Posttraumatic stress disorder (PTSD) may develop when mechanisms for making accurate distinctions about threat relevance have gone awry. Generalization across conceptually related objects has been hypothesized based on clinical observation in PTSD, but the neural mechanisms remain unexplored. Recent trauma-exposed military veterans (n = 46) were grouped into PTSD (n = 23) and non-PTSD (n = 23). Participants learned to generalize fear across conceptual categories (animals or tools) of semantically related items that were partially reinforced by shock during functional magnetic resonance imaging. Conditioned fear learning was quantified by shock expectancy and skin conductance response (SCR). Relative to veteran controls, PTSD subjects exhibited a stronger neural response associated with fear generalization to the reinforced object category in the striatum, anterior cingulate cortex, amygdala, occipitotemporal cortex, and insula (Z > 2.3; p < 0.05; whole-brain corrected). Based on SCR, both groups generalized the shock contingency to the reinforced conceptual category, but learning was not significantly different between groups. We found that PTSD was associated with an enhanced neural response in fronto-limbic, midline, and occipitotemporal regions to a learned representation of threat that is based on previously established conceptual knowledge of the relationship between basic-level exemplars within a semantic category. Behaviorally, veterans with PTSD were somewhat slower to differentiate threat and safety categories as compared with trauma-exposed veteran controls owing in part to an initial overgeneralized behavioral response to the safe category. These results have implications for understanding how fear spreads across semantically related concepts in PTSD.

当对威胁相关性进行精确区分的机制失灵时，可能会发生创伤后应激障碍（PTSD）。已经基于PTSD中的临床观察假设了概念上相关的对象的泛化，但是神经机制尚待探索。最近受创伤的退伍军人（n  = 46）被分为PTSD（n  = 23）和非PTSD（n = 23）。参与者学会了在语义相关项目的概念类别（动物或工具）中概括恐惧，这些恐惧在功能性磁共振成像过程中受到电击的影响而得到部分增强。有条件的恐惧学习通过休克预期和皮肤电导反应（SCR）进行量化。相对于退伍军人控制，PTSD受试者表现出较强的神经反应，与恐惧普遍化有关，对纹状体，前扣带回皮层，杏仁核，枕颞皮层和岛状区域中的增强对象类别（Z  > 2.3；p <0.05；全脑校正）。两组都基于SCR，将冲击性偶然事件概括为强化的概念类别，但是两组之间的学习并没有显着差异。我们发现，PTSD与额叶，中线和枕颞区域对学习到的威胁表示的神经反应增强有关，后者基于先前建立的语义类别内基本级别示例之间关系的概念知识。在行为上，与创伤暴露的退伍军人控制相比，患有PTSD的退伍军人在区分威胁和安全类别方面要慢一些，部分原因是对安全类别的最初过度概括的行为反应。这些结果对理解恐惧如何在PTSD中的语义相关概念之间传播产生了影响。