlying daily life activity participation in older adults and its relationship to cognition and emotional experience. There is a strong foundation of research demonstrating reliable age- related decreases in many aspects of cognitive ability that are coupled with changes in the locus coeruleus- norepinephrine system, with the locus coeruleus identified as one the earliest sites of Alzheimer’s disease pathology. In parallel, engagement in a wide variety of activities and experiences in daily life has been associated with the maintenance of cognitive function, emotional well-being, and brain structure and function. Although there have been theoretical developments linking cognition, locus coeruleus-norepinephrine system function, and exposure to environments enriched with variety and novelty, with resilience to Alzheimer’s disease pathology, there have been no studies that have rigorously tested this construct in humans. The current proposal provides a novel perspective on this issue, by employing a multilevel, multi-modal framework to study the behavioral and neurobiological mechanisms underlying age-related shifts in activity participation, and to directly link these changes with in vivo measurements of the locus coeruleus-norepinephrine system and Alzheimer’s disease pathology. The project directly tests the hypothesis that varied and diverse activity participation in daily life contexts is associated with cognition and emotional experience by using the combination of ecological momentary assessment (EMA) and novel passive sensing approaches involving repeated sampling of daily life activities, experiences, and locations/contexts across the adult life span. Further, these rich naturalistic observations of daily life activities are coupled with ultra-high-resolution imaging measures of locus coeruleus structural integrity to test for the relationship between the integrity of the locus coeruleus-norepinephrine system and daily life activities and experiences in older adults. Finally, the project will feature the first-ever assessment of the relationship between in vivo markers of Alzheimer’s disease pathology and daily life activity participation in older adults, using state-of-the-art tau PET and intensively sampled daily life activity participation assessed with both EMA and cutting-edge passive sensing methods. A key component of the project is its exploration of mobile technologies as a means to monitor older adult activity participation during daily life, and their potential utility as a tool to enhance cognitive and brain health. As such, the proposed work represents an essential first step in developing both behavioral and biological targets for motivational interventions that promote the maintenance of cognitive health and resilience to pathology in older adulthood.