Fear conditioning and affective modulation of the startle reflex in male adolescents with early-onset or adolescence-onset conduct disorder and healthy control subjects

Background: Impairments in emotional processing may play an etiological role in the development of aggressive or antisocial behavior such as is seen in conduct disorder (CD). These findings may be developmentally sensitive, with neuropsychological impairments confined to those with the early-onset form of CD, which emerges in childhood. We investigated whether adolescents with early- or adolescenceonset CD would acquire fear conditioned responses to a visual conditioned stimulus and show a normal pattern of affective modulation of the startle reflex. Methods: Electrodermal activity was measured during the fear conditioning process, and electromyographic recording methods were used to assess blink magnitudes elicited by acoustic startle probes during the viewing of emotionally valenced pictures. Forty-one early-onset CD, 28 adolescence-onset CD, and 54 healthy control adolescents participated in the study. Results: Both CD groups showed impaired differential fear conditioning relative to control subjects, while retaining the ability to generate normal skin conductance responses to the aversive unconditioned stimulus. There was a similar relationship between emotional valence of the slides and startle magnitude in CD and control adolescents, but startle-elicited blinks were lower across all emotion categories in both CD subtypes. Conclusions: Fear conditioning deficits and reduced startle amplitudes were observed in participants with early- and adolescence-onset forms of CD. These findings are consistent with impairments in neural systems subserving emotion and involving the amygdala in CD, regardless of age of onset