Relationship between the rewarding and aversive effects of morphine and amphetamine in individual subjects

Drugs of abuse have been reported to produce both rewarding and aversive effects, as evidenced by their ability to induce both conditioned place preferences (CPPs) and conditioned taste aversions (CTAs), respectively. Although several attempts have been made to assess the relationship between the rewarding and aversive effects of drugs in independent groups, it is unknown to what extent (if any) preferences and aversions are related in individual animals. The present study assessed this relationship by examining the ability of morphine (5 and 10 mg/kg) and amphetamine (3 and 5 mg/kg) to induce both place preferences and taste aversions in the same animal, using a concurrent CTA/CPP design. There was no consistent relationship between the ability of morphine or amphetamine at either dose to increase time spent on the drug-paired side and the ability to suppress consumption of the drug-paired taste. These results support the position that drugs of abuse have multiple stimulus effects, both rewarding and aversive, that condition place preferences and taste aversions independently.     

The preference of rats for free or response-produced food

Three experiments were performed to investigate the preference of rats for either free or response-produced food. Rats were trained to free feed in an operant chamber and then to leverpress for food. Subsequently, they were given a choice between continuing to leverpress for food on CRF, FR 2, and FR 10 schedules or free feeding. In three experiments the independent variable was the method of free-food presentation: A fixed free-food dish was used in the first experiment, a movable dish in the second, and a large flat dish in the third experiment. The results of the three experiments were very similar, with most of the rats showing a preference for the free food. This preference increased further when more than one response was required to produce a food pellet. These results contradict any conclusion that rats have a generalized tendency to prefer response-produced to free food but provide no answer to the question of why rats do on occasion respond for food in the presence of free food.     

Central-place foraging by rats on the radial maze: The effects of patch size,food distribution,and travel time

Rats foraged on a four-arm radial maze with one, two, three, and four food items (0.65.g pieces of cheese) placed on different arms (patches) of the maze. In two experiments, the hypothesis was tested that rats should carry food to the center of the maze more often when a patch contains one food item than when it contains multiple food items. Support for this prediction was found when the tendency to carry initial items encountered in patches was compared among the different sized patches. However, a further observation failed to support the hypothesis: Food carrying declined from first to last item encountered in multiple-item patches with clustered food items. Experiment 1 revealed that food carrying was reduced when travel time was increased by barriers placed at arm entrances. Both Experiments 1 and 2 indicated that the tendency for rats to carry food to the center of the radial maze increased as the distance of food encountered on an arm increased from the center. In both experiments, some rats dealt with the problem of multiple items by resorting to multiple-item loading, and some rats carried food items from the end of an arm to a point on the arm nearer the center for consumption.     

The effects of computer-assisted instruction on number combination skill in at-risk first graders

The purpose of this pilot study was to assess the potential for computer-assisted instruction (CAI) to enhance number combination skill among children with concurrent risk for math disability and reading disability. A secondary purpose was to examine the effects of CAI on spelling. At-risk students were assigned randomly to math or spelling CAI, which they received in 50 sessions over 18 weeks. Acquisition and transfer effects were assessed. The results indicated that math CAI was effective in promoting addition but not subtraction number combination skill and that transfer to arithmetic story problems did not occur. Spelling CAI effects were reliable on acquisition and transfer spelling measures, with small to moderate effect sizes on transfer to reading measures. These results provide the basis for additional work with larger samples.     

试析农村教育“为农服务”的负面影响

农村教育"为农服务"有一定的合理性,但过于重视其"为农服务"的功能,则会产生负面影响。主要表现为:影响教育"培养人"这一基本功能的发挥;加大城乡间的教育不公平,减少农村居民向上流动的机会;不利于农村劳动力的转移;夸大农村职业教育对发展农村教育及经济的作用。     

The effects of order of shock durations on helplessness in rats

Whereas rats exposed to a series of progressively decreasing shock durations show deficits in shuttle-escape performance 24 h later, the same number and intensity of shocks in the reverse (increasing) order of durations does not produce the “learned helplessness” effect (Balleine & Job, 1991). We conducted two experiments to establish the generality of this shock-duration order effect on other measures of distress and helplessness in rats. In Experiment 1, rats exposed to decreasing durations of inescapable shock showed reduced consumption of quinine-adulterated water (finickiness), whereas increasing durations produced no finickiness. By contrast, increasing shock durations produced greater conditioned fear to the shock context than did decreasing shock durations in Experiment 2. The differential effects of shock-duration order on finickiness and fear are explicated in terms of the specificity of fear conditioning during exposure to increasing versus decreasing series of shock duration orders.     

