Terpou Braeden A, Densmore Maria, Théberge Jean, Thome Janine, Frewen Paul, McKinnon Margaret C, Lanius Ruth A
Department of Neuroscience, Western University, London, ON, Canada.
Department of Psychiatry, Western University, London, ON, Canada.
Chronic Stress (Thousand Oaks). 2019 Sep 5;3:2470547019871369. doi: 10.1177/2470547019871369. eCollection 2019 Jan-Dec.
The innate alarm system consists of a subcortical network of interconnected midbrain, lower brainstem, and thalamic nuclei, which together mediate the detection of evolutionarily-relevant stimuli. The periaqueductal gray is a midbrain structure innervated by the innate alarm system that coordinates the expression of defensive states following threat detection. In participants with post-traumatic stress disorder, the periaqueductal gray displays overactivation during the subliminal presentation of trauma-related stimuli as well as altered resting-state functional connectivity. Aberrant functional connectivity is also reported in post-traumatic stress disorder for the default-mode network, a large-scale brain network recruited during self-referential processing and autobiographical memory. Here, research lacks investigation on the extent to which functional interactions are displayed between the midbrain and the large-scale cortical networks in post-traumatic stress disorder.
Using a subliminal threat presentation paradigm, we investigated psycho-physiological interactions during functional neuroimaging in participants with post-traumatic stress disorder (n = 26) and healthy control subjects (n = 20). Functional connectivity of the periaqueductal gray was investigated across the whole-brain of each participant during subliminal exposure to trauma-related and neutral word stimuli.
As compared to controls during subliminal threat presentation, the post-traumatic stress disorder group showed significantly greater periaqueductal gray functional connectivity with regions of the default-mode network (i.e., angular gyrus, precuneus, superior frontal gyrus). Moreover, multiple regression analyses revealed that the functional connectivity between the periaqueductal gray and the regions of the default-mode network correlated positively to symptoms of avoidance and state dissociation in post-traumatic stress disorder.
Given that the periaqueductal gray engages the expression of defensive states, stronger midbrain functional coupling with the default-mode network may have clinical implications to self-referential and trauma-related processing in participants with post-traumatic stress disorder.
先天警报系统由中脑、低位脑干和丘脑核团相互连接构成的皮质下网络组成，这些结构共同介导对具有进化相关性刺激的检测。导水管周围灰质是中脑结构，受先天警报系统支配，在威胁检测后协调防御状态的表达。在创伤后应激障碍患者中，导水管周围灰质在创伤相关刺激的阈下呈现期间表现出过度激活，以及静息态功能连接改变。创伤后应激障碍患者的默认模式网络（一种在自我参照加工和自传体记忆过程中被激活的大规模脑网络）也存在异常功能连接。目前，关于创伤后应激障碍患者中脑与大规模皮质网络之间功能相互作用程度的研究尚少。
我们采用阈下威胁呈现范式，对创伤后应激障碍患者（n = 26）和健康对照者（n = 20）进行功能神经成像研究，以探讨心理生理相互作用。在阈下暴露于创伤相关和中性词刺激期间，对每位参与者全脑的导水管周围灰质功能连接进行研究。
与阈下威胁呈现期间的对照组相比，创伤后应激障碍组与默认模式网络区域（即角回、楔前叶、额上回）的导水管周围灰质功能连接显著增强。此外，多元回归分析显示，导水管周围灰质与默认模式网络区域之间的功能连接与创伤后应激障碍的回避和状态解离症状呈正相关。
鉴于导水管周围灰质参与防御状态的表达，中脑与默认模式网络更强的功能耦合可能对创伤后应激障碍患者的自我参照和创伤相关加工具有临床意义。
