Center for Cognitive Neuroscience, Department of Psychology and Neuroscience, Duke University, Durham, NC 27708, USA.
Cereb Cortex. 2013 Dec;23(12):2818-28. doi: 10.1093/cercor/bhs258. Epub 2012 Sep 11.
A fundamental principle in memory research is that memory is a function of the similarity between encoding and retrieval operations. Consistent with this principle, many neurobiological models of declarative memory assume that memory traces are stored in cortical regions, and the hippocampus facilitates the reactivation of these traces during retrieval. The present investigation tested the novel prediction that encoding-retrieval similarity can be observed and related to memory at the level of individual items. Multivariate representational similarity analysis was applied to functional magnetic resonance imaging data collected during encoding and retrieval of emotional and neutral scenes. Memory success tracked fluctuations in encoding-retrieval similarity across frontal and posterior cortices. Importantly, memory effects in posterior regions reflected increased similarity between item-specific representations during successful recognition. Mediation analyses revealed that the hippocampus mediated the link between cortical similarity and memory success, providing crucial evidence for hippocampal-cortical interactions during retrieval. Finally, because emotional arousal is known to modulate both perceptual and memory processes, similarity effects were compared for emotional and neutral scenes. Emotional arousal was associated with enhanced similarity between encoding and retrieval patterns. These findings speak to the promise of pattern similarity measures for evaluating memory representations and hippocampal-cortical interactions.
记忆研究的一个基本原则是，记忆是编码和检索操作之间相似性的函数。许多陈述性记忆的神经生物学模型都符合这一原则，它们假设记忆痕迹存储在皮质区域，而海马体有助于在检索过程中重新激活这些痕迹。本研究检验了一个新的预测，即可以在单个项目的水平上观察到并将编码-检索相似性与记忆联系起来。多变量代表性相似性分析应用于在情绪和中性场景的编码和检索过程中收集的功能磁共振成像数据。记忆成功追踪了前额叶和后叶皮质之间编码-检索相似性的波动。重要的是，后区的记忆效应反映了在成功识别过程中特定于项目的表示之间相似性的增加。中介分析显示，海马体介导了皮质相似性和记忆成功之间的联系，为检索过程中海马体-皮质相互作用提供了关键证据。最后，因为情绪唤醒已知会调节感知和记忆过程，所以比较了情绪和中性场景的相似性效应。情绪唤醒与编码和检索模式之间相似性的增强有关。这些发现表明，模式相似性度量对于评估记忆表示和海马体-皮质相互作用具有很大的意义。
