Interaction of Home Food Environment and Ability to Delay Reward on Dopamine 1 Receptor Signaling

Background: Delay of gratification (DG), the ability to inhibit rewardseeking, predicts body mass index. The external food environment influences DG, with high-reward environments (many highly palatable foods available) enhancing the ability to delay reward. Spontaneous eye blink rate (sEBR), a proxy of dopamine 1 receptor (D1R) signaling, is thought to reflect reward-seeking strategies. We hypothesized a reward-rich environment would be related to increased sEBR in children exhibiting long DG, whereas a reward-poor environment would be related to lower sEBR in children with short DG. Methods: 64 children (age 3.54± 0.21y, BMI% 52± 27%, 29 male, 35 female) performed an eye tracking task, delay of gratification task (marshmallow task), and their mothers completed a home food inventory. Reward environment was calculated as the sum of highly processed foods in the home. DG was categorized based on wait time for a treat with a maximum wait time of 420 sec: short DG (n=27, wait 100 sec), medium DG (n=17, 100 sec < wait 399 sec), and long DG (n=20, wait > 399 sec). sEBR was calculated as the total blinks over a 7-minute food and control image eye tracking task. We used a linear model to assess the relationship between sEBR and reward environment by DG interaction controlling for BMI%, child sex, and age. Dummy coding compared the medium and long groups to the low (reference) with the intercept as the cell mean of the reference group. Results: Children in the long DG group showed a negative relationship between sEBR and reward environment compared to children in the short DG (β= -0.50, SE = 0.11, p = 0.05). Conclusions: Contrary to our hypothesis, a high-reward environment correlated with lower D1R signaling in children with long DG. This result suggests a devaluation of highly palatable food in the reward-rich environment where the reward can be gained in the absence of an appropriate drive state. Our findings emphasize the importance of the external food environment on reward behavior.