Stress effects on reward circuitry in early childhood

• In Event: 1-218 - How the Environment Shapes Learning Across Development

Integrative Statement

Exposure to early life stress has been linked to disruptions in reward processing. A recent study in animal models demonstrated that early life stress alters gene expression in the ventral tegmental area (VTA), and that these gene expression changes were both necessary, and sufficient, to cause impairments in reward processing (Peña et al., 2017). Inspired by this evidence from animal models, we examined whether chronic stress exposure in young children (N = 38, ages 4-7) is associated with VTA connectivity, and whether differences in VTA connectivity explain links between early life stress exposure and the ability to inhibit impulses in the face of rewards. To assess chronic stress in the home, parents were asked to self-report on their perceived stress levels during the previous month. To assess VTA connectivity, we conducted a resting-state functional magnetic resonance imaging analysis using VTA as the seed. To assess reward sensitivity and inhibitory control, participants completed the marshmallow task. In the marshmallow task, children are told that they will be given a larger treat if they can wait for the experimenter to return, and that they can have a smaller treat at any time if they choose not to wait.

Greater chronic stress in the home was significantly related to reduced delay of gratification in children (see Figure). Greater chronic stress exposure was associated with decreased connectivity between the VTA and a region of left hippocampus. Connectivity between the VTA and bilateral hippocampus, defined anatomically, significantly mediated the relationship between chronic stress exposure and delay of gratification. In other words, greater chronic stress was associated with decreased VTA-hippocampus connectivity, which was associated with less successful inhibition, or greater sensitivity to immediate rewards. These results suggest that chronic stress exposure in early childhood shapes connectivity between VTA and the hippocampus, impacting inhibitory control and reward processing. Activation of the hippocampus and VTA has previously been linked to reward-related motivation, including better episodic memory performance as a function of greater anticipation for future rewards (Adcock et al., 2006; Shohamy & Adcock, 2010). More broadly, VTA-hippocampus connectivity has been linked to learning and memory for novel, important information (Lisman & Grace, 2005; Marusak et al., 2017). Future research involving a broader array of cognitive measures, including attention, motivation, and learning, is necessary to understand how stress-induced changes in VTA connectivity influence cognitive development.

Authors

• Anne T. Park, University of Pennsylvania
  Presenting Author

• Allyson Mackey, University of Pennsylvania
  Non-Presenting Author