Görisch Jutta, Schwarting Rainer K W
Experimental and Physiological Psychology, Philipps-University of Marburg, Gutenbergstr. 18, 35032 Marburg, Germany.
Neurobiol Learn Mem. 2006 Sep;86(2):175-87. doi: 10.1016/j.nlm.2006.02.004. Epub 2006 Apr 17.
Substantial work has shown that rats although identical in stock, sex, age, and housing conditions can differ considerably in terms of behavior and physiology. Such individual differences, which can be detected by specific behavioral screening tests, are rather stable, that is, they probably reflect a behavioral disposition or trait. Here, we asked whether and how such differences might affect performance in a task of spatial learning and memory, the radial maze. As in our previous work, we used the degree of rearing activity in a novel open field to assign male adult outbred Wistar rats into those with high versus low rearing activity (HRA/LRA rats). They were then tested in a plus-maze for possible differences in anxiety-related behavior. Finally, and most importantly, they were food deprived and underwent maze training using an 8-arm radial maze with four non-baited and four baited arms. One of these arms consistently contained a larger bait size than the other three. In the open field, HRA rats not only showed more rearing behavior, but also more locomotor activity than LRA rats. In the plus-maze, HRA rats again showed more locomotion, but did not differ in open arm time or percentage of open arm entries, that is, conventional measures of anxiety-related behavior. In the radial maze, HRA rats consistently needed less time to consume all pellets than LRA rats, which was due to faster locomotion on the arms and less time spent at the food pits (especially in baited arms) of HRA rats. During the initial days of training, they were also more efficient in obtaining all food pellets available. Furthermore, HRA rats visited more arms and made relatively less reference memory errors than LRA rats. This allowed them to forage food quickly, but was paralleled by more working memory errors than in LRA rats. In general, working memory errors were more frequent in the arm with the large bait size, but there were no indications that HRA and LRA rats responded differently dependent on reward size. Finally, LRA rats lost slightly more weight than HRA rats during the period of food deprivation. These results are discussed with respect to the role of cognitive and motivational mechanisms, which as subject-inherent factors can contribute substantially to inter-individual variability in the radial maze.
大量研究表明，尽管大鼠在种群、性别、年龄和饲养条件上相同，但在行为和生理方面可能存在显著差异。这种个体差异可通过特定的行为筛选测试检测到，且相当稳定，也就是说，它们可能反映了一种行为倾向或特质。在此，我们探讨了这些差异是否以及如何影响空间学习和记忆任务——放射状迷宫中的表现。与我们之前的研究一样，我们利用新奇开放场地中的直立活动程度，将雄性成年远交系Wistar大鼠分为高直立活动组和低直立活动组（高/低直立活动大鼠）。然后，在十字迷宫中测试它们在焦虑相关行为上可能存在的差异。最后，也是最重要的，使它们禁食，并使用一个有八条臂的放射状迷宫进行迷宫训练，其中四条臂不放置诱饵，四条臂放置诱饵。这些臂中的一条始终放置比其他三条更大的诱饵。在开放场地中，高直立活动大鼠不仅表现出更多的直立行为，而且比低直立活动大鼠有更多的运动活动。在十字迷宫中，高直立活动大鼠再次表现出更多的运动，但在开放臂停留时间或进入开放臂的百分比方面没有差异，即焦虑相关行为的传统测量指标。在放射状迷宫中，高直立活动大鼠始终比低直立活动大鼠消耗所有食丸所需的时间更少，这是因为高直立活动大鼠在臂上的运动速度更快，在食槽（尤其是放置诱饵的臂）停留的时间更少。在训练的最初几天，它们获取所有可用食丸的效率也更高。此外，高直立活动大鼠比低直立活动大鼠探索更多的臂，且产生的参考记忆错误相对较少。这使它们能够快速觅食，但同时也伴随着比低直立活动大鼠更多的工作记忆错误。一般来说，在放置大诱饵的臂上工作记忆错误更频繁，但没有迹象表明高直立活动大鼠和低直立活动大鼠对奖励大小的反应不同。最后，在禁食期间，低直立活动大鼠比高直立活动大鼠体重减轻得略多。我们将结合认知和动机机制的作用来讨论这些结果，这些作为个体内在因素，可在很大程度上导致放射状迷宫中个体间的变异性。