和为偶数的奇素数对的个数

和为偶数N的奇数对可分为三种情况,第一种是奇合数对(这里把1看做奇合数);第二种是1个是奇合数、1个是奇素数的奇数对;第三种是奇素数对.小于N的奇合数的大约个数可以根据奇合数所含的因数情况来求出,和为N的奇合数对的大约个数也可以根据奇合数对所含的因数情况来求出,小于N的奇合数除两两组成和为N的奇合数对外,其余只能与小于N的奇素数组成和为N的奇数对.求出前两种和为N的奇数对的大约个数,就能求出和为N的奇素数对的大约个数.     

Discrimination of the number of sequential events by rats

Ten rats were trained to press a right lever following two successive sounds and to press a left lever following four successive sounds. Three sound sequences were used in initial discrimination training, such that reliable classification could not be based on the duration of each sound, the interval between sounds, or the total duration of the sound sequence. Classification of seven novel sound sequences suggested that the animals were either using number or the sum of sound durations in a sequence as the relevant cue. When this total sound duration was put in conflict with number, rats classified by number. The conclusion was that rats can discriminate number, even when temporal cues are controlled.     

The effects of taste extinction on ingestional potentiation in weanling rats

Four experiments investigated taste potentiation in weanling rats. In Experiment 1, the animals that drank a conditioning compound of denatonium and saccharin consumed significantly less on the test than controls that drank only saccharin during conditioning. This enhanced saccharin aversion was decremented by postconditioning extinction to denatonium in Experiment 2, and no generalization of saccharin aversions to the denatonium was observed in Experiment 3. Extinction of either saccharin or denatonium aversions after compound conditioning was shown in Experiment 4 to result in substantial decrements in aversions to the compound. The relationship of these outcomes to a multiple-association account of potentiation and to the role of discrimination processes in ingestional learning is discussed.     

Effects of CSs for food and water upon rats barpressing for different magnitudes of food reinforcement

Forty-eight albino rats were first exposed to randomly intermixed, noncontingent presentations of one pellet, six pellets, and water. For each of three groups, a CS+ was paired with one of the reinforcers, while the other two reinforcers and a CS? were presented alone. Then half the subjects experienced a six-pellet reward and half experienced a one-pellet reward for leverpresses during a light S^D. Finally, on test trials, the CS+ or CS? was compounded with the light. Latencies on test trials indicated that responding for the one-pellet reward was significantly more disrupted by a CS+ for six pellets than by the CS+ for one pellet or the CS+ for water. Responding for the six-pellet reward was disrupted by the CS+ for one pellet somewhat more than by the CS+ for six pellets or water, but not significantly so. This pattern of results is partially consistent with an associative model of transfer and appears to contradict a motivational account of such effects.     

Serial position effects in social transmission of food preference

The serial position effect in Long-Evans rats was evaluated in two experiments. In Experiment 1, the effect in a group for which an interstimulus interval (ISI) was introduced between items in a list of demonstrators was compared with that in a group without an ISI. With an ISI, a recency effect was produced. In Experiment 2, a serial position effect group was compared with four groups in which either the distinctiveness or the context of the middle item was changed, relative to the items on either side of it. A von Restorff effect was produced when a rat from a different strain was used as a demonstrator in Position 2. The results for Experiment 1 are discussed in relation to interstimulus effects in monkeys and those for Experiment 2 with respect to changes in the physical properties of middle items.     

Maze patrolling by rats with and without food reward

The effects of food reward on rats’ behavior in radial and Dashiell tunnel mazes were examined in two experiments. In the first, with animals at ad-lib body weights, food reward reduced speed of movement at the food locations, but did not affect the patterns of movement in either maze. Exploratory efficiency in the Dashiell maze was unaffected by food reward, and spontaneous patrolling of the radial maze by the nonrewarded animals was comparable to the behavior, reported by others, of rats running for food reward on elevated eight-arm mazes. In the second experiment, with subjects maintained at 80% of ad-lib body weights, there was some evidence for “winstay” learning: food-rewarded rats in the Dashiell maze were relatively more active near the food locations than were the nonrewarded animals, and more rewarded than nonrewarded rats revisited all food locations in the radial maze. Nonetheless, exploratory efficiency in the Dashiell maze was unaffected by food reward, as was patrolling efficiency in the radial maze, which was again comparable to that of rats on elevated mazes. The similarity in behavior of rewarded and nonrewarded animals in these mazes implies that the major determinant of their behavior, whether or not food reward is provided, is a spontaneous tendency to avoid places recently visited.     

