Interactions between the representations of pain and reward suggest dynamic shifts in reference point

Abstract

With an aim to understand how brains compute the expected utility of mixed prospects, namely those associated with both negative and positive attributes, we designed a task which equated the opportunity to learn about these attributes and their hedonic value. Participants underwent fMRI scanning while they experienced a classical conditioning paradigm where emotionally-neutral faces predicted a probability of pain and reward conforming to a 2 (Electric Pain: high, low) x 2 (Monetary Reward: high, low) factorial design. We found a robust interaction between the anticipation of pain and reward in the BOLD signal. Analysis of simple effects revealed that sensitivity to each attribute increased under high levels of the other attribute. In the bilateral insula and mid-cingulate gyrus sensitivity to pain was greater under high reward, and in the OFC, caudate, ventral striatum and VTA sensitivity to reward was greater under high pain. We speculate that this pattern is due to dynamic shifts in the reference point participants considered to evaluate each attribute.