Effects of Dieting on Neural Encoding of Preferences for Edible and Non-Edible Rewards: An ERP Study

The present study investigated whether temporary dieting modulates neural coding of subjective preferences for edible and non-edible rewards. Forty-five dieting and 49 non-dieting healthy adults completed a gambling task while EEG was recorded. In each trial, subjects opened virtual doors to receive individually-rated high, medium, or low preference edible or non-edible rewards. Unexpectedly, dieting did not have an effect on the reward-locked event-related potential (ERP). However, the P2 was generally increased for edible rewards. In contrast, the feedback-related negativity (FRN) was not sensitive to reward type. Preference coding was found in both FRN and P3. It was most pronounced for the P3 frontally, with increased positivity for medium and high relative to low preference, only for edible rewards. Preference coding was less distinct for non-edible rewards, particularly parietally. Further analyses indicated sustained centroparietal preference coding beyond the P3, especially for edible rewards. Taken together, neural coding of subjective preferences seems to be more distinctive for primary compared to secondary rewards, possibly due to increased motivational significance and evaluative processing as well as attentional allocation for primary rewards. The absence of dieting effects indicates that subjective preferences constitute robust, possibly trait-like, phenomena not readily modulated by interventions such as short-term dieting.