Rotman Research Institute, Baycrest Centre, Toronto, Ontario, Canada.
Hippocampus. 2010 Dec;20(12):1350-65. doi: 10.1002/hipo.20721.
In previous work, we showed that adult rats that were reared socially for 3 months in a complex (village) environment retained allocentric spatial memory for that environment following hippocampal lesions (Winocur et al., (2005) Nat Neurosci 8:273–275). In the present series of experiments, we showed that 3 months of postoperative rearing did not confer the same benefits (Experiment 1), although hippocampal groups, with or without rearing experience, exhibited spatial learning after extensive training (Experiments 1 and 2). Experiment 3 showed that as little as 2 weeks of preoperative rearing in the village was sufficient to retain acquired spatial memories after hippocampal lesions. Probe testing revealed that, although rats with hippocampal lesions exhibited remarkably good memory for preoperatively learned locations in the village, they were impaired when changes in task demands required flexible use of existing spatial representations. In a direct test of flexibility (Experiment 4), preoperatively reared rats were administered a blockedroutes task in the original learning environment, in which on designated trials, a barrier was placed across one of the direct paths to the goal compartment. On encountering the barrier, control rats consistently selected the next most direct route, whereas rats with hippocampal lesions, despite using spatial strategies, made more errors and took longer to find the goal. The present results confirm that allocentric spatial memories can survive hippocampal damage but they are schematic in nature and less cohesive than those associated with cognitive maps in intact brains. As well, there was evidence that, although different processes are involved in their formation, the schematic memories that were acquired preoperatively and survived hippocampal lesions are essentially the same as those laboriously formed postoperatively after extensive training.
在之前的工作中，我们发现，在复杂环境（村庄）中社交饲养 3 个月的成年大鼠在海马损伤后仍保留对该环境的位置参照空间记忆（Winocur 等人，（2005）Nat Neurosci 8:273-275）。在本系列实验中，我们发现，3 个月的术后饲养并不能带来相同的益处（实验 1），尽管海马组，无论是否有饲养经验，在广泛训练后都表现出空间学习（实验 1 和 2）。实验 3 表明，在村庄中进行术前 2 周的饲养就足以保留海马损伤后的获得性空间记忆。探测测试表明，尽管海马损伤的大鼠对术前在村庄中学习的位置表现出极好的记忆，但当任务需求发生变化需要灵活使用现有空间表示时，它们的记忆就会受损。在对灵活性的直接测试（实验 4）中，术前饲养的大鼠在原始学习环境中接受了阻塞路线任务，在该任务中，在指定的试验中，在通往目标室的直接路径之一上放置了一个障碍物。遇到障碍物时，对照大鼠始终选择下一个最直接的路线，而海马损伤的大鼠尽管使用了空间策略，但犯了更多的错误，花费了更长的时间才找到目标。目前的结果证实，位置参照空间记忆可以在海马损伤后存活，但它们本质上是图式的，不如完整大脑中与认知地图相关的记忆紧密。此外，有证据表明，尽管形成它们的过程不同，但术前获得并在海马损伤后幸存的图式记忆与术后经过广泛训练后费力形成的记忆基本相同。
