Episodic integration under stress

独立事件与情节的整合是情节-自传体记忆的一个基本过程。最近的研究表明，这种整合是由内侧前额叶皮质(MPFC)和海马体介导的，海马体的不同亚区代表不同抽象程度的事件。MPFC和海马体都对应激事件高度敏感，应激时释放的荷尔蒙和神经递质也会释放出来；压力被认为会减少这些区域的活动。应激是否影响事件与情节的整合，以及哪些神经机制参与了假定的应激效应，目前还完全不清楚，尽管这个问题对应用环境也有相当大的影响。我们假设，应激损害了事件与情节的整合以及支持这种整合的神经过程，主要是在mPFC和海马体。更具体地说，我们预测，在深入了解以前无关事件的关系后，应激将减少海马区的错配反应和海马区-前额叶的重组。此外，我们假设应激导致沿着海马体长轴的情节关系的等级表征的减少。这些应激诱导的变化应该会在一周后导致对编码的情节及其关系的记忆受损。为了验证这些假说，健康的志愿者在完成核磁共振扫描仪中探索情节整合过程的任务之前，将暴露在压力源或控制操作中。在任务完成后以及一周后，将立即测试成功的集成。除了它们对我们对情节-自传体记忆的总体理解具有至关重要的相关性之外，这个项目的发现可能对与压力相关的精神障碍有重要的影响，例如创伤后应激障碍，在高压力条件下编码的事件的分裂和碎片化记忆是非常常见的。

The integration of separate events to episodes is a fundamental process for episodic-autobiographical memory. Recent research shows that this integration is critically mediated by the medial prefrontal cortex (mPFC) and hippocampus, with different subregions of the hippocampus representing episodes at a different degree of abstraction. Both the mPFC and the hippocampus are highly sensitive to stressful events and the hormones and neurotransmitters that are released in response to stressful encounters; stress is thought to reduce the activity in those areas. Whether stress affects the integration of events to episodes and which neural mechanisms are involved in the putative stress effect is completely unknown, despite the considerable implications of this issue, also for applied contexts. We hypothesize that stress impairs the integration of events to episodes and the neural processes supporting this integration, mainly in the mPFC and hippocampus. More specifically, we predict that stress will reduce the hippocampal mismatch-reaction and the hippocampal-prefrontal reorganization after insight into the relationship of previously unrelated episodes. Furthermore, we assume a stress-induced decrease in the hierarchical representation of episodic relationships along the hippocampal long axis. These stress-induced changes should result in impaired memory for the encoded episodes and their relationships after one week. In order to test these hypotheses, healthy volunteers will be exposed to a stressor or a control manipulation before they complete, in a MRI scanner, a task that probes episodic integration processes. The successful integration is tested immediately after the task as well as one week later. Beyond their crucial relevance for our understanding of episodic-autobiographical memory in general, the findings of this project might have important implications for stress-related mental disorders, such as post-traumatic stress disorder, in which disintegrated and fragmented memories for events encoded under high stress conditions are very common.