Elucidating behavioral and functional connectivity markers of aberrant threat discrimination in PTSD.

Patients with posttraumatic stress disorder (PTSD) tend to over-generalize threat to safe stimuli, potentially reflecting aberrant stimuli discrimination. Yet, it is not clear whether threat overgeneralization reflects general discrimination deficits, or rather a specific bias related to aversive stimuli. Here we tested this question and characterized the neural correlates of threat discrimination. One-hundred and eight participants (33 PTSD; 43 trauma-exposed controls; 32 healthy controls) completed an emotionally neutral complex shape discrimination task involving identifying in 42 similar pairs the previously observed shape; and an emotionally aversive discrimination task, involving providing risk ratings for an aversive conditioned stimulus (CS+), and for several stimuli gradually differing in size from the original CS+. Resting state functional connectivity (rsFC) was collected before completing the tasks. No group differences emerged on the emotionally neutral task. Conversely, on the emotionally aversive task, individuals with PTSD had steeper linear risk rating slopes as the stimuli more resembled the conditioned stimulus. Finally, lower rsFC of amygdala-default mode network (DMN) and DMN-salience network (SN) were associated with steeper risk slopes, while for hippocampus-SN, lower rsFC was found only among participants with PTSD. Individuals with PTSD show deficits in discrimination only when presented with aversive stimuli. Dysregulated discrimination pattern may relate to a lack of input from regulatory brain areas (e.g., DMN/hippocampus) to threat-related brain areas (e.g., SN/amygdala).

创伤后应激障碍（PTSD）患者往往会将威胁过度泛化到安全的刺激上，这可能反映了异常的刺激辨别能力。然而，尚不清楚威胁过度泛化反映的是一般性的辨别缺陷，还是与厌恶刺激相关的特定偏差。在此我们对这一问题进行了测试，并对威胁辨别的神经相关性进行了表征。 108名参与者（33名PTSD患者；43名有创伤暴露的对照组；32名健康对照组）完成了一项情绪中性的复杂形状辨别任务，包括在42对相似图形中识别出之前观察到的形状；以及一项情绪厌恶辨别任务，包括对一个厌恶性条件刺激（CS +）以及几个与原始CS +大小逐渐不同的刺激进行风险评级。在完成任务之前收集了静息态功能连接（rsFC）数据。 在情绪中性任务中未出现组间差异。相反，在情绪厌恶任务中，随着刺激与条件刺激越来越相似，PTSD患者的线性风险评级斜率更陡。最后，杏仁核 - 默认模式网络（DMN）和DMN - 显著网络（SN）的rsFC较低与更陡的风险斜率相关，而对于海马体 - SN，仅在PTSD患者中发现rsFC较低。 PTSD患者仅在面对厌恶刺激时表现出辨别缺陷。失调的辨别模式可能与调节性脑区（例如DMN/海马体）对威胁相关脑区（例如SN/杏仁核）缺乏输入有关。