PROJECT SUMMARY The long-term career goal of the K99/R00 applicant, Dr. Stephanie Balters, is to continue her career transition from engineering and functional Near-Infrared Spectroscopy (fNIRS) neuroimaging into the clinical neuroscience of Posttraumatic Stress Disorder (PTSD). Specifically, her aim is to develop fNIRS neuroimaging methods that will advance the science of PTSD in addressing questions about brain mechanisms underlying this complex disorder, with the goal of improving diagnosis and treatment of PTSD (i.e., Precision Medicine). Through her Ph.D. and postdoctoral training, Dr. Balters has acquired fundamental knowledge in the psychophysiology and neuroscience of acute and chronic stress; she has advanced the measurement with various psychophysiological sensors from the laboratory into naturalistic environments (e.g., salivary cortisol, heart rate variability, skin conductance); she has built novel unobtrusive stress sensors (e.g., steering wheel stress sensor) and subtle interventions (e.g., Precision Health breathing intervention); has gathered considerable experience in applying fNIRS neuroimaging within naturalistic environments; and has analyzed existing fNIRS-PTSD datasets. However, she has not yet conducted an fNIRS study focused on a clinical PTSD population. To facilitate her career transition to a research faculty position and conduct reliable and safe PTSD neuroimaging research independently (yet in close collaboration with her licensed clinical colleagues), she further requires essential research skills and career preparation. Specifically, Dr. Balters will acquire training in 1) the clinical presentation and diagnosis of PTSD; 2) concurrent fNIRS-fMRI; 3) machine learning algorithms, with focus on Gaussian Models; and 4) skills for independence. Her short-term goal is to acquire the critical didactic and “hands-on” training (1-4) during the K99 period, and to apply these new skills in the R00 period independently. The overarching objective of the proposed K99/R00 research is to develop novel brain imaging methods that enable the assessment of PTSD brain biomarkers in an affordable, portable, and repeated manner. The central hypothesis is that aberrant brain function related to PTSD can be measured with fNIRS. Three specific aims will be addressed: (1) derive cortical biomarkers of PTSD with fNIRS; (2) infer deep brain biomarkers of PTSD with fNIRS; and (3) assess day-to-day fluctuations of fNIRS biomarkers. Successful completion of this K99/R00 research will make significant inroads to providing scientists access to affordable and valid biomarkers of PTSD for diagnosis and improved understanding of brain mechanisms underlying PTSD. Dr. Balters will be equipped with a unique and interdisciplinary skill set to advance PTSD neuroimaging with fNIRS. To bolster her potential for success, Dr. Balters positioned herself within an outstanding research and academic environment at Stanford University, secured the support of except...