Whishaw I Q, Jarrard L E
Department of Psychology, University of Lethbridge, Alberta, Canada.
Hippocampus. 1995;5(6):595-604. doi: 10.1002/hipo.450050610.
Damage to either the fimbria-fornix or to the hippocampus can produce a deficit in spatial behavior and change in locomotor activity but the extent to which the two kinds of damage are comparable is not known. Here we contrasted the effects of cathodal sections of the fimbria-fornix with ibotenic acid lesions of the cells of the hippocampus (Ammon's horn and the dentate gyrus) on place learning in a swimming pool and on circadian activity. Rats in both ablation groups were impaired relative to control rats in learning a single place response but they did acquire the response as measured by swim latencies, errors, and by enhanced searching on probe trials. They were also more active than the control group on the test of activity. Nevertheless, the fimbria-fornix group was initially more impaired on learning and was more active than the hippocampal group. Analysis of the strategies used in learning indicated that the lesion groups were very similar to each other but different from the control group especially in that at asymptotic performance, rats in both lesion groups made rather tight loops as they swam toward the platform. This strategy likely contributed to the greater proportion of time they spent swimming in the correct quadrant on the subsequent probe trial. These findings confirm that rats with fimbria-fornix or hippocampal damage display impairments in place learning and are hyperactive but also show that there are lesion differences. The results are discussed with respect to the relative effectiveness of the lesions and the possibility that fibers in the fimbria-fornix may mediate some functions that are not attributable to the hippocampus.
穹窿 - 海马伞或海马体受损均可导致空间行为缺陷和运动活动改变，但两种损伤的可比程度尚不清楚。在此，我们对比了穹窿 - 海马伞阴极切断术与海马体（海马角和齿状回）细胞的鹅膏蕈氨酸损伤对在游泳池中位置学习和昼夜活动的影响。相对于对照大鼠，两个切除组的大鼠在学习单一位置反应时均受损，但通过游泳潜伏期、错误次数以及在探测试验中增强的搜索行为来衡量，它们确实学会了该反应。在活动测试中，它们也比对照组更活跃。然而，穹窿 - 海马伞组在学习上最初受损更严重，且比海马体组更活跃。对学习中使用的策略进行分析表明，损伤组彼此非常相似，但与对照组不同，特别是在渐近表现时，两个损伤组的大鼠在游向平台时形成相当紧密的圈。这种策略可能导致它们在随后的探测试验中在正确象限游泳的时间比例更大。这些发现证实，穹窿 - 海马伞或海马体损伤的大鼠在位置学习中表现出损伤且活动亢进，但也表明存在损伤差异。我们根据损伤的相对有效性以及穹窿 - 海马伞中的纤维可能介导一些不归因于海马体的功能的可能性来讨论这些结果。
