Corbit Laura H, Ostlund Sean B, Balleine Bernard W
Department of Psychology University of California, Los Angeles, Los Angeles, California 90095, USA.
J Neurosci. 2002 Dec 15;22(24):10976-84. doi: 10.1523/JNEUROSCI.22-24-10976.2002.
Previous studies have shown that electrolytic lesions of the dorsal hippocampus render the instrumental performance of rats insensitive to selective degradation of the action-outcome contingency (Corbit and Balleine, 2000). In the present experiments, we sought to replicate this finding and to examine the effects of excitotoxic lesions. In the first three experiments, rats with either electrolytic or NMDA lesions of the dorsal hippocampus and sham-lesioned controls were trained to press two levers, each of which delivered a unique food outcome, before their sensitivity to outcome devaluation and degradation of the instrumental contingency was assessed. Although we were able to replicate our original finding that electrolytic lesions of the dorsal hippocampus render rats insensitive to selective degradation of the instrumental contingency, NMDA lesions of the dorsal hippocampus had no effect. Neither lesion had any detectable effect on sensitivity to outcome devaluation. In experiment 4, we assessed the possibility that the effect of the electrolytic lesion resulted from damage to fibers originating in the retrohippocampal region (including both entorhinal cortex and subiculum) by examining the impact of bilateral NMDA-induced lesions of the retrohippocampus on the same tasks. Importantly, this lesion produced a deficit similar to that observed after electrolytic hippocampal lesions. The final experiment used a disconnection procedure to assess more directly whether damage to efferents from the retrohippocampal region, rather than the dorsal hippocampus itself, can account for the observed deficit. The data from these tests suggest that the deficits observed previously after electrolytic hippocampal lesions were the result of damage to entorhinal efferents.
先前的研究表明，海马背侧的电解损伤会使大鼠的工具性表现对动作-结果关联性的选择性破坏不敏感（科尔比特和巴莱内，2000年）。在本实验中，我们试图重复这一发现并检验兴奋性毒性损伤的影响。在前三个实验中，对海马背侧进行电解损伤或NMDA损伤的大鼠以及假损伤对照组进行训练，使其按压两个杠杆，每个杠杆都会产生一种独特的食物结果，然后评估它们对结果贬值和工具性关联性破坏的敏感性。虽然我们能够重复最初的发现，即海马背侧的电解损伤会使大鼠对工具性关联性的选择性破坏不敏感，但海马背侧的NMDA损伤却没有效果。两种损伤对结果贬值的敏感性均未产生任何可检测到的影响。在实验4中，我们通过检查海马后区双侧NMDA诱导损伤对相同任务的影响，评估了电解损伤的影响是否源于对起源于海马后区（包括内嗅皮质和下托）的纤维的损伤这一可能性。重要的是，这种损伤产生的缺陷与海马电解损伤后观察到的缺陷相似。最后一个实验采用了一种切断程序，以更直接地评估海马后区传出纤维的损伤，而非海马背侧本身的损伤，是否能够解释观察到的缺陷。这些测试的数据表明，先前在海马电解损伤后观察到的缺陷是内嗅传出纤维损伤的结果。
