Daselaar Sander M, Veltman Dick J, Witter Menno P
Center for Cognitive Neuroscience, Duke University, Box 90999, LSRC Bldg., Rm B243N, Durham, NC 27708, USA.
Hippocampus. 2004;14(2):163-9. doi: 10.1002/hipo.10158.
Lesion studies have provided compelling evidence that episodic memory is dependent on the integrity of the medial temporal lobe (MTL). This role of the MTL in episodic memory has been supported by several neuroimaging studies during both episodic encoding and retrieval. After two meta-analyses of positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) studies, we investigated a possible dissociation within the MTL memory system in relation to encoding and retrieval processes. Based on previous reports that specifically related the function of the MTL in episodic memory to successful encoding and actual recovery of information, we applied event-related fMRI to compare successful encoding of words (ES) directly with successful recognition of those same words (RS). Our results did not indicate a clear dissociation between encoding and retrieval activations in the MTL. Instead, a region in the left MTL, covering the parahippocampal cortex and hippocampal formation, which was activated during ES almost completely overlapped with the area that was activated during RS. An additional region in the left anterior MTL, including the entorhinal cortex, was found to be activated exclusively during ES. Research has indicated that a large percentage of cells in this region are particularly sensitive to the relative novelty of stimuli. Our results, therefore, suggest that the parahippocampal/hippocampal region is involved in the formation and subsequent reactivation of memory traces, whereas the activity observed in the entorhinal cortex may reflect elementary memory processes related to novelty detection.
损伤研究提供了令人信服的证据，表明情景记忆依赖于内侧颞叶（MTL）的完整性。MTL在情景记忆中的这一作用在情景编码和检索过程中的多项神经影像学研究中得到了支持。在对正电子发射断层扫描（PET）和功能磁共振成像（fMRI）研究进行两次荟萃分析之后，我们研究了MTL记忆系统中与编码和检索过程相关的可能分离情况。基于先前将MTL在情景记忆中的功能与信息的成功编码和实际恢复具体联系起来的报告，我们应用事件相关功能磁共振成像直接比较单词的成功编码（ES）与对相同单词的成功识别（RS）。我们的结果并未表明MTL中编码和检索激活之间存在明显的分离。相反，左侧MTL中一个覆盖海马旁皮质和海马结构的区域，在ES期间被激活，几乎与RS期间被激活的区域完全重叠。在左侧MTL前部发现了一个额外的区域，包括内嗅皮质，仅在ES期间被激活。研究表明，该区域中很大比例的细胞对刺激的相对新颖性特别敏感。因此，我们的结果表明，海马旁/海马区域参与记忆痕迹的形成和随后的重新激活，而在内嗅皮质中观察到的活动可能反映了与新颖性检测相关的基本记忆过程。
