PROJECT SUMMARY/ABSTRACT Patients with behavioral variant frontotemporal dementia (bvFTD) develop progressive and highly distressing symptoms of social and emotional dysfunction, including loss of empathy for other people. Scientific research has struggled to understand the specific causes of empathy loss in bvFTD because empathy is difficult to measure in a way that is meaningful and not biased by other factors, such as caregiver burden, and because individuals with bvFTD have highly variable patterns of cognitive and behavioral functioning. A relatively unexplored but promising avenue of scientific inquiry is the role of autonomic nervous system (ANS) activity in empathy loss in bvFTD. The ANS is comprised of two complementary subsystems, the sympathetic and parasympathetic nervous systems, which operate together to increase and decrease levels of physiologic arousal in response to cues from the environment. Patients with bvFTD show subtle abnormalities in ANS activity that are linked to symptoms of social dysfunction, including loss of empathy, but this line of research has been hindered by reliance on traditional methods of measuring ANS output, namely hard-wired EKG and skin conductance sensors, which restrict the movement of the patient and are sensitive to motion artifacts. Recent advances in wearable smartwatch technology allow for precise, unobtrusive measurement of ANS activity with built-in motion detectors to account for changes in ANS signals that are due to movement. Smartwatch technology is well-suited for continuous measurement of ANS functioning to detect subtle abnormalities that correspond to behavioral measures of empathy in bvFTD. This project has the potential to identify specific physiologic contributions to empathy loss in bvFTD, which can be used to develop new treatments and improve early detection of social and emotional dysfunction in bvFTD.