Time-place learning in the eight-arm radial maze

Rats (n=4) searched for food on an eight-arm radial maze. Daily 56-min sessions were divided into eight 7-min time zones, during each of which a different location provided food; locations were randomized across subjects before training. The rats obtained multiple pellets within each time zone by leaving and returning to the correct location. Evidence that the rats had knowledge about the temporal and spatial features of the task includes the following. The rats anticipated locations before they became active and anticipated the end of the currently active locations. The rats discriminated currently active locations from earlier and forthcoming active locations in the absence of food transition cues. After the rats had left the previously active location, they visited the next correct location more often than would be expected by chance in the absence of food transition cues. The rats used handling or opening doors as a cue to visit the first location and timed successive 7-min intervals to get to subsequent locations.     

Spatial pattern learning in the radial arm maze

Rats experienced a spatial pattern of baited and unbaited arms in an eight-arm radial maze. The spatial pattern remained constant over trials, but the spatial locations that were baited varied unpredictably. Although there was no evidence of control by the spatial pattern during free choice training trials, the rats’ ability to locate baited arms in forced choice test trials was superior to that of animals in a control condition for which maze arms were not baited in a consistent spatial pattern. This is consistent with the results of experiments showing that spatial choices by rats in a pole box maze are controlled by abstract spatial patterns.     

Transfer of visual and haptic maze learning in rats

Cross-modal transfer of learning between black/white and rough/smooth discrimination tasks was studied in a two-choice maze procedure in which the stimuli for both discriminations were located on the floor of the maze. Rats were trained initially with cues of one modality and then given transfer training with cues of the second modality. The amount of transfer produced by two criteria of learning, 9 correct responses in 10 trials and 18 correct responses in 20 trials, was also studied. Bidirectional cross-modal transfer of learning was demonstrated more clearly with the more stringent learning criteria. These positive transfer effects appeared primarily to be the result of general transfer processes.     

Multiple-pattern learning by rats on an eight-arm radial maze

Rats were trained over a number of sessions on an eight-arm radial maze with eight trials on each session. Each of four arms on the maze contained a different pattern formed by sequences of reward (two pellets) or nonreward (no pellets) over successive trials within sessions. The patterns were single alternation, double alternation, and two patterns in which four rewards or four nonrewards were preceded and followed by two nonrewards or two rewards, respectively. The other four arms on the maze served as control arms and always contained one pellet. It was found that rats tracked all of these patterns when they were required to climb over barriers to enter and leave arms. However, rats showed no ability to extrapolate patterns beyond the training trials. These findings, and a further analysis of arm-choice stereotypy, led to the conclusion that rats tracked by using a trial-number strategy.     

Partial reinforcement effects on learning and extinction of place preferences in the water maze

In two experiments, two groups of rats were trained in a navigation task according to either a continuous or a partial schedule of reinforcement. In Experiment 1, animals that were given continuous reinforcement extinguished the spatial response of approaching the goal location more readily than animals given partial reinforcement—a partial reinforcement extinction effect. In Experiment 2, after partially or continuously reinforced training, animals were trained in a new task that made use of the same reinforcer according to a continuous reinforcement schedule. Animals initially given partial reinforcement performed better in the novel task than did rats initially given continuous reinforcement. These results replicate, in the spatial domain, well-known partial reinforcement phenomena typically observed in the context of Pavlovian and instrumental conditioning, suggesting that similar principles govern spatial and associative learning. The results reported support the notion that salience modulation processes play a key role in determining partial reinforcement effects.     

A “random-walk” simulation model of multiple-pattern learning in a radial-arm maze

Wathen and Roberts (1994) reported rather surprising results of a radial maze study that on any interpretation requires postulation of previously unsuspected high-level cognitive processes in rats. In each of four arms of the eight-arm radial maze, a different serial pattern unfolded over trials; for example, in one of the arms reward and nonreward alternated over successive trials. On each trial, rats came to track successfully four different patterns simultaneously. The authors suggested that rats tracked the pattern by using some form of trial-number strategy; that is, the trial number indicated which arms contained the better rewards. This strategy could involve a hypothesis, considered unlikely by some, that rats are capable of keeping track of as many as eight successive events—as, for example, by counting. A simulation model that embodies a specific form of the trial-number hypothesis is described here, and the results of the simulation correlate remarkably well with the observed data. In addition, the model makes four separate predictions that are supported by Wathen and Roberts’s data and that seem beyond the scope of other available theories.     

Reversal of spatial discrimination learning in a water maze by previously undernourished rats

The development of the hippocampus in rats may be vulnerable to undernutrition during the fetal and suckling periods. Hence the behavioral effects of early growth restriction may resemble those of hippocampal lesions. This suggestion was investigated by testing previously undernourished rats for reversal learning, an ability badly affected in hippocampectomized rats. Developing rats were undernourished by feeding their mothers a restricted quantity of a good quality diet during pregnancy and lactation. All rats were fed ad lib from weaning. Reversal of spatial discrimination learning was tested in adult animals using a water T-maze. Previously undernourished rats learned the initial spatial discrimination more quickly than controls. However, there was no effect of early treatment on serial reversal learning in Experiment I or on performance of a single reversal after prolonged initial training in Experiment II.     

