Fredrikson Mats, Annas Peter, Hettema John M
aDepartment of Psychology, Uppsala University, Uppsala bDepartment of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden cDepartment of Psychiatry, Virginia Institute for Psychiatry and Behavioral Genetics, Virginia Commonwealth University, Richmond, Virginia, USA.
Psychiatr Genet. 2015 Aug;25(4):155-62. doi: 10.1097/YPG.0000000000000088.
OBJECTIVE: Fear conditioning seems to account for the acquisition of post-traumatic stress disorder, whereas conscious recall of events in aftermath of trauma reflects episodic memory. Studies show that both fear conditioning and episodic memory are heritable, but no study has evaluated whether they reflect common or separate genetic factors. To this end, we studied episodic memory and fear conditioning in 173 healthy twin pairs using visual stimuli predicting unconditioned electric shocks. METHODS: Fear conditioning acquisition and extinction was determined using conditioned visual stimuli predicting unconditioned mild electric shocks, whereas electrodermal activity served as the fear learning index. Episodic memory was evaluated using cued recall of pictorial stimuli unrelated to conditioning. We used multivariate structural equation modeling to jointly analyze memory performance and acquisition as well as extinction of fear conditioning. RESULTS: Best-fit twin models estimated moderate genetic loadings for conditioning and memory measures, with no genetic covariation between them. CONCLUSION: Individual differences in fear conditioning and episodic memory reflect distinct genetically influenced processes, suggesting that the genetic risk for learning-induced anxiety disorders includes at least two memory-related genetic factors. These findings are consistent with the facts that the two separate learning forms are distant in their evolutionary development, involve different brain mechanisms, and support that genetically independent memory systems are pivotal in the development and maintenance of syndromes related to fear learning.
目的:恐惧条件反射似乎是创伤后应激障碍形成的原因,而创伤后对事件的有意识回忆反映的是情景记忆。研究表明,恐惧条件反射和情景记忆都具有遗传性,但尚无研究评估它们是反映共同的还是独立的遗传因素。为此,我们使用预测无条件电击的视觉刺激,对173对健康双胞胎进行了情景记忆和恐惧条件反射研究。 方法:使用预测无条件轻度电击的条件视觉刺激来确定恐惧条件反射的习得和消退,而皮肤电活动作为恐惧学习指标。情景记忆通过对与条件反射无关的图片刺激进行线索回忆来评估。我们使用多变量结构方程模型来联合分析记忆表现以及恐惧条件反射的习得和消退。 结果:最佳拟合双胞胎模型估计条件反射和记忆测量的遗传负荷适中,它们之间不存在遗传协变。 结论:恐惧条件反射和情景记忆的个体差异反映了不同的遗传影响过程,这表明学习诱发的焦虑症的遗传风险至少包括两个与记忆相关的遗传因素。这些发现与以下事实一致:这两种不同的学习形式在进化发展上相距甚远,涉及不同的脑机制,并支持遗传上独立的记忆系统在与恐惧学习相关的综合征的发展和维持中起关键作用。
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