Departamento de Psicología Experimental y Fisiología del Comportamiento, Facultad de Psicología, Campus de Cartuja, Universidad de Granada, Granada 18071, Spain.
Neurobiol Learn Mem. 2010 May;93(4):506-14. doi: 10.1016/j.nlm.2010.01.008. Epub 2010 Jan 28.
Several studies have shown that slight modifications in the standard reference spatial memory procedure normally used for allocentric learning in the Morris water maze and the radial maze, can overcome the classic deficit in allocentric navigation typically observed in rats with hippocampal damage. In these special paradigms, however, there is only intramaze manipulation of a salient stimulus. The present study was designed to investigate whether extramaze manipulations produce a similar outcome. With this aim a four-arm plus-shaped maze and a reference spatial memory paradigm were used, in which the goal arm was marked in two ways: by a prominent extramaze cue (intermittent light), which maintained a constant relation with the goal, and by the extramaze constellation of stimuli around the maze. Experiment 1 showed that, unlike the standard version of the task, using this special training procedure hippocampally-damaged rats could learn a place response as quickly as control animals; importantly, one day after reaching criterion, lesioned and control subjects performed the task perfectly during a transfer test in which the salient extramaze stimulus used during the acquisition was removed. However, although acquisition deficit was overcomed in these lesioned animals, a profound deficit in retention was detected 15 days later. Experiment 2 suggests that although under our special paradigm hippocampal rats can learn a place response, spatial memory only can be expressed when the requisites of behavioral flexibility are minimal. These findings suggest that, under certain circumstances, extrahippocampal structures are sufficient for building a coherent allocentric representation of space; however, flexible memory expression is dependent, fundamentally, on hippocampal functioning.
几项研究表明，在 Morris 水迷宫和放射状迷宫中用于非空间参考学习的标准参考空间记忆程序进行轻微修改，可以克服海马损伤大鼠中典型的非空间导航经典缺陷。然而，在这些特殊的范式中，只有在迷宫内对显著刺激进行操作。本研究旨在探讨是否进行迷宫外操作会产生类似的结果。为此，使用了一个四臂加形状的迷宫和一个参考空间记忆范式，其中目标臂通过两种方式标记：通过一个突出的迷宫外线索（间歇性光），它与目标保持恒定关系，以及通过迷宫周围的迷宫外刺激的组合。实验 1 表明，与任务的标准版本不同，使用这种特殊的训练程序，海马损伤大鼠可以像对照动物一样快速学习位置反应；重要的是，在达到标准后一天，损伤和对照受试者在转移测试中表现完美，在转移测试中，在获得过程中使用的显著迷宫外刺激被移除。然而，尽管这些损伤动物克服了获得缺陷，但在 15 天后检测到了严重的保留缺陷。实验 2 表明，尽管在我们的特殊范式下，海马损伤大鼠可以学习位置反应，但只有在行为灵活性的要求最小化时，空间记忆才能表达。这些发现表明，在某些情况下，海马外结构足以构建空间的连贯非空间表示；然而，灵活的记忆表达基本上取决于海马的功能。