Acquisition of barpressing in rats following experience with response-independent food

In a three-group experiment, one group of rats (response-contingent) learned to contact a food cup for Noyes food pellets delivered according to a fixed-ratio schedule of reinforcement. Subjects in another group received a response-independent pellet each time its yoked counterpart earned one. A third (control) group received the same amount of food as the other two groups each day, but the pellets were delivered in mass. Following this training, the rats were placed in a novel experimental chamber in which all responses on a bar were reinforced with the presentation of food pellets. The results showed the response-independent animals to be slower in acquiring the barpress response than the naive control subjects, and the response-contingent subjects to be the fastest.     

Social transmission of food preferences among norway rats by marking of food sites and by gustatory contact

Three experiments were conducted to investigate the social learning and transmission of food preferences by excretory marking among adult male Norway rats. The experiments extend our earlier findings that rats prefer to eat from a food bowl marked by the excretory deposits of conspecifics and that this mechanism can result in the communication and social learning of food preferences (Laland & Plotkin, 1991). Here we investigate whether a tradition of food and food site preferences can become established by these means. Experiment 1 established that the residual cues deposited by rats lose their powers of communication as “markers” of food sites over a 72-h period. Experiment 2 showed that while a socially enhanced preference for one flavored diet could be transmitted from one animal to the next along a chain, it was unstable for an alternative diet. This suggests that social transmission may be more stable when it reinforces a prior preference than when it conflicts with one. In Experiment 3, the stability of socially transmitted food preferences was bolstered by the addition of a second process for the communication of diet preferences-namely, gustatory cues on the demonstrator’s breath. This finding suggests that when a socially transmitted trait is mediated by more than one process, the processes may interact, and the diffusion is likely to be more stable.     

Discrimination of geons by pigeons: The effects of variations in surface depiction

We explored how changes in the depiction of the surface features of a simple volume (a geon) affected the pigeon’s recognition performance. Pigeons were trained to make a different keypeck response to each of four computer-rendered single-geon objects. In Experiment 1, the pigeons were tested with images of the original stimuli in which the light source was shifted from its original position, as well as with silhouettes and line drawings of these objects. All three types of stimulus variations resulted in marked drops in performance: above chance for silhouettes and light-change stimuli, but at chance for line drawings. In Experiment 2, the pigeons were tested with images of the original stimuli in which the contrast levels were either increased or decreased. These transformations resulted in very small drops in performance (except for the complete absence of contrast-a silhouette). These results indicated that the pigeons attended to the shape of the outside contour of an object and to the relative brightness of an object’s surface contours.     

Extinction of rats’ barpressing in the presence of free food

In two experiments, hungry rats received four extinction sessions in the presence of free food. When the free food was removed for eight subsequent extinction sessions, the animals made significantly fewer responses than did control groups which received no intervening sessions. The results are contrary to those of Enkema et al (1972). From the results of additional groups of rats which received four intervening sessions of free food only, empty chamber, or time in home cage, it was concluded that the presence of free food caused the diminution in extinction responding.     

表面和界面效应对铁电薄膜极化分布的影响

运用铁电的Thomas和Landau理论,研究了外延铁电膜中极化分布受表面和界面的影响.结果表明:由于膜中存在表面和界面效应的竞争,对于超薄膜,表面效应占优,界面处极化强度(极化)变小;反之对于厚膜,界面效应占优,界面处极化变大.外推长度δ大于零、正比于膜中电偶极子间的关联长度η,δ/η与偶极子倔强系数的大小有关、与温度无关.     

The effects of social isolation on two shock-induced aggressive responses in rats

This experiment investigated the effects of social isolation during development and during adulthood on the topography of the shock-induced aggressive behavior of rats. Rats isolated during development from weaning to adulthood displayed more shock-induced biting than rats housed in groups during that period. Isolation during development did not affect the frequency of the upright boxing behavior, but isolation during adulthood reduced the frequency of the boxing response regardless of rearing conditions during development.