Addis Donna Rose, Schacter Daniel L
Department of Psychology, Harvard University, Cambridge, Massachusetts 02138, USA.
Hippocampus. 2008;18(2):227-37. doi: 10.1002/hipo.20405.
Behavioral, lesion and neuroimaging evidence show striking commonalities between remembering past events and imagining future events. In a recent event-related fMRI study, we instructed participants to construct a past or future event in response to a cue. Once an event was in mind, participants made a button press, then generated details (elaboration) and rated them. The elaboration of past and future events recruited a common neural network. However, regions within this network may respond differentially to event characteristics, such as the amount of detail generated and temporal distance, depending on whether the event is in the past or future. To investigate this further, we conducted parametric modulation analyses, with temporal distance and detail as covariates, and focused on the medial temporal lobes and frontopolar cortex. The analysis of detail (independent of temporal distance) showed that the left posterior hippocampus was responsive to the amount of detail comprising both past and future events. In contrast, the left anterior hippocampus responded differentially to the amount of detail comprising future events, possibly reflecting the recombination of details into a novel future event. The analysis of temporal distance revealed that the increasing recency of past events correlated with activity in the right parahippocampus gyrus (Brodmann area (BA) 35/36), while activity in the bilateral hippocampus was significantly correlated with the increasing remoteness of future events. We propose that the hippocampal response to the distance of future events reflects the increasing disparateness of details likely included in remote future events, and the intensive relational processing required for integrating such details into a coherent episodic simulation of the future. These findings provide further support for the constructive episodic simulation hypothesis (Schacter and Addis (2007) Philos Trans R Soc Lond B Biol Sci 362:773-786) and highlight the involvement of the hippocampus in relational processing during elaboration of future events.
行为、损伤和神经影像学证据表明，记忆过去事件和想象未来事件之间存在显著的共性。在最近一项与事件相关的功能磁共振成像研究中，我们指示参与者根据提示构建一个过去或未来的事件。一旦想到一个事件，参与者按下按钮，然后生成细节（详述）并对其进行评分。对过去和未来事件的详述激活了一个共同的神经网络。然而，该网络中的区域可能会根据事件是过去还是未来，对事件特征（如生成的细节数量和时间距离）做出不同反应。为了进一步研究这一点，我们进行了参数调制分析，将时间距离和细节作为协变量，并重点关注内侧颞叶和额极皮层。对细节（与时间距离无关）的分析表明，左后海马体对构成过去和未来事件的细节数量有反应。相比之下，左前海马体对构成未来事件的细节数量有不同反应，这可能反映了将细节重新组合成一个新颖的未来事件。对时间距离的分析表明，过去事件的近期性增加与右侧海马旁回（布罗德曼区域（BA）35/36）的活动相关，而双侧海马体的活动与未来事件的遥远性增加显著相关。我们提出，海马体对未来事件距离的反应反映了遥远未来事件可能包含的细节差异越来越大，以及将这些细节整合到一个连贯的未来情景模拟中所需的密集关系处理。这些发现为建构性情景模拟假说（沙克特和阿迪斯（2007年）《英国皇家学会哲学学报B辑：生物科学》362:773 - 786）提供了进一步支持，并突出了海马体在未来事件详述过程中对关系处理的参与。
