[show abstract][hide abstract] ABSTRACT: Humans excel at reciprocal altruism in which two individuals exchange altruistic acts to their mutual advantage. The evolutionary stability of this system depends on recognition of and discrimination against non-reciprocators, and the human mind is apparently specialized for detecting non-reciprocators. Here we investigate the neural response to non-reciprocation of cooperation by imaging human subjects with fMRI as they play an iterated Prisoner's dilemma game with two assumed human partners. Unreciprocated cooperation was associated with greater activity in bilateral anterior insula, left hippocampus and left lingual gyrus, compared with reciprocated cooperation. These areas were also more responsive to unreciprocated cooperation than to unsuccessful risk taking in a non-social context. Finally, functional connectivity between anterior insula and lateral orbitofrontal cortex (OFC) in response to unreciprocated cooperation predicted subsequent defection. The anterior insula is involved in awareness of visceral, autonomic feedback from the body and, in concert with the lateral orbitofrontal cortex, may be responsible for negative feeling states that bias subsequent social decision making against cooperation with a non-reciprocating partner.
[show abstract][hide abstract] ABSTRACT: Little is known about the effects of the menstrual cycle on brain activity in primates. Here, we use 18F-fluorodeoxyglucose positron emission tomography to monitor changes in resting brain glucose metabolism across the menstrual cycle in female rhesus monkeys. Results showed greater activity in right lateral orbitofrontal cortex, a region involved in processing negatively valenced emotional stimuli, in the follicular compared with luteal phase. Estradiol levels were negatively correlated with activity in cortical and brainstem regions involved in emotional processing, and positively correlated with activity in areas involved in cognitive control and emotion regulation. In summary, the data suggest that in primates, fluctuations of ovarian hormones across the menstrual cycle influence activity in brain areas involved in emotion and its regulation.
[show abstract][hide abstract] ABSTRACT: Psychopathy is a disorder involving a failure to experience many emotions that are necessary for appropriate social behavior. In this study, we probed the behavioral, emotional, and neural correlates of psychopathic traits within the context of a dyadic social interaction.
Thirty subjects were imaged with functional magnetic resonance imaging while playing an iterated Prisoner's Dilemma game with human confederates who were outside the scanner. Subjects also completed two self-report psychopathy questionnaires.
Subjects scoring higher on psychopathy, particularly males, defected more often and were less likely to continue cooperating after establishing mutual cooperation with a partner. Further, they experienced more outcomes in which their cooperation was not reciprocated (cooperate-defect outcome). After such outcomes, subjects scoring high in psychopathy showed less amygdala activation, suggesting weaker aversive conditioning to those outcomes. Compared with low-psychopathy subjects, subjects higher in psychopathy also showed weaker activation within orbitofrontal cortex when choosing to cooperate and showed weaker activation within dorsolateral prefrontal and rostral anterior cingulate cortex when choosing to defect.
These findings suggest that whereas subjects scoring low on psychopathy have emotional biases toward cooperation that can only be overcome with effortful cognitive control, subjects scoring high on psychopathy have an opposing bias toward defection that likewise can only be overcome with cognitive effort.