Models of memory formation posit that recollection as compared to familiarity-based memory depends critically on the hippocampus, which binds features of an event to its context. For this reason, the contrast between study items that are later recollected versus those that are recognized on the basis of familiarity should reveal electrophysiological patterns in the hippocampus selectively involved in associative memory encoding. Extensive data from studies in rodents support a model in which theta oscillations fulfill this role, but results in humans results have not been as clear. Here, we employed an associative recognition memory procedure to identify hippocampal correlates of successful associative memory encoding and retrieval in patients undergoing intracranial EEG monitoring. We identified a dissociation between 2-5 Hz and 5-9 Hz theta oscillations, by which 2-5 Hz oscillations uniquely were linked with successful associative memory in both the anterior and posterior hippocampus. These oscillations exhibited a significant phase reset that also predicted successful associative encoding, distinguished recollected from familiar items at retrieval, and contributed to reinstatement of encoding-related patterns that distinguished these items. Our results provide direct electrophysiological evidence that 2-5 Hz hippocampal theta oscillations support the encoding and retrieval of memories based on recollection but not familiarity.

中文翻译：

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海马θ振荡支持成功的联想记忆形成

记忆形成的模型认为，与基于熟悉度的记忆相比，记忆的恢复主要取决于海马体，海马体将事件的特征与其背景相关联。由于这个原因，后来被回忆的研究项目与根据熟悉程度被认可的研究项目之间的对比应该揭示选择性参与联想记忆编码的海马体中的电生理模式。来自啮齿类动物研究的大量数据支持一个模型，其中theta振荡可以发挥这种作用，但对人类的结果尚不清楚。在这里，我们采用了联想识别记忆程序，以识别接受颅内脑电图监测的患者成功进行联想记忆编码和检索的海马相关性。我们确定了2-5 Hz和5-9 Hz theta振荡之间的分离，通过这种分离，2-5 Hz振荡独特地与前海马和后海马的成功联想记忆相关联。这些振荡表现出明显的相位重置，该相位重置还预测成功的关联编码，在检索时从熟悉的项目中区分出重新收集，并有助于恢复区分这些项目的与编码相关的模式。我们的结果提供了直接的电生理证据，表明2-5 Hz的海马体theta振荡支持记忆的编码和检索，但并不基于回忆。这些振荡表现出明显的相位重置，该相位重置还预测成功的关联编码，在检索时从熟悉的项目中区分出重新收集，并有助于恢复区分这些项目的与编码相关的模式。我们的结果提供了直接的电生理证据，表明2-5 Hz的海马体theta振荡支持记忆的编码和检索，但并不基于回忆。这些振荡表现出明显的相位重置，该相位重置还预测成功的关联编码，在检索时从熟悉的项目中区分出重新收集，并有助于恢复区分这些项目的与编码相关的模式。我们的结果提供了直接的电生理证据，表明2-5 Hz的海马体theta振荡支持记忆的编码和检索，但并不基于回忆。