Spider phobia is characterized by exaggerated fear of situations where spiders could be present, resulting in avoidance of such situations and compromised quality of life. An important component in psychological treatment of spider phobia is exposure to phobic situations that reduces avoidance behaviors. At the neural level, amygdala responses to phobic material are elevated, but normalizes following exposure treatment. To what extent amygdala activity decreases during a session of repeated phobic stimulation, and whether activity decrease is related to subsequent avoidance is not well studied. We hypothesized reduced amygdala activity during the course of repeated exposure to spider pictures, and that the degree of reduction would predict subsequent avoidance of spider pictures. To test our hypothesis, functional magnetic resonance imaging was performed in 45 individuals with spider fear during repeated exposure to spider pictures. Results showed that repeated exposure to spider stimuli attenuated amygdala reactivity and individual differences in activity reductions predicted subsequent avoidance behavior to spider pictures in an incentive-conflict task, with larger attenuations predicting less avoidance. At 6-month follow up, initial reductions in amygdala activation still predicted avoidance. This result demonstrates that reduction in amygdala responses is related to clinically meaningful outcomes in human anxiety, and suggests that within-session reductions in amygdala responses could be an important mechanism explaining the clinical effects of exposure therapy.

蜘蛛恐惧症的特征是对可能存在蜘蛛的情况过分恐惧，从而避免了这种情况并降低了生活质量。蜘蛛恐惧症的心理治疗中的重要组成部分是暴露于恐惧环境中，这会减少回避行为。在神经水平上，杏仁核对恐惧物质的反应增强，但在暴露治疗后恢复正常。在反复恐惧刺激的过程中杏仁核活性降低到什么程度，以及活性降低是否与随后的回避有关。我们假设在反复暴露于蜘蛛图片的过程中杏仁核活性降低，并且降低的程度将预测随后避免蜘蛛图片。为了检验我们的假设，功能性磁共振成像是在45名患有蜘蛛恐惧症的患者中进行的，这些患者在反复暴露于蜘蛛照片中。结果表明，重复暴露于蜘蛛刺激会减弱杏仁核的反应性，活动减少的个体差异可预测在激励冲突任务中蜘蛛图片的后续回避行为，而较大的衰减则预示着回避的可能性较小。在6个月的随访中，杏仁核激活的最初减少仍预示会避免。该结果表明杏仁核反应的减少与人类焦虑症的临床意义相关，并且表明会话期间杏仁核反应的减少可能是解释暴露疗法临床效果的重要机制。