衛教新知

【陳姵蓉醫師選讀婦女身心相關文獻】

2018/08/13

摘要:

Posttraumatic stress disorder (PTSD) is widely associated with deficits in extinguishing learned fear responses, which relies on mechanisms of reinforcement learning (e.g., updating expectations based on prediction errors). However, the degree to which PTSD is associated with impairments in general reinforcement learning (i.e., outside of the context of fear stimuli) remains poorly understood. Here, we investigate brain and behavioral differences in general reinforcement learning between adult women with and without a current diagnosis of PTSD. 29 adult females (15 PTSD with exposure to assaultive violence, 14 controls) underwent a neutral reinforcement-learning task (i.e., two arm bandit task) during fMRI. We modeled participant behavior using different adaptations of the Rescorla-Wagner (RW) model and used Independent Component Analysis to identify timecourses for large-scale a priori brain networks. We found that an anticorrelated and risk sensitive RW model best fit participant behavior, with no differences in computational parameters between groups. Women in the PTSD group demonstrated significantly less neural encoding of prediction errors in both a ventral striatum/mPFC and anterior insula network compared to healthy controls. Weakened encoding of prediction errors in the ventral striatum/mPFC and anterior insula during a general reinforcement learning task, outside of the context of fear stimuli, suggests the possibility of a broader conceptualization of learning differences in PTSD than currently proposed in current neurocircuitry models of PTSD.

 

筆者註:

一小規模研究嘗試了解創傷後症候群對非壓力情境下學習能力的影響。相較於控制組(N14),診斷有創傷後症候群的婦女(N=15)在複測紋狀體/內側前額葉皮質(ventral striatum∕medial prefrontal cortex)以及前腦島(anterior insula)對預測誤差(prediction error)的神經編碼(nerual encoding)都有顯著缺損。這暗示了創傷後症候群可能影響經由回饋(reinforcement)而建立的學習能力——即使在非恐懼刺激的情境下——因此可能也一部分地解釋了現有的行為學習治療方式(如暴露法)的限制。