Functional Architecture of Memory Unit, Mercator Research Group, Faculty of Medicine, Ruhr University Bochum, 44801 Bochum, Germany.
Hippocampus. 2013 Dec;23(12):1425-38. doi: 10.1002/hipo.22195. Epub 2013 Sep 18.
According to the "two streams" hypothesis, the lateral entorhinal (LEC) and the perirhinal (PrC) cortices process information related to items (a "what" stream), the postrhinal (POR) and the medial entorhinal cortices (MEC) process spatial information (a "where" stream), and both types of information are integrated in the hippocampus (HIP). However, within the framework of memory function, only the HIP is reliably shown to preferentially process spatial information, and the PrC items' features. In contrast, the role of the LEC and MEC in memory is virtually unexplored, and conflicting results emerge for the POR. Moreover, the specific contribution of the hippocampal subfields CA1 and CA3 to spatial and non-spatial memory is not thoroughly understood. To investigate which of these areas is specifically tuned to spatial demands or stimulus identity (odor or object), we assessed the pattern of activation of these areas during recognition memory by detecting the immediate-early gene Arc, commonly used as a marker of neuronal activation. We report that all MTL areas were recruited during the spatial and the non-spatial tasks. However, the LEC, MEC, POR, and CA1 were activated to a comparable level in spatial and non-spatial tasks, while the PrC was tuned to stimulus-type, not spatial demands, and CA3 to spatial demands but not stimulus-type. Results are discussed within the frame of a recent model suggesting that the MTL could be segregated in terms of memory processes, such as recollection and familiarity, rather than information content.
根据“双流”假说，外侧内嗅皮层（LEC）和旁内嗅皮层（PrC）处理与项目相关的信息（“什么”流），后内嗅皮层（POR）和内嗅皮层（MEC）处理空间信息（“哪里”流），两种类型的信息都在海马体（HIP）中整合。然而，在记忆功能的框架内，只有 HIP 被可靠地证明优先处理空间信息和 PrC 项目的特征。相比之下，LEC 和 MEC 在记忆中的作用几乎没有被探索，而 POR 的结果则存在冲突。此外，海马体亚区 CA1 和 CA3 对空间和非空间记忆的特定贡献也没有被彻底理解。为了研究这些区域中哪些区域专门适应空间需求或刺激身份（气味或物体），我们通过检测即时早期基因 Arc 来评估这些区域在识别记忆过程中的激活模式，Arc 通常被用作神经元激活的标志物。我们报告说，所有 MTL 区域都在空间和非空间任务中被招募。然而，LEC、MEC、POR 和 CA1 在空间和非空间任务中的激活水平相当，而 PrC 则适应于刺激类型，而不是空间需求，CA3 则适应于空间需求，而不是刺激类型。结果在最近提出的一个模型框架内进行了讨论，该模型表明，MTL 可以根据记忆过程（如回忆和熟悉度）而不是信息内容进行分离。
