PROJECT ABSTRACT Sensory over-responsivity (SOR), or strong negative reactions to and avoidance of innocuous sensory stimuli, affects about one in five school-age children and about two-thirds of children with autism spectrum disorder (ASD) and several other common neurodevelopmental disorders. Children with SOR experience considerable short- and long-term distress and impairment including fear and anxiety, poor sleep and nutrition, isolating social difficulties, and increased risk of mental illness. The cost of SOR in childhood is compounded by its disruption of developmentally appropriate social and situational experiences and its deleterious effects on family functioning. Despite its prevalence and impact on health and wellbeing, the causes of SOR are poorly understood and existing treatment approaches have met with limited success. Identifying the specific neural mechanisms that are disrupted in SOR could provide insights into its etiology and suggest promising approaches for developing effective interventions. Studies of typical sensory processing have revealed basic neural mechanisms that promote adaptive sensory responses, highlighting a powerful new translational approach to investigating the neural bases of SOR. The goal of this K99/R00 Pathway to Independence Award is to provide the applicant with the training needed to test if these neural mechanisms are disrupted in children with SOR and to support her continued success as an independent investigator. To achieve this goal, the applicant has assembled a committee of exceptional mentors and experts who will provide her with training in clinical presentations and assessments of ASD and SOR (Drs. Constantino, Sylvester, Green, and Pruett), administering functional MRI scans to children with and without ASD and SOR (Drs. Green, Sylvester, Dapretto, Pruett, and Dosenbach), applying multilevel models to complex datasets (Dr. Jackson), and developing skills for success as an independent investigator at a major research institution (all committee members). The proposed training will allow the applicant to test predictions about the relationship between one neural mechanism (suppression) and SOR in children using existing data and to pilot a functional MRI task to assess a second neural mechanism (surprise) in children during the K99 phase. Results from this work will inform the R00 phase, which will entail testing whether three neural mechanisms (adaptation, suppression, and surprise) are attenuated in sensory and fronto-limbic brain areas of children with SOR, both with and without ASD. This innovative research approach will clarify whether predictive mechanisms are disrupted in children with SOR and localize disruptions to specific brain areas, advancing scientific understanding of SOR and highlighting promising targets for interventions to be tested in a R01. Collectively, the proposed training and research will provide the applicant with the data, tools, and skills needed to launch a succe...