Project Summary/Abstract. It is now understood that cerebrovascular dysfunction contributes to a host of neurocognitive disorders including the reduction in cognitive capacity with typical aging as well as the more serious impairments resulting from vascular disease and dementia. Cerebrovascular pathology is also highly prevalent in patients with Alzheimer’s disease (AD) and is an important factor contributing to the conversion from an independent state of mild cognitive impairment to the functional dependence associated with Alzheimer’s dementia. Thus, vascular health and disease are important mechanisms contributing to heterogeneity in cognitive aging and progression to vascular and Alzheimer’s dementias. Unlike the proteinopathies of AD and other neurodegenerative conditions, vascular health is immediately modifiable through behavioral and lifestyle factors, as well as a range of pharmacological and device related interventions. Thus, it is critical to develop methods for quantitative tracking of metrics of cerebrovascular health that could be used to detect the earliest stages of abnormalities that may require intervention. Optimally, such technology would be wireless, mobile/web interfacing and would be very low cost allowing for accessibility to traditionally medically underserved populations. We have designed and prototyped such a device that would permit widespread cerebrovascular monitoring in older adults. The goal of this R21 proposal is to complete the development of, and to validate this novel low-cost cerebral oximeter that can be used to screen for cerebrovascular disorders that contribute to cognitive impairment and increase risk for the development of AD. To do so, we will aim to Specific Aim 1: 1a) complete the design and casing and programming of our existing developed device; 1b) to optimize the design for high performance and reliable physiological signal detection; Aim 2: 2a) to validate performance of the low-cost mobile oximeter relative to gold standard high grade cerebral oximeter; 2b) to validate performance of the low-cost mobile oximeter relative to cerebral physiology measurements obtained by magnetic resonance imaging. The proposed sensor would promote widespread cerebrovascular monitoring in individuals at risk for vascular dysfunction and neurocognitive disorders. Ultimately, in the future, we aim for this sensor to be translated for use in clinical practice for generalized primary care as well as specialty clinical use.