Clark Robert E, Broadbent Nicola J, Squire Larry R
Veterans Affairs Medical Center, San Diego, California, USA.
Hippocampus. 2005;15(2):260-72. doi: 10.1002/hipo.20056.
Damage to the hippocampus typically produces temporally graded retrograde amnesia, whereby memories acquired recently are impaired more than memories acquired remotely. This phenomenon has been demonstrated repeatedly in a variety of species and tasks. It has also figured prominently in theoretical treatments of memory and hippocampal function. Yet temporally graded retrograde amnesia has not been demonstrated following hippocampal damage in spatial tasks like the water maze. We have assessed recent and remote spatial memory following hippocampal lesions in three different tests of spatial memory: (1) the standard water maze; (2) the Oasis maze, a dry-land version of the water maze; and (3) the annular water maze, where training and testing occur within a circular corridor. Training protocols were developed for each task such that retention of spatial memory could be expressed after very long retention intervals. In addition, retention in each task was assessed with single probe trials so that the assessment of remote memory did not depend on the ability to relearn across multiple trials. The findings were consistent across the three tasks. In the standard water maze (Experiment 1), spatial memory was impaired after training-surgery intervals of 1 day, 8 weeks, or 14 weeks. Similarly, in the Oasis maze (Experiment 2), spatial memory was impaired after training-surgery intervals of 1 day and 9 weeks. Finally, in the annular water maze (Experiment 3), spatial memory was impaired after training-surgery intervals of 9 weeks and 14 weeks. Dorsal hippocampal lesions impaired performance to the same extent as complete lesions. The impairment in remote spatial memory could reflect disruption of previously acquired spatial information. Alternatively, it is possible that in these tasks hippocampal lesions might produce an impairment in performance that prevents the expression of an otherwise intact spatial memory.
海马体受损通常会导致时间梯度性逆行性遗忘，即近期获得的记忆比远期获得的记忆受损更严重。这一现象已在多种物种和任务中得到反复证实。它在记忆和海马体功能的理论探讨中也占据显著地位。然而，在水迷宫等空间任务中，海马体受损后尚未证实存在时间梯度性逆行性遗忘。我们在三种不同的空间记忆测试中评估了海马体损伤后的近期和远期空间记忆：（1）标准水迷宫；（2）绿洲迷宫，水迷宫的陆地版本；（3）环形水迷宫，训练和测试在圆形通道内进行。针对每个任务制定了训练方案，以便在很长的保持间隔后仍能表现出空间记忆的保持情况。此外，每个任务的保持情况通过单次探针试验进行评估，这样对远期记忆的评估不依赖于多次试验后重新学习的能力。三项任务的结果一致。在标准水迷宫（实验1）中，训练 - 手术间隔1天、8周或14周后，空间记忆受损。同样，在绿洲迷宫（实验2）中，训练 - 手术间隔1天和9周后，空间记忆受损。最后，在环形水迷宫（实验3）中，训练 - 手术间隔9周和14周后，空间记忆受损。背侧海马体损伤与完全损伤对行为表现的损害程度相同。远期空间记忆受损可能反映了先前获得的空间信息的破坏。或者，在这些任务中，海马体损伤可能会导致行为表现受损，从而妨碍原本完整的空间记忆的表达。
