Early Experience And The Development Of Dopaminergic Circuitry
early life stress
Neuroscience and Neurobiology
The developing brain is highly malleable, meaning that children are acutely sensitive to their early experiences, for better or for worse. Early adversity significantly increases the risk for psychopathology and learning challenges. Recent work in animal models powerfully suggests that the ventral tegmental area (VTA), a major source of dopaminergic projections to the rest of the brain, is a key mediator for how early stressful experiences can become biologically embedded: in mice, absent or disrupted caregiving results in latent vulnerability of the dopaminergic system to stress well into adulthood. Thus, it may be that early adversity causes a shift in the developmental trajectory of the VTA, with cascading effects on later motivational and socioemotional processes. However, little is known about whether similar disruptions in VTA circuitry are detectable in children. Thus, I leveraged fMRI methods in 4- to 10-year-old children, to examine the functional integrity of dopaminergic circuitry early in development. In Chapter 2, I tested whether stress exposure relates to VTA resting-state functional connectivity. I found an age x stress exposure interaction, such that only children with lower stress exposure showed a positive relationship between age and VTA-mPFC connectivity, consistent with an interpretation that high stress exposure is related to blunted VTA maturation. Chapter 3 examined children’s neural responses to naturalistic emotional content using movie fMRI, and linked to parenting behaviors observed in the lab. I found that children who experienced more negative parenting showed reduced VTA activity during positive emotion scenes. Finally, Chapter 4 examined curiosity, a behavior that is supported by dopaminergic circuitry, and that encourages greater learning by engaging positive interest and intrinsic motivation. I tested whether individual differences in curiosity are reflected in resting-state connectivity patterns, and can be predicted by environmental experiences. Together, this work suggests that early experiences play a critical role in tuning dopaminergic neurocircuitry in children, with potentially enduring consequences for reward and socioemotional processing. This has implications both for education and for policy: how can we protect children in negative environments, and provide positive support that will allow them to best thrive as learners.