The aim of the proposed research is to combine brain metabolic mapping and structural equation modeling, a statistical path analysis technique, to study postnatal maturation of the functional interactions of neural systems related to reinforcement, memory, and behavioral inhibition in the preweanling rat. In the proposed experiment, preweanling pups at 16-17 and 11-12 days of age will be trained, in a straight alley runway, on two reward schedules, patterned single alternation (PSA) and random partial reinforcement (PRF). Following training on these schedules, animals will be injected with fluorodeoexyglucose (FDG), a radio labeled glucose analog and then given 50 trials of extinction training, i.e. continuous non-reward. Immediately following training, they will be sacrificed and their brains processed for FDG. Glucose utilization in a number of brain regions will be quantified using image analysis sofware. Structural equation modeling will be applied to these data to quantify functional influences between anatomically connected brain regions. The network models derived from this process from PSA and PRF groups at each age will be compared. PSA and PRF comparisons in the 16-17 day old age group should reveal functional differences in the coordinated function of brain regions between animals demonstrating behavioral inhibition and perserveration, respectively. Comparison of 16-17 day old PSA and PRF groups to their 11-12 day old counterparts should reveal ontogenetic differences in brain activity related to the behavioral differences across the two ages. Handled controls will be included to control for brain activation related to handling and not learning per se. The major goal of this work is to contribute substantially to the understanding of metabolic maturation of brain regions related to reinforcement, memory, and behavioral inhibition, and how changes in their coordinated activity during postnatal development are reflected in behavior.
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