Introduction

Cognitive Map Theory predicts that the hippocampus (HPC) plays a specialized, time-invariant role in supporting allocentric spatial memory, while Standard Consolidation Theory makes the competing prediction that the HPC plays a time-limited role, with more remote memories gaining independence of HPC function. These theories, however, are largely informed by the results of laboratory-based tests that are unlikely to simulate the demands of representing real-world environments in humans. Validation of these theories is further limited by an overall focus on spatial memory of newly encountered environments and on individuals with extensive lesions to the HPC and to surrounding medial temporal lobe (MTL) regions. The current study incorporates naturalistic tests of spatial memory based on recently and remotely encountered environments navigated by individuals with lesions to the HPC/MTL or that are limited to the HPC's major output, the fornix.

Methods

Four participants with bilateral HPC/MTL and/or fornix lesions drew sketch maps of recently and remotely experienced neighbourhoods and houses. Tests of the appearance, distances, and routes between landmarks from the same real-world environments were also administered. Performance on the tasks was compared to that of control participants closely matched in terms of exposure to the same neighbourhoods and home environments as well as to actual maps.

Results

The performance of individuals with fornix/MTL lesions was found to be largely comparable to that of controls on objective tests of spatial memory, other than one case who was impaired on remote and recent conditions for several tasks. The nature of deficits in recent and remote spatial memory were further revealed on house floorplan drawings, which contained spatial distortions, room/structure transpositions, and omissions, and on neighbourhood sketch maps, which were intact in terms of overall layout but sparse in details such as landmarks.

Conclusion

Lab-based tests of spatial memory of newly learned environments are unlikely to fully capture patterns of spared and impaired representations of real-world environments (e.g., peripheral features, configurations). Naturalistic tasks, including generative drawing tasks, indicate that contrary to Cognitive Map Theory, neither HPC nor MTL are critical for allocentric gross representations of large-scale environments. Conversely, the HPC appears critical for representing detailed spatial information of local naturalistic environments and environmental objects regardless of the age of the memory, contrary to Standard Consolidation Theory.

中文翻译：

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海马和穹窿病变后远期和近期空间记忆中保留要点的贫乏细节

介绍

认知图谱理论预测，海马体 (HPC) 在支持异中心空间记忆方面发挥着专门的、时间不变的作用，而标准巩固理论则做出了相互竞争的预测，即 HPC 发挥着时间有限的作用，更多的远程记忆将获得 HPC 的独立性功能。然而，这些理论很大程度上是基于实验室测试的结果，这些测试不太可能模拟代表人类真实世界环境的需求。这些理论的验证进一步受到对新遇到环境的空间记忆以及对 HPC 和周围内侧颞叶 (MTL) 区域有广泛损伤的个体的总体关注的限制。目前的研究结合了空间记忆的自然测试，该测试基于最近和远程遇到的环境，这些环境是由 HPC/MTL 受损或仅限于 HPC 的主要输出（穹窿）的个体导航的。

方法

四名患有双侧 HPC/MTL 和/或穹窿病变的参与者绘制了最近和远程经历的社区和房屋的草图。还对来自相同真实环境的地标之间的外观、距离和路线进行了测试。将这些任务的表现与对照组参与者的表现进行比较，这些参与者在接触相同的社区和家庭环境以及实际地图方面非常匹配。

结果

在空间记忆客观测试中，发现患有穹窿/MTL损伤的个体的表现在很大程度上与对照组相当，除了一名在多项任务的远程和近期条件下受损的病例之外。近期和远期空间记忆缺陷的本质在房屋平面图上得到了进一步揭示，其中包含空间扭曲、房间/结构换位和遗漏，以及邻里草图，这些草图在总体布局方面完好无损，但细节稀疏，例如作为地标。

结论

基于实验室的新学习环境的空间记忆测试不太可能完全捕获真实世界环境（例如，外围特征、配置）的幸存和受损表示的模式。自然任务（包括生成绘图任务）表明，与认知图理论相反，HPC 和 MTL 对于大规模环境的异中心总体表示都不是至关重要的。相反，无论记忆的年龄如何，高性能计算对于表示当地自然环境和环境物体的详细空间信息似乎至关重要，这与标准巩固理论相反。