Fell Juergen, Ludowig Eva, Rosburg Timm, Axmacher Nikolai, Elger Christian E
Department of Epileptology, University of Bonn, Bonn, Germany.
Neuroimage. 2008 Nov 1;43(2):410-9. doi: 10.1016/j.neuroimage.2008.07.021. Epub 2008 Jul 22.
Lesion and imaging studies have demonstrated that encoding of declarative memories, i.e. consciously accessible events and facts, is supported by processes within the rhinal cortex and the hippocampus, two substructures of the mediotemporal lobe (MTL). Successful memory formation has, for instance, been shown to be accompanied by the rhinal N400 component, followed by a hippocampal positivity, as well as by transient rhinal-hippocampal phase synchronization. However, it has been an open question, which mediotemporal electroencephalogram (EEG) measures predict memory formation most accurately. Therefore, we analyzed and compared the association of different mediotemporal EEG measures with successful memory formation. EEG characteristics were extracted from intracranial rhinal and hippocampal depth recordings in 31 epilepsy patients performing a continuous word recognition paradigm. Classical event-related potential measures, rhinal-hippocampal synchronization, as well as inter-trial phase-locking and power changes within rhinal cortex and hippocampus were evaluated. We found that inter-trial phase-locking is superior to other EEG measures in predicting subsequent memory. This means that memory formation is related to the precise timing of EEG phases within the MTL with respect to stimulus onset. In particular, early rhinal and hippocampal phase-locking in the alpha/beta range reaching its maximum already between 100 and 300 ms after stimulus onset appears to be a precursor of successful memory formation. Our data suggest that early mediotemporal phase adjustments constitute a relevant mechanism underlying declarative memory encoding.
病变和影像学研究表明，陈述性记忆（即有意识可及的事件和事实）的编码由鼻周皮质和海马体中的过程支持，这两个结构是内侧颞叶（MTL）的子结构。例如，成功的记忆形成已被证明伴随着鼻周N400成分，随后是海马体正波，以及鼻周 - 海马体的瞬时相位同步。然而，内侧颞叶脑电图（EEG）测量中哪些能最准确地预测记忆形成一直是个悬而未决的问题。因此，我们分析并比较了不同内侧颞叶EEG测量与成功记忆形成之间的关联。EEG特征是从31名癫痫患者进行连续单词识别范式时的颅内鼻周和海马体深度记录中提取的。评估了经典的事件相关电位测量、鼻周 - 海马体同步，以及鼻周皮质和海马体内的试验间锁相和功率变化。我们发现，试验间锁相在预测后续记忆方面优于其他EEG测量。这意味着记忆形成与内侧颞叶内EEG相位相对于刺激开始的精确时间有关。特别是，在刺激开始后100至300毫秒之间达到最大值的α/β范围内的早期鼻周和海马体锁相似乎是成功记忆形成的先兆。我们的数据表明，早期内侧颞叶相位调整构成了陈述性记忆编码的相关机制。
