Gorny Joanna H, Gorny Bogdan, Wallace Douglas G, Whishaw Ian Q
Canadian Centre for Behavioural Neuroscience, University of Lethbridge, Lethbridge, Alberta T1K 4N6, Canada.
Learn Mem. 2002 Nov-Dec;9(6):387-94. doi: 10.1101/lm.53002.
Exploration is the primary way in which rodents gather information about their spatial surroundings. Thus, spatial theories propose that damage to the hippocampus, a structure thought to play a fundamental role in spatial behavior, should disrupt exploration. Exploration in rats is organized. The animals create home bases that are central to exploratory excursions and returns, and hippocampal formation damage alters the organization of exploration by disrupting returns. Mice do not appear to readily establish home bases in novel environments, thus, for this species, it is more difficult to establish the contribution of the hippocampus to exploration. The purpose of the present study was threefold: develop a task in which mice center their exploration from a home base, determine whether the exploratory behavior is organized, and evaluate the role of fimbria-fornix lesions on exploration. Mice were given a novel exploratory task in which their nesting material was placed on a large circular table. Video records of control and fimbria-fornix mice were made in both light and dark (infrared light) conditions. Exploration patterns (outward trips, stops, and homeward trips) were reconstructed from the video records. Control mice centered their activity on their bedding, from which they made circuitous outward trips marked by many stops, and periodic direct returns. The bedding-centered behavior and outward trips of the fimbria-fornix mice were similar to those of the control mice, but significantly fewer direct return trips occurred. The direct homeward trips observed under light and dark conditions were consistent with a dead-reckoning strategy, in which an animal computes its present position and homeward trajectory from self-movement cues generated on the outward trip. Because the fimbria-fornix lesions disrupted the homeward component of exploratory trips, we conclude that the fimbria-fornix may contribute to dead reckoning in mice. The results also show that the home-bedding methodology facilitates the establishment of a home base by mice, thus providing a useful methodology for studies with mice.
探索是啮齿动物收集有关其空间环境信息的主要方式。因此，空间理论提出，海马体（一种被认为在空间行为中起基本作用的结构）受损应会扰乱探索行为。大鼠的探索行为是有组织的。动物会建立起作为探索性外出和返回核心的家域，而海马结构受损会通过扰乱返回行为来改变探索行为的组织方式。小鼠在新环境中似乎不容易建立家域，因此，对于这个物种来说，确定海马体对探索行为的贡献更加困难。本研究的目的有三个：开发一种让小鼠从家域出发进行探索的任务，确定探索行为是否有组织，并评估穹窿海马伞损伤对探索行为的作用。给小鼠一项新的探索任务，将它们的筑巢材料放在一个大圆形桌子上。在光照和黑暗（红外光）条件下对对照组和穹窿海马伞损伤小鼠进行视频记录。从视频记录中重建探索模式（外出行程、停留和返回行程）。对照小鼠将其活动集中在它们的垫料上，从垫料出发进行迂回的外出行程，行程中有许多停留点，还有定期的直接返回。穹窿海马伞损伤小鼠以垫料为中心的行为和外出行程与对照小鼠相似，但直接返回行程明显减少。在光照和黑暗条件下观察到的直接回家行程与一种航位推算策略一致，即动物根据外出行程中产生的自身运动线索计算其当前位置和回家轨迹。由于穹窿海马伞损伤扰乱了探索行程的回家部分，我们得出结论，穹窿海马伞可能有助于小鼠的航位推算。结果还表明，家域垫料方法有助于小鼠建立家域，从而为小鼠研究提供了一种有用的方法。
