Brain Reward Circuits and Computational Modeling in Adolescent Anorexia Nervosa

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DESCRIPTION (provided by applicant): Anorexia nervosa (AN) is the third most common chronic illness among adolescents, and its mortality rate is 12 times higher than the death rate associated with all causes of death for females 15-24 years old. AN is characterized by severe weight loss and refusal to eat, suggesting altered brain processing of food rewards. In this application we will study in adolescents with AN brain reward pathways, and how those circuits are affected by malnutrition and re-feeding, as well as stress hormones that are frequently altered in AN. Our long term goal is to characterize pathologic brain circuits in AN that are biomarkers for the disorder, link those alterations to specific neurotransmitter mechanisms, and identify potential treatment targets for adolescent AN. In Aim 1. we test the hypothesis that adolescent AN is characterized by an increased response of dopamine related brain reward pathways. The proposed results will suggest that malnutrition in adolescent AN is associated with heightened brain reward sensitivity. In Aim 2. We test the hypothesis that weight recovered adolescent AN will have improved brain reward sensitivity compared to AN who did not restore weight, but will still show an exaggerated brain response compared to control adolescents. This will indicate long lasting alterations in brain reward function in adolescent AN beyond weight recovery. In Aim 3. We will test the hypothesis that the stress, feeding and reward related hormones cortisol, dehydroepiandrosterone (DHEA) and its sulfate (DHEA-S), will be associated with increased reward sensitivity in adolescent AN. This will indicate potential mechanisms that contribute to altered reward processing in adolescent AN. We will study adolescents with restricting type AN, ages 12-17 years old, when underweight at the begin of treatment, as well as after either successful weight restoration or failure to restore weight. Results will be compared to age and education matched healthy adolescents. We will use taste and monetary reward stimuli and tasks that are related to brain dopamine function, together with functional magnetic resonance brain imaging (fMRI). We will examine adolescent AN brain response to reward stimulus expectation, as well as unexpected and expected receipt of reward stimuli. Those brain processes have important implications on reward learning and conditioning. We will further apply on the brain imaging results computational models that simulate brain dopamine action, and this will help getting insight into dopamine related brain function in adolescent AN. Those models will also help identify the larger brain reward circuitry that involves the effects of cognition and emotion on brain reward function in adolescent AN and healthy controls. The stress hormones cortisol, DHEA and DHEA-S have implications on feeding and brain dopamine function and show alterations in AN. We will analyze those neurosteroid hormones in saliva and test their affect on brain reward function in adolescent AN.