Looming stimuli are processed as threatening and activate basic neural defense systems. However, it is unclear how animacy information modulates this response. Participants (N = 25) viewed threatening or neutral images that were either animate (animals) or inanimate (objects) and which either approached (loomed) or receded from the participant. The amygdala was responsive to emotional, animacy and looming information (particularly to looming threats and looming animate stimuli). Periaqueductal gray was also sensitive to emotional information and particularly responsive to looming threats. The data are interpreted within category specific models of the amygdala and temporal cortex.
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The current study examined temporal discounting (the decrease in subjective reward value as a function of increasing delay) in youths with conduct disorder (CD) and the extent to which this was modulated by level of psychopathic traits. In the temporal discounting task, participants were asked to choose between immediate rewards of varying values and a larger reward, held at a constant value ($10), whose receipt was delayed by different time intervals across trials (e.g., 7 days, 360 days). The level of immediate reward necessary for selection over the larger, delayed reward is the measure of temporal discounting. Forty-six youths (21 with CD and 25 healthy youths) participated in this study. Compared with healthy youths, youths with CD chose significantly smaller amounts of immediate reward rather than the larger future rewards. This was the case even in youths with CD without comorbid attention-deficit/hyperactivity disorder. However, level of psychopathic traits did not modulate temporal discounting in this sample. These results are discussed in terms of neurobiological models of CD and psychopathic traits.
Decades of research have shown that youths with disruptive behavior disorders (DBD) are a heterogeneous population. Over the past 20 years, researchers have distinguished youths with DBD as those displaying high (DBD/HCU) versus low (DBD/LCU) callous-unemotional (CU) traits. These traits include flat affect and reduced empathy and remorse, and are associated with more severe, varied, and persistent patterns of antisocial behavior and aggression. Conduct problems in youths with HCU and LCU are thought to reflect distinct causal vulnerabilities, with antisocial behavior in youths with DBD/HCU reflecting a predominantly genetic etiology, while antisocial behavior in youths with DBD/LCU is associated primarily with environmental influences. Here we selectively review recent functional (fMRI) and structural (sMRI) magnetic resonance imaging research on DBD, focusing particularly on the role of CU traits. First, fMRI studies examining the neural correlates of affective stimuli, emotional face processing, empathy, theory of mind, morality, and decision-making in DBD are discussed. This is followed by a review of the studies investigating brain structure and structural connectivity in DBD. Next, we highlight the need to further investigate females and the role of sex differences in this population. We conclude the review by identifying potential clinical implications of this research.
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