Do you make a difference? Social context in a betting task.

Social context strongly influences human motivated behavior. The triadic model implicates three major nodes in the regulation of motivated behavior, i.e. amygdala, medial prefrontal cortex (mPFC) and striatum. The present work examines how social context modulates this system. Nineteen healthy subjects completed an event-related functional magnetic resonance imaging study of a monetary betting task in the presence (social trials) and in the absence of a social peer (nonsocial trials). In the social trials, the scanned subject played along with another subject, although their performances were independent from one another. In the nonsocial trials the scanned subject played alone. Although behavioral performance did not differ between social and nonsocial trials, BOLD signal changes during betting were significantly greater in the amygdala bilaterally and the right dorsolateral prefrontal cortex (BA 9) in the social condition relative to the nonsocial condition. In contrast, activation was greater in ventral striatum in the nonsocial condition relative to the social condition. These findings suggest that social context modulates the triadic neural-systems ensemble to adjust motivated behavior to the unique demands associated with the presence of conspecifics.