Does the male sex hormone, testosterone, make women more aggressive? To test this hypothesis, Hermans et al.
(pages 263–270) used functional magnetic resonance imaging (fMRI) to assess neural responses to socially threatening stimuli, essentially pictures of angry faces in healthy women. Women with higher testosterone levels showed greater brain activation in regions implicated in aggression, and emotional behavior generally, including the amygdala, hypothalamus, and OFC. The administration of testosterone accentuated the activation of these brain regions in response to the angry faces. Thus, testosterone may play an important role in the response to threat in women, as in men.
Halasz et al.
(pages 271–278) suggest a new mechanism to explore for the treatment of aggression problems in humans. Until very recently, the clinical significance of the neurokinin chemical messenger system was poorly understood. The authors now show that neurons that have receptors for one subtype of neurokinin receptor, neurokinin 1 (NK1) are activated during aggressive encounters in animals. The administration of a NK1 receptor antagonist reduced the behavioral and physiologic signs of aggression. Importantly, this drug reduced a particularly violent form of aggression where one animal physically harmed another animal that intruded into its home space, without disrupting normal behavior.
Fairchild et al.
(pages 279–285) provide new support for the theory that adolescents with conduct disorder (CD) are less inhibited by the anticipation that their misbehavior might be punished and less motivated by delayed rewards. To explore one component of this hypothesis, the authors studied adolescents with CD. Although the adolescents with CD responded normally to an unpleasant noise, they showed a reduced capacity to learn danger cues (predictors of the noise) and safety cues (predictors of no noise), as measured by changes in the magnitude of their startle responses. These findings highlight a potential obstacle for treatment strategies for CD based upon learning theory.