Adolescence: Natural Incentives, Motivation and Affect

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DESCRIPTION (provided by applicant): Human adolescents and their counterparts in a variety of animal models avidly seek out rewarding stimuli through heightened peer interactions, risk taking, and increases in food consumption and drug use. These behavioral features of adolescence are highly conserved across species, as are adolescence-associated transformations in forebrain regions (e.g., PFC, amygdala, accumbens, and associated DA input) implicated in these behaviors and in attributing hedonic value and incentive motivation to natural rewards, drugs of abuse, and their associated cues. A crucial core question remains, constraining understanding of problem behaviors in adolescence and attempts to discern their neural substrates: Are adolescent-associated increases in behaviors directed towards natural rewards and drugs of abuse related to increases or decreases in the value they attribute to these rewarding stimuli? On the one hand, adolescents might pursue certain natural rewards and drugs because they normally exhibit (or are prone to develop) strong incentive motivation for these stimuli. Alternatively, adolescents may avidly seek these rewards because they are attempting to compensate for an age-related insensitivity in reward circuits that produces a partial, developmentally expressed anhedonia. Using an established model of adolescence in the rat and focusing on three natural rewards of particular significance for adolescents: social interactions, novelty, and appetitive taste) stimuli, the proposed work will test these possibilities and determine age-specific expression of neural markers for these rewards. Work in this proposal will answer the following questions: Do adolescents exhibit attenuated hedonic affect to natural rewards relative to mature animals (Sp. Aim 1)? Do they express increased incentive motivation for natural rewards (Sp. Aim 2) or are they unusually prone to develop incentive sensitization to these rewards following chronic drugs or stressors (Sp. Aim 3)? Do adolescents exhibit unique patterns of regional brain activation in PFC, amygdala, accumbens and related circuitry in response to natural rewards and their cues when compared with mature animals (Sp. Aim 4)? The proposed work will further understanding of why adolescents behave the way they do, identify candidate neural regions underlying these age-related proclivities, and help inform strategies for the treatment of adolescents exhibiting drug abuse problems or other excessive reward-directed behaviors.