Background: Individuals with psychopathy have an increased tendency toward certain types of aggression. We hypothesized that successful psychopaths, who have no criminal convictions but can be diagnosed with psychopathy in terms of personality characteristics, are skilled at regulating aggressive impulses, compared to incarcerated unsuccessful psychopaths.
Methods: In this block-designed functional magnetic resonance imaging (fMRI) study, we sought to clarify the neural mechanisms underlying differences in frustration-induced aggression as a function of psychopathy in non-criminal populations. Twenty male undergraduate students who completed a self-report psychopathy questionnaire were scanned while they completed a task in which they either could or could not punish other individuals who made unfair offers of monetary distribution.
Results: Individuals with high psychopathic tendencies were less likely to make a decision to inflict costly punishment on people proposing unfair offers. During this decision-making, psychopathy was associated with less amygdala activity in response to the unfairness of offers. Moreover, the amygdala dysfunction in psychopathic individuals was associated with reduced functional connectivity with dopaminergic-related areas, including the striatum, when punishment was available compared to when it was unavailable.
Limitations: The possibility that levels of psychopathic traits in a regular population were milder than in incarcerated populations cannot be ruled out.
Conclusions: The findings indicate that amygdala dysfunction underlies affective deficits of psychopathy. We propose that the insensitivity of the amygdala to the affective significance of social stimuli contributes to an increased risk of violation of social norms, but enhances the ability to attenuate impulses toward maladaptive aggression in successful psychopaths.
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