Successive negative contrast in the consummatory responding of didelphid marsupials

In a consummatory experiment patterned after previous work with rats and goldfish, successive negative incentive contrast was sought in didelphid marsupials of two species (Lutreolina crassicaudata andDidelphis albiventris). Half of the subjects of each species were trained from the outset with a 32% sucrose solution and shifted occasionally to a 4% sucrose solution; the rest, which served as controls, were trained only with the 4% solution. The positive results obtained (less response to the 4% solution in the shifted subjects than in the controls) fit the hypothesis, based on comparative work with descendants of older vertebrate lines, that the mechanism of successive negative incentive contrast evolved in a common reptilian ancestor of birds and mammals.     

Proactive interference of open field on consummatory successive negative contrast

Reactivity to a reward is affected by prior experience with the different reinforcer values of that reward, a phenomenon known as incentive relativity, which can be studied using the consummatory succesive negative contrast (cSNC) paradigm, in which the performance of animals that receive a 4 % sucrose solution after trials on which they were exposed to 32 % sucrose is compared with that of subjects that always receive the 4 % sucrose solution. The exploration of a novel open field can enhance or block the acquisition of associative and nonassociative memories. The effect of open field on cSNC has not yet been explored. The main result of the present study was that open-field exposure significantly modified the expression of cSNC. Exposure to an open field 1 h but not immediately before the downshift interfered with the expression of cSNC. These animals drank more of the downshifted reward than did controls that were not exposed to the apparatus, and this behavior persisted for up to three recovery trials. This phenomenon was observed even when the animals were given a more protracted preshift phase and when the discrepancy between the preshift and shift incentive values of sucrose were increased. An open field also interfered with incentive downshift when open-field exposure occurred 6 h before the downshift, and repeated exposure to the apparatus did not deteriorate this effect. The present study adds to a growing body of literature that indicates that open-field exploration can interfere with memory formation.     

Repeated successive contrast in consummatory behavior with repeated shifts in sucrose concentration

Contrast in consummatory behavior was investigated following repeated shifts from 32% to 4% sucrose. In Experiment 1, contrast in licking and in open-field measures of activity occurred following the second and third downshifts. In Experiments 2a and 2b, equivalent contrast effects occurred following the first and second downshifts in sucrose. In Experiment 3, negative contrast remained unabated following nine downshifts in animals shifted between 32% and 4% sucrose on alternate days. Similar results were found for five downshifts in animals shifted every 2 days. In both of these latter conditions, positive contrast occurred over the first few shifts and was then lost as the 32% control group reached asymptote. These data show that repeated negative contrast effects in consummatory behavior are robust and enduring and occur under several different sets of experimental parameters. The results are discussed in terms of reinforcement level and emotional interpretations of contrast effects, and the possibility was suggested that the causal mechanism of contrast changes with repeated shifts.     

Partial reward,the negative contrast effect,and incentive averaging

A total of 169 rats, distributed across six experiments, received training in a straight runway with a 5-min intertrial interval. A variety of shifts in reward schedules, to and from partial reward, were employed to assess the effects of partial reward on the successive negative contrast effect. The results were seen as supportive of an incentive averaging approach to partial reinforcement.     

Positive and negative contrast effects obtained following shifts in liquid sucrose reward in thirsty rats

In a repeated shifts experiment four independent groups of thirsty rats received the following treatments: LSLS, LLLS, SSLS, and SSSS, with each letter denoting the magnitude (large or small) of sucrose reward received in each of the four phases of the experiment. While no negative contrast effect (NCE) was obtained in Phase 2, a very reliable positive contrast effect (PCE) was found in Phase 3. Moreover, a significant NCE was obtained in Phase 4. The results were explained in terms of the relative rather than absolute effects of reinforcement.     

Evidence for the interchangeability of an avoidance behavior and a negative occasion setter

Recent research on avoidance behavior provided evidence that such behavior can function as a negative occasion setter. We tested this hypothesis further by investigating whether the modulatory function of a stimulus occasion setter transfers selectively to a relation previously modulated by an avoidance behavior, and whether the modulatory function of an avoidance behavior transfers selectively to a relation previously modulated by a stimulus occasion setter. The three experiments reported in this article provided evidence to support this hypothesis. Furthermore, the results of Experiment 1 suggested that the presence of counterconditioning trials is not a necessary condition for an avoidance behavior to function as a negative occasion setter. All three reported experiments support the occasionsetting account of avoidance behavior.     

磁场对不同半导体异质结构负施主中心的影响

讨论了两种半导体异质结构中负施主中心（D）能量随磁场的变化情况,计算中利用变分的方法,分析磁场中的电子结构,得到描述电子内外轨道参量随磁场的变化情况,计算此异质结构中负施主角动量L 1三重态的本征能量和束缚能,发现L 1三重态在外加磁场0.053时实现了由非束缚态到束缚态的转变。同时计及电子与界面声子的相互作用,数值计算并对比了界面声子对CdSe（ZnSe）和GaAs（GaP）半导体异质界面上D的束缚能的影响。     

Effect of experience with a preferred food on consummatory responding for a less preferred food in goldfish

In two experiments with goldfish patterned after work with rats, consummatory responding for a less preferred food (adulterated with quinine) was measured in subjects that did or did not have previous experience of a preferred (unadulterated) food. The result in each case was not the negative contrast found in rats, but the opposite—more responding in subjects with experience of both foods. The experiments are in accord with a variety of others that have failed to show control of performance by remembered reward in goldfish.     

