Department of Neuroscience, Western University, London, ON, Canada.
Imaging Division, Lawson Health Research Institute, London, ON, Canada; Department of Psychiatry, Western University, London, ON, Canada.
Neuroimage Clin. 2020;27:102345. doi: 10.1016/j.nicl.2020.102345. Epub 2020 Jul 10.
Self-related processes define assorted self-relevant or social-cognitive functions that allow us to gather insight and to draw inferences related to our own mental conditions. Self-related processes are mediated by the default mode network (DMN), which, critically, shows altered functionality in individuals with posttraumatic stress disorder (PTSD). In PTSD, the midbrain periaqueductal gray (PAG) demonstrates stronger functional connectivity with the DMN [i.e., precuneus (PCN), medial prefrontal cortex (mPFC)] as compared to healthy individuals during subliminal, trauma-related stimulus processing. Here, we analyzed the directed functional connectivity between the PAG and the PCN, as well as between the PAG and the mPFC to more explicitly characterize the functional connectivity we have observed previously on the corresponding sample and paradigm. We evaluated three models varying with regard to context-dependent modulatory directions (i.e., bi-directional, bottom-up, top-down) among individuals with PTSD (n = 26) and healthy participants (n = 20), where Bayesian model selection was used to identify the most optimal model for each group. We then compared the effective connectivity strength for each parameter across the models and between our groups using Bayesian model averaging. Bi-directional models were found to be favoured across both groups. In PTSD, we revealed the PAG to show stronger excitatory effective connectivity to the PCN, as well as to the mPFC as compared to controls. In PTSD, we further demonstrated that PAG-mediated effective connectivity to the PCN, as well as to the mPFC were modulated more strongly during subliminal, trauma-related stimulus conditions as compared to controls. Clinical disturbances towards self-related processes are reported widely by participants with PTSD during trauma-related stimulus processing, where altered functional connectivity directed by the PAG to the DMN may elucidate experiential links between self- and trauma-related processing in traumatized individuals.
自我相关过程定义了各种与自我相关或社会认知相关的功能，使我们能够深入了解和推断自己的心理状态。自我相关过程由默认模式网络 (DMN) 介导，而 DMN 在创伤后应激障碍 (PTSD) 患者中的功能发生了改变。在 PTSD 中，与健康个体相比，中脑导水管周围灰质 (PAG) 在潜意识的、与创伤相关的刺激处理过程中与 DMN（即楔前叶 (PCN)、内侧前额叶皮层 (mPFC)）显示出更强的功能连接。在这里，我们分析了 PAG 与 PCN 以及 PAG 与 mPFC 之间的定向功能连接，以更明确地描述我们之前在相应样本和范式中观察到的功能连接。我们评估了三种模型，这些模型在 PTSD 患者 (n=26) 和健康参与者 (n=20) 中具有不同的上下文相关调节方向（即双向、自下而上、自上而下），其中贝叶斯模型选择用于确定每个组的最佳模型。然后，我们使用贝叶斯模型平均法比较了每个模型和两组之间的每个参数的有效连接强度。双向模型在两个组中都受到青睐。在 PTSD 中，我们发现与对照组相比，PAG 对 PCN 以及 mPFC 的兴奋性有效连接更强。在 PTSD 中，我们进一步表明，与对照组相比，PAG 介导的对 PCN 和 mPFC 的有效连接在潜意识的、与创伤相关的刺激条件下受到更强的调节。创伤后应激障碍患者在处理与创伤相关的刺激时，广泛报告了与自我相关过程有关的临床障碍，而由 PAG 到 DMN 的功能连接的改变可能阐明了创伤个体中自我和创伤相关处理之间的体验联系。
