Winning smiles: Signalling reward by overlapping and non-overlapping emotional valence differentially affects performance and neural activity.

It is well-known that both emotional and motivational events greatly impact our behaviour. Based on previous work on the interplay between these two constructs, the present study aimed to test whether and how concurrent emotion and reward signals interact in terms of their basic valence, when both are equally relevant to the task. To this end, we employed a novel fMRI paradigm in which reward availability was explicitly signalled by positive, neutral, or negative facial expressions (using block-wise instructions). Hence, in contrast to previous studies combining reward cues with irrelevant emotional stimuli, the present paradigm required participants to process the emotional information in order to respond and receive the reward. Compared to no-reward trials, we found performance benefits in trials in which reward was signalled by positive emotion, and performance detriments in trials in which reward was signalled by negative emotion - even though the reward value of the positive and negative emotion trials was identical. Neurally, reward trials signalled by negative emotion were associated with increased activity in frontal cognitive control regions, indicative of an induced conflict arising from a mismatch in absolute valence between reward and emotion. In contrast, reward trials signalled by positive emotion did not differentially increase activity anywhere in the brain (despite being associated with behavioural facilitation), which seems to support the notion of an inherent, and hence effortless, mapping between positive/rewarding stimuli and approach behaviour. Together, we interpret these patterns in terms of overlapping and non-overlapping valence signals (and associated response tendencies), which can induce benefits and costs, respectively.