Cognition and Brain Plasticity Group, Bellvitge Biomedical Research Institute (IDIBELL), Hospitalet de Llobregat 08907, Spain; Department of Cognition, Development and Educational Psychology, University of Barcelona, Barcelona 08035, Spain.
Department of Psychology, New York University, New York, NY 10003, USA.
Curr Biol. 2017 Nov 20;27(22):3499-3504.e4. doi: 10.1016/j.cub.2017.09.057. Epub 2017 Nov 9.
Although everyday experiences unfold continuously over time, shifts in context, or event boundaries, can influence how those events come to be represented in memory [1-4]. Specifically, mnemonic binding across sequential representations is more challenging at context shifts, such that successful temporal associations are more likely to be formed within than across contexts [1, 2, 5-9]. However, in order to preserve a subjective sense of continuity, it is important that the memory system bridge temporally adjacent events, even if they occur in seemingly distinct contexts. Here, we used pattern similarity analysis to scalp electroencephalographic (EEG) recordings during a sequential learning task [2, 3] in humans and showed that the detection of event boundaries triggered a rapid memory reinstatement of the just-encoded sequence episode. Memory reactivation was detected rapidly (∼200-800 ms from the onset of the event boundary) and was specific to context shifts that were preceded by an event sequence with episodic content. Memory reinstatement was not observed during the sequential encoding of events within an episode, indicating that memory reactivation was induced specifically upon context shifts. Finally, the degree of neural similarity between neural responses elicited during sequence encoding and at event boundaries correlated positively with participants' ability to later link across sequences of events, suggesting a critical role in binding temporally adjacent events in long-term memory. Current results shed light onto the neural mechanisms that promote episodic encoding not only for information within the event, but also, importantly, in the ability to link across events to create a memory representation of continuous experience.
尽管日常经验会随着时间的推移不断展开，但上下文或事件边界的变化会影响这些事件在记忆中的表现方式[1-4]。具体来说，在上下文变化时，连续表示之间的记忆绑定更具挑战性，因此，在同一上下文中成功形成时间关联的可能性大于跨上下文[1,2,5-9]。然而，为了保持主观上的连续性，记忆系统将时间上相邻的事件联系起来非常重要，即使它们发生在看似不同的上下文中。在这里，我们使用模式相似性分析方法对人类进行的序列学习任务[2,3]中的头皮脑电图（EEG）记录进行了研究，结果表明，事件边界的检测会触发对刚刚编码的序列事件的快速记忆重新激活。记忆再激活被快速检测到（在事件边界开始后约 200-800 毫秒），并且仅针对以下情况发生：事件序列之前存在具有情节内容的事件。在一个情节内的事件的序列编码期间没有观察到记忆重新激活，这表明记忆再激活是在上下文变化时特异性诱导的。最后，在序列编码期间和事件边界处引发的神经反应之间的神经相似性程度与参与者以后跨事件序列进行链接的能力呈正相关，这表明在长时记忆中绑定时间上相邻的事件具有关键作用。当前的结果揭示了促进情节编码的神经机制不仅适用于事件内的信息，而且重要的是，还适用于跨事件链接以创建连续体验的记忆表示的能力。
