While the earliest phase of Alzheimers disease (AD) pathology is often described as clinically silent prior workraises the possibility that early AD is associated with detectable alterations in autobiographical thought a classof cognition encompassing memories plans and other mental simulations related to our personal lives. Herewe introduce two multi-modal studies that investigate whether cognitive markers of early AD neuropathology canbe detected by deploying smartphone applications (apps) to track autobiographical thoughts in everyday life.Using two smartphone apps developed by our team to naturalistically assess cognition the proposed studieswill a) examine the sensitivity of real-world autobiographical thoughts to AD plasma and brain biomarkers inclinically normal older adults b) reveal the predictive and scalable potential of measuring autobiographicalthoughts in older adults for a host of longitudinal AD biomarker and associated health outcomes and c) shedlight on neurocognitive autobiographical thought characteristics that may separate normal from abnormalcognitive and brain aging. MPIs Dr. Grilli and Dr. Andrews-Hanna have formed a team of researchers withexpertise in smartphone-based assessment of cognition autobiographical thought functional magneticresonance imaging healthy and pathological aging and longitudinal analysis of large datasets. Leveraging ourteams interdisciplinary expertise we will execute an innovative two-pronged project harnessing in-lab at-homeand online assessment methods that will evaluate the relationships of AD biomarkers and aging to theautobiographical thoughts of 1225+ adults with a subset completing additional in-lab experimental cognitivetests neuroimaging plasma biomarker assays and longitudinal follow-up. In Aim 1 we will test the hypothesisthat among clinically normal older adults smartphone measures of autobiographical thoughts are sensitive toplasma AD biomarkers and resting state functional connectivity in the default network a brain network targetedby early AD. Aim 2 tests the hypothesis that these smartphone measures predict future plasma biomarkeraccumulation among older adults who were clinically normal at enrollment as well as future resting statefunctional connectivity of the default network and daily psychosocial / instrumental decline. Aim 3 deploys oneof our smartphone apps to a large remote clinically normal and genotyped cohort providing an opportunity toevaluate questions about effects of age and genetic risk for AD on autobiographical thoughts at anunprecedented scale. Across the aims we also examine how smartphone measures of autobiographicalthoughts compare to in-lab cognitive tests and if they improve sensitivity to aging and AD risk. To our knowledgethis project will be the first to use smartphones to track autobiographical thoughts as a means to identify cognitivecorrelates of AD biomarkers despite theoretical tenets and evidence that doing so could tap into the primarybrain pathway of AD. Ultimately our mobile tools may lead to more accessible cognitive tests of early ADincluding initial stages of amyloid and tau with broad impact for scientists clinicians and patients worldwide.