Testing optimal foraging theory on the radial maze: The role of learning in patch sampling

A four-arm radial maze containing 10 feeders in each arm (patch) was used to study patch sampling in rats. In each of three experiments, rats foraged for 30 sessions. On each session, two randomly chosen patches were baited with food and the remaining two patches were empty. In Experiment 1, the number of baited feeders in baited patches (6) was varied from 1–10 over five groups of subjects. Mean visits to empty patches was an inverse function of 6, as predicted by an optimal foraging model. In Experiments 2 and 3, rats’ ability to discriminate between baited and empty patches was examined when food in baited patches was placed in fixed locations, either in clumps (Experiment 2) or distributed throughout the patch (Experiment 3). Rats in fixed-food-location conditions reliably visited fewer feeders in empty patches than did rats in randomly changing control groups. Examination of within-patch foraging patterns indicated that rats in fixed-food-location groups selectively sampled potentially baited locations and abandoned the patch if food was not found. It is suggested that processes of patch discrimination were responsible for these effects.     

Spatial configuration and list learning of proximally cued arms by rats in the enclosed four-arm radial maze

In an enclosed four-arm radial maze, after sampling three experimenter-selected baited arms (thestudy segment) and following rotation of the maze, rats had to find the fourth baited arm among all four unblocked arms (test segment). The rats learned this task with two sets of arm cues, objects at arms’ entrances and full arm inserts, each maintained in a fixed configuration. When we changed the configuration of one set of arms to itsmirror image and that of the other set to a moremixed variation by switching opposite and adjacent cued arms, the rats’ accuracy was similarly disrupted (Experiment 1). In Experiment 2, the same rats rapidly recovered their high search accuracy on four new configurations recombined from pairs of adjacent arms and pairs of opposite cued arms from the previous final two configurations. Their test segment search accuracy, however, was again disrupted when these configurations were varied either only over trials’ study segments or only over trials’ test segments. In Experiment 3, however, these rats attained accuracy as high on two sets of cued arms with constantly changing configurations as on two sets with constant configurations. Thus, the rats were able to separately represent four different spatially stable configurations, and then they could learn to represent two of these configurations as lists of spatially irrelevant items. We discuss these findings in terms of association theory and parallel map theory (Jacobs & Schenk, 2003).     

迷失的寻找之旅——从“丢失—寻找”主题解读凡一平都市小说

从＂丢失—寻找＂主题探索凡一平都市小说的叙事结构,发现：其表层结构包括了＂丢失—寻找—回归初始＂和＂丢失—寻找—彻底失去＂两种叙事模式;在深层结构中,凡一平则通过小说人物的＂寻找＂来实现自己的寻找,即他通过人物的选择来演绎都市生存中人的异化,通过人物的人性流失来探索人异化的深层原因。     

谈《佚存曲谱》

乾隆以后,记载昆曲在扬州活动的史料极少,宝应郁念纯先生旧藏,靖江徐沁君教授和苏州王正来先生校阅整理的《佚存曲谱》初集两卷,在昆曲界引起了很大反响,但至今未能引起学术界的注意,本从演出剧本和音乐唱腔的角度,说明《佚存曲谱》即填补了乾隆以后扬州昆腔流布的空白,又为扬州在历史上曾经存在过“扬昆”,提供了有力的佐证。     

浅析《我逝去的青春》中的修辞

亨利·沃兹沃斯·朗费罗是十九世纪美国最伟大的浪漫主义诗人,其诗作质朴单纯,韵律优美,看似平凡却蕴含人生哲理。《我逝去的青春》抒发了诗人对已逝青春的悠悠思念和淡淡哀愁。从修辞手法的角度对该诗进行分析,认为隐喻、倒装、典故及重复等修辞手法的巧妙运用,有力烘托了整首诗的主题。     

逝去的爱

My days are growing long My nights are growing shortMy life is growing strongMy death is growing closeMaybe I’ll forget Maybe I’ll remember Maybe I’ll loveMaybe I’ll hateI thought I knewI thought I forgotI thought I would Lose my memory of you逝去的爱     

丢手提包

一个女人丢了手提包,有一个诚实的小孩捡到后交还给了她。 她看了看钱包,说：“嗯,这么有趣,我丢的时候里面是一张20美元,现在成了20张一美元。”     

《迷失在开心馆中》宗教思想探微

约翰·巴思在短篇小说集《迷失在开心馆中》以模仿—颠覆的对立方式展示出其复杂的宗教观。作家在模仿《圣经·主祷文》的体式后对其进行彻底颠覆,模仿上帝创世继而又怀疑、颠覆上帝的存在。该部小说集中展现出巴思宗教怀疑主义、多神论的复杂宗教观,生动折射出20世纪60、70年代美国思想动荡、信仰危机的社会状况。     

Lost Diary

<正>I learned the text To Build a Fire a week ago,the protagonisthas a husky,and that made me feel really sad.Two years ago I had a husky too.I still miss her so much,she is a little star in my life,glittering,but distant.She was a pretty girl,lively and cute,like a ball of fur.Her eyes are black,like obsidians,fascinating.That’s the most beautiful part in her body.For some reasons,I had to transfer to