How does sad mood affect responses to unfairness in social economic decisions? A neurophysiological investigation.

摘要

Empirical evidence suggests that complex cognitive processes such as decision-making can be influenced by incidental affect (i.e. emotional states unrelated to the decision), which may have importance implications for furthering our understanding and treatment of mood disorders. Following up on previous behavioral findings suggesting that sad mood leads to biases in social decision-making, the present research first investigated how such biases are implemented in the brain. Nineteen adult participants made decisions that involved accepting or rejecting monetary offers from others in an Ultimatum Game (a well known economic task), while undergoing functional magnetic resonance imaging (fMRI). Prior to each set of decisions, participants watched a short video clip aimed at inducing either sadness or a neutral emotional state. Results indicated that sad participants rejected more "unfair" offers than those in the neutral condition, thereby replicating our previous findings. Neuroimaging analyses revealed that receiving unfair offers while in a sad mood elicited activity in brain areas related to aversive emotional states and somatosensory integration (anterior insula) and to cognitive conflict (anterior cingulate cortex). Sad participants also showed a diminished sensitivity in neural regions associated with reward processing (ventral striatum). Importantly, insular activation uniquely mediated the relationship between sadness and decision bias, demonstrating how subtle mood states can be integrated at the neural level to bias decision-making.;In a second study, we assessed to what extent such affect infusion in decision-making may translate to clinical depression, a mood disorder involving chronic sad affect. Fifteen depressed and twenty-three nondepressed individuals made decisions to accept or reject monetary offers from other players in the Ultimatum Game. Like transiently sad, but healthy, individuals, depressed participants reported a more negative emotional reaction to unfair offers. However, unlike sad healthy individuals, they accepted significantly more of these offers than did controls. A positive relationship was observed in the depressed group, but not in controls, between acceptance rates of unfair offers and resting cardiac vagal tone, a physiological index of emotion regulation capacity. These findings suggest distinct biasing processes in depression, which may be related to higher reliance on regulating negative emotion.