Department of Psychology, Harvard University, Cambridge, Massachusetts, 02138.
Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany.
Hippocampus. 2017 Dec;27(12):1275-1284. doi: 10.1002/hipo.22796. Epub 2017 Sep 12.
The hippocampus has been consistently associated with episodic simulation (i.e., the mental construction of a possible future episode). In a recent study, we identified an anterior-posterior temporal dissociation within the hippocampus during simulation. Specifically, transient simulation-related activity occurred in relatively posterior portions of the hippocampus and sustained activity occurred in anterior portions. In line with previous theoretical proposals of hippocampal function during simulation, the posterior hippocampal activity was interpreted as reflecting a transient retrieval process for the episodic details necessary to construct an episode. In contrast, the sustained anterior hippocampal activity was interpreted as reflecting the continual recruitment of encoding and/or relational processing associated with a simulation. In the present study, we provide a direct test of these interpretations by conducting a subsequent memory analysis of our previously published data to assess whether successful encoding during episodic simulation is associated with the anterior hippocampus. Analyses revealed a subsequent memory effect (i.e., later remembered > later forgotten simulations) in the anterior hippocampus. The subsequent memory effect was transient and not sustained. Taken together, the current findings provide further support for a component process model of hippocampal function during simulation. That is, unique regions of the hippocampus support dissociable processes during simulation, which include the transient retrieval of episodic information, the sustained binding of such information into a coherent episode, and the transient encoding of that episode for later retrieval.
海马体一直与情景模拟（即对可能发生的未来情景的心理构建）相关联。在最近的一项研究中，我们在模拟过程中发现了海马体的前后时间分离。具体来说，与模拟相关的瞬时活动发生在海马体的相对后部，而持续活动发生在前部。与之前关于模拟过程中海马体功能的理论假设一致，后部海马体的活动被解释为反映了构建情景所需的情景细节的瞬时检索过程。相比之下，持续的前部海马体活动被解释为反映了与模拟相关的编码和/或关系处理的持续招募。在本研究中，我们通过对先前发表的数据进行后续记忆分析，直接检验了这些解释，以评估在情景模拟过程中成功编码是否与前部海马体有关。分析显示，前部海马体存在后续记忆效应（即后来记住的>后来遗忘的模拟）。这种后续记忆效应是短暂的，而不是持续的。总的来说，这些发现为模拟过程中海马体功能的成分加工模型提供了进一步的支持。也就是说，海马体的独特区域在模拟过程中支持可分离的过程，包括情景信息的瞬时检索、这种信息的持续整合到一个连贯的情景中，以及该情景的瞬时编码以备以后检索。
