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Laura Padilla, Ph.D., Winner of the 2018 NIMH Three-Minute Talks Competition

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Severe neuropsychiatric illnesses involve drastic changes in experiencing rewards from increased risk-taking behaviors, like gambling and addiction, to a lack of finding things enjoyable. Many of these same illnesses, including substance abuse, depression, and schizophrenia emerge during or soon after puberty, which itself is considered a time of increased risk taking and reward seeking even in healthy adolescence. However, little is known about how the process of puberty may affect the brain's circuits involved in reward processing. The nucleus accumbens, shown here, is a key reward processing region in the brain. It has been shown that in adolescence this region is more sensitive to rewards compared to both children and adults. Although, most studies focus on age and do not define puberty per say. The hormonal events that make up the puberty transition may specifically alter nucleus accumbens sensitivity to reward and could contribute to the observed increase in adolescent risk-taking behavior.

To better characterize the changes in reward processing, I was interested in whether the onset of puberty alters how the nucleus accumbens interacts with the rest of the brain when a person anticipates a reward. As part of a large scale, NIMH longitudinal study of pubertal neuro development, I study typically developing children and adolescents between the ages of 8 and 18 in eight to 10-month intervals. At each visit, participants complete a comprehensive neuro imaging protocol and clinical assessments including characterization of puberty endocrine events and physician determine puberty status. To study reward related changes in brain function during puberty, I analyzed data from a reward processing game and compared brain connectivity of our prepubescent 8-year-old children with a cohort of 12-year-old adolescents in a preliminary cross-sectional design. Because I was specifically interested in nucleus accumbens activity during reward, I use it as a seed region to probe its functional interactions across the whole brain.

I found that functional connectivity between the nucleus accumbens and two brain regions, including the hippocampus and right inferior frontal gyrus differed between children and adolescents. Specifically, I found that pre-pubertal children showed minimal connectivity between the nucleus accumbens and both of these regions, while adolescence showed that as nucleus accumbens activity increased, hippocampus and frontal gyrus activity decreased. These data provide preliminary evidence of changes in reward related functional connectivity with the nucleus accumbens from pre to post onset of puberty, which may contribute to the increased impulsive behaviors observed during this critical developmental period. However, using this cross-sectional design, we cannot associate the impact of puberty related hormonal events from those that age. We are currently collecting longitudinal data and future analysis will attempt to disentangle the roles of age, puberty stage, and hormonal events of puberty in the development of reward processing.