Project Summary As Alzheimer's disease (AD) treatment strategies increasingly focus on prevention at the preclinical stage, a corresponding effort to improve detection of early changes in cognitive function is urgently needed. Subjective Cognitive Decline (SCD) provides a unique opportunity to identify emerging cognitive symptoms from the person's own perspective that can complement neuropsychological assessment at the preclinical stage. Furthermore, SCD has direct applications for AD prevention trials seeking to demonstrate treatment effects that impact study participants' daily lives. We propose to recruit a new cohort of SCD individuals who report a concern for recent, persistent changes in cognitive functioning. Individuals will be recruited from both the community and the memory disorders clinics (n=100) and will be followed over the course of 3 years. Specifically, we will capture high frequency SCD report (i.e., quarterly) that can be administered unsupervised via personal electronic device (e.g., computer, smart phone, tablet). In this way, participants will be able to complete assessments at-home, rather than coming to the clinic. SCD trajectories will be associated with other markers of disease severity, including in vivo AD biomarkers longitudinally, amyloid (Pittsburgh Compound B- PET) and tau (Flortaucipir-PET) and objective cognitive decline. The information gleaned from these complementary methods will improve our ability to identify high risk participants more likely to decline and to track clinically meaningful response to treatment.