DuBrow Sarah, Davachi Lila
Department of Psychology and.
Department of Psychology and Center for Neural Science, New York University, New York, New York 10003
J Neurosci. 2014 Oct 15;34(42):13998-4005. doi: 10.1523/JNEUROSCI.2535-14.2014.
Making sense of previous experience requires remembering the order in which events unfolded in time. Prior work has implicated the hippocampus and medial temporal lobe cortex in memory for temporal information associated with individual episodes. However, the processes involved in encoding and retrieving temporal information across extended sequences is relatively poorly understood. Here we used fMRI during the encoding and retrieval of extended sequences to test specific predictions about the type of information used to resolve temporal order and the role of the hippocampus in this process. Participants studied sequences of images of celebrity faces and common objects followed by a recency discrimination test. The main conditions of interest were pairs of items that had been presented with three intervening items, half of which included an intervening category shift. During encoding, hippocampal pattern similarity across intervening items was associated with subsequent successful order memory. To test for evidence of associative retrieval, we trained a classifier to discriminate encoding patterns associated with faces versus objects and applied the classifier on fMRI patterns during recency discrimination. We found evidence that the category content of intervening items was reactivated during recency judgments, and this was related to hippocampal encoding-retrieval similarity. A follow-up behavioral priming experiment revealed additional evidence for intervening item reinstatement during temporal order judgments. Reinstatement did not differ according to whether the items occurred within a single context or across context boundaries. Thus, these data suggest that inter-item associative encoding and retrieval mediated by the hippocampus contribute to temporal order memory.
理解过往经历需要记住事件随时间展开的顺序。先前的研究表明，海马体和内侧颞叶皮质在与单个事件相关的时间信息记忆中发挥作用。然而，对于跨扩展序列编码和检索时间信息所涉及的过程，我们了解得还相对较少。在此，我们在扩展序列的编码和检索过程中使用功能磁共振成像（fMRI），以测试关于用于解析时间顺序的信息类型以及海马体在此过程中作用的具体预测。参与者学习名人和普通物体的图像序列，随后进行近因辨别测试。主要关注的条件是成对的项目，它们之间有三个间隔项目，其中一半包括间隔类别转换。在编码过程中，间隔项目之间的海马体模式相似性与随后成功的顺序记忆相关。为了测试联想检索的证据，我们训练了一个分类器，以区分与面孔和物体相关的编码模式，并在近因辨别期间将该分类器应用于功能磁共振成像模式。我们发现，在近因判断期间，间隔项目的类别内容被重新激活，这与海马体编码 - 检索相似性有关。一项后续的行为启动实验揭示了在时间顺序判断期间间隔项目恢复的更多证据。无论项目是出现在单个情境中还是跨情境边界，恢复情况都没有差异。因此，这些数据表明，由海马体介导的项目间联想编码和检索有助于时间顺序记忆。
