Physical proximity to a traumatic event increases the severity of accompanying stress symptoms, an effect that is reminiscent of evolutionarily configured fear responses based on threat imminence. Despite being widely adopted as a model system for stress and anxiety disorders, fear-conditioning research has not yet characterized how threat proximity impacts the mechanisms of fear acquisition and extinction in the human brain. We used three-dimensional (3D) virtual reality technology to manipulate the egocentric distance of conspecific threats while healthy adult participants navigated virtual worlds during functional magnetic resonance imaging (fMRI). Consistent with theoretical predictions, proximal threats enhanced fear acquisition by shifting conditioned learning from cognitive to reactive fear circuits in the brain and reducing amygdala–cortical connectivity during both fear acquisition and extinction. With an analysis of representational pattern similarity between the acquisition and extinction phases, we further demonstrate that proximal threats impaired extinction efficacy via persistent multivariate representations of conditioned learning in the cerebellum, which predicted susceptibility to later fear reinstatement. These results show that conditioned threats encountered in close proximity are more resistant to extinction learning and suggest that the canonical neural circuitry typically associated with fear learning requires additional consideration of a more reactive neural fear system to fully account for this effect.

物理上接近创伤事件会增加伴随的压力症状的严重性，这种影响使人联想到基于威胁迫在眉睫的进化式恐惧反应。尽管恐惧条件调节研究已被广泛用作压力和焦虑症的模型系统，但尚未描述威胁邻近性如何影响人脑恐惧获取和消灭机制。我们使用三维（3D）虚拟现实技术来操纵特定威胁的自我中心距离，而健康的成年参与者在功能磁共振成像（fMRI）期间导航虚拟世界。与理论预测一致，近端威胁通过将条件学习从大脑的认知转移到反应性恐惧回路，并在恐惧获取和消退过程中减少杏仁核-皮层的连通性，增强了恐惧的获取。通过分析获取阶段和灭绝阶段之间的表征模式相似性，我们进一步证明近端威胁通过小脑中条件学习的持续多变量表示削弱了灭绝效果，从而预测了以后恐惧恢复的易感性。这些结果表明，在近距离遇到的条件性威胁对灭绝学习的抵抗力更强，并且表明通常与恐惧学习相关的规范神经回路需要另外考虑反应性更强的神经恐惧系统，才能充分说明这种影响。