The medial temporal lobes (MTL) play a prominent role in associative memory processing. Still, it is unclear to what extent specific structures within the MTL sub-serve distinct aspects of associative memory. Here, the role of the MTL in forming spontaneous associations in a "naturalistic" setting is investigated applying a word-list memory test not presenting items in an associative fashion. This allows for the differential investigation of item recall and associative binding. Participants included patients with medial temporal lobe epilepsy (mTLE, n = 79) and healthy controls (n = 58). Memory performance in a verbal list-learning paradigm was analyzed by (1) inter-trial repetitions ("binding", i.e., number of word-pairs consistently recalled over two consecutive trials), and (2) single item recall. In patients, behavioral results were correlated with rhinal cortex and hippocampal volumetric data. Results showed that binding was specifically diminished for patients with mTLE during learning and delayed recall. Moreover, binding predicted behavioral differences in item recall. Notably, hippocampal volumes were correlated with item recall during delayed recall, whereas rhinal cortex volumes were correlated with binding during learning. Our results provide evidence that diminished verbal memory in patients with mTLE at least partly can be attributed to functional reductions in spontaneous inter-trial stimulus binding. Moreover, they demonstrate a process-dependent functional dissociation between rhinal cortex and hippocampus for verbal encoding and recall: While the rhinal cortex is mainly engaged in detecting novel associations, the hippocampus primarily subserves consolidation and recall of associations between stimuli. Our study thus advances current models of the sub-specialization of MTL structures and offers novel evidence that memory formation in the MTL is mediated by associative item-processing, even when stimuli are not presented in an associative fashion per se. Thus, our results provide valuable qualitative insights into mechanisms of memory formation and memory failures in patients with MTL dysfunctions.

中文翻译：

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鼻和海马对自发项目间结合和言语记忆的贡献：颞叶癫痫的证据。

内侧颞叶（MTL）在联想记忆处理中起着重要的作用。但是，尚不清楚MTL内的特定结构在多大程度上服务于关联记忆的不同方面。在这里，MTL在“自然”设置中形成自发联想的作用是通过应用单词列表记忆测试（未以关联方式呈现项目）进行调查的。这允许对项目召回和关联绑定进行差异研究。参与者包括颞叶内侧癫痫（mTLE，n = 79）和健康对照（n = 58）。言语学习列表范式中的记忆表现通过（1）反复试验（“绑定”，即在两次连续的试验中一致召回的单词对数量）和（2）单项回忆进行分析。在患者中 行为结果与鼻皮质和海马体积数据相关。结果表明，在学习和延迟回忆期间，mTLE患者的结合被特异地减少了。而且，绑定可以预测项目召回中的行为差异。值得注意的是，海马体积与延迟回忆中的项目回忆相关，而鼻皮质的体积与学习期间的绑定相关。我们的结果提供了证据，证明mTLE患者的言语记忆能力至少部分下降可归因于自发性试验间刺激结合的功能降低。此外，他们还证明了鼻皮质和海马之间的过程依赖性功能分离，可以进行语言编码和记忆：尽管鼻皮质主要用于检测新的关联，海马主要为巩固和恢复刺激之间的联想服务。因此，我们的研究推进了MTL结构亚专业化的当前模型，并提供了新的证据，证明即使MTL中的刺激不是以关联方式呈现，MTL中的记忆形成也是由关联项处理介导的。因此，我们的结果为MTL功能障碍患者的记忆形成和记忆衰竭机制提供了有价值的定性见解。