Abstract：
Damage to the hippocampus produces profound retrograde amnesia, but odour and object discrimination memories can be spared in the retrograde direction. Prior lesion studies testing retrograde amnesia for object/odour discriminations are problematic due to sparing of large parts of the hippocampus, which may support memory recall, and/or the presence of uncontrolled, distinctive odours that may support object discrimination. To address these issues, we used a simple object discrimination test to assess memory in male rats. Two visually distinct objects, paired with distinct odour cues, were presented. One object was associated with a reward. Following training, neurotoxic hippocampal lesions were made using N-methyl-D-aspartate (NMDA). The rats were then tested on the preoperatively learned object discrimination problem, with and without the availability of odour or visual cues during testing. The rats were also postoperatively trained on a new object discrimination problem. Lesion sizes ranged from 67% to 97% of the hippocampus (average of 87%). On the preoperatively learned discrimination problem, the rats with hippocampal lesions showed preserved object discrimination memory when tested in the dark (i.e., without visual cues) but not when the explicit odour cues were removed from the objects. Hippocampal lesions increased the number of trials required to reach criterion but did not prevent rats from solving the postoperatively learned discrimination problem. Our results support the idea that long-term memories for odours, unlike recall of visual properties of objects, do not depend on the hippocampus in rats, consistent with previous observations that hippocampal damage does not cause retrograde amnesia for odour memories.
摘要：
海马体的损伤会导致严重的逆行性健忘症，但是气味和物体辨别记忆可以在逆行方向上幸免。先前的病变研究测试逆行性健忘症的对象/气味区分是有问题的，因为海马体的大部分保留，可以支持记忆回忆，和/或不受控制的存在，可能支持对象歧视的独特气味。为了解决这些问题,我们用一个简单的对象辨别测试来评估雄性大鼠的记忆力。两个视觉上不同的物体，搭配明显的气味提示，被介绍了。一个物体与奖励有关。培训后,使用N-甲基-D-天冬氨酸（NMDA）制作神经毒性海马病变。然后对大鼠进行术前学习对象辨别问题的测试，在测试过程中，有或没有气味或视觉线索的可用性。术后还对大鼠进行了新的对象辨别问题的训练。病变大小范围为海马的67%至97%(平均87%)。关于术前学习歧视问题，在黑暗中测试时，具有海马病变的大鼠表现出保留的物体辨别记忆(即，没有视觉提示），但当从对象中删除明确的气味提示时，则没有。海马病变增加了达到标准所需的试验数量，但并未阻止大鼠解决术后学习的歧视问题。我们的结果支持了对气味的长期记忆，与回忆对象的视觉属性不同，不依赖于大鼠的海马，与先前的观察结果一致，海马损伤不会导致气味记忆的逆行性健忘症。