Evidence for a shift in the choice criterion of rats in a 12-arm radial maze

Rats were trained in a standard 12-arm radial maze task. Following training, each trial consisted of a sequence of 2, 4, 6, 8, or 10 choices, followed by a 15-min delay, which then was followed by a choice between a single arm and a response manipulandum mounted in the center of the maze. An arm visit was reinforced if the arm had not been visited prior to the delay, whereas a manipulandum response was reinforced if the arm had been visited. It was found that rats are relatively more likely to reject arms by responding to the manipulandum following a delay occurring late in the choice sequence. This indicates that the choice criterion used by rats in the radial maze becomes more strict as the choice sequence progresses. Such a process provides an alternative explanation for some of the data recently reported by Cook, Brown, and Riley (1985).     

Correlation of corticosterone elevation and negative contrast varies as a function of postshift day

In three experiments, rats shifted from 32% to 4% sucrose consumed less of the 4% sucrose than did rats that had received only the 4% solution. Experiment 1 showed that this negative contrast effect was not accompanied by a corticosterone elevation on the first day subsequent to the shift. Experiments 2 and 2a showed that corticosterone levels were substantially elevated on the 2nd postshift day and that there was a tendency for degree of elevation in corticosterone to be related to degree of lick suppression. These results are discussed in terms of other data suggesting that anxiolytic drugs and disinhibitory stimuli are more effective in alleviating contrast on the 2nd postshift day than on the 1st postshift day. It is suggested that, in the present paradigm, reaction to stimulus change may be the primary determinant of contrast on the 1st postshift day, but emotional processes related to reward loss and/or conflict develop by the 2nd postshift day.     

Extinction of a taste aversion in the absence of the consummatory response

Rats were initially conditioned to avoid saccharin presented orally and were then given 40 intravenous injections of saccharin or saline. Those injected with saccharin showed more rapid extinction of the aversion to saccharin presented orally. Results are related to studies of shock avoidance using curarized subjects.     

不良广告组合的负面效应分析

针对当前企业经营理念存在的误差,从广告主题、文案、画面等设计不当而产生的不良效应入手,通过对不良表现形式的研讨.提出了企业经营必须要以诚信原则为指导,只有真实可信、组合得当、设计合理的广告促销形式,才能达到预期的营销策略效果,取得理想的经济效益.     

一个用于体外评价超声造影剂显影效果的系统（英文）

构建并评价了一个用于体外研究超声造影剂显影效果的系统,该系统包括一套数字化B型超声诊断仪Belson3000A、仿组织超声体模和用于图像量化分析的软件.制备了具有不同反射强度的仿组织超声体模,通过对这些体模材料超声成像,研究了B超系统的线性范围、参数设置和系统的重复性等.超声成像设置为：输出声功率为4.8 ～12.3mW,探头的中心频率为3.5MHz,总增益为50dB.利用该系统,对自制备的表面活性剂微气泡和一种商用造影剂进行了显影成像.结果表明超声图像的灰度值随声功率的增加而增大,强反射特性的超声体模成像时,这种增加趋势更明显.该系统适合用于体外评价超声造影剂的显影效果,为体外表征超声微气泡造影剂的显影能力提供了一种简单、有效、实时的评价方法.     

Behavioral contrast in pigeons and rats: A comparative analysis

The effects of reinforcement rate on behavioral contrast were examined in pigeons and rats. Each species was exposed to a series of 12 multiple variable-interval schedules, divided into four 3-schedule series. Each series consisted of a standard contrast manipulation, and baseline schedules provided a different rate of reinforcement in each of the series. The functions relating reinforcement rate to the magnitude of contrast were different across species. Rats showed a U-shaped function, with reliable contrast occurring only at high reinforcement rates. Pigeons showed an inverted U-shaped function, with contrast occurring on all schedules except the schedule providing the lowest rate of reinforcement. Pigeons discriminated between schedule components better than rats did, although differences in discrimination were probably not responsible for the differences in contrast. The results suggest that behavioral contrast in rats may be a different phenomenon from behavioral contrast in pigeons. The results cannot be explained by current theories, which view contrast as the product of a single general process.     

Sibling interaction: Evidence of a generational effect in maltreating infants

Theorists have long assumed that an individual's style of child-rearing was based, in large part, on his or her parents' style of parenting. The strongest evidence of such a generational effect comes from retrospective studies of disturbed adults. The present study is an attempt to provide some prospective evidence. Infants, aged 6 to 11 months, were videotaped interacting with their mother, with a sibling, and with a second adult. At each sibling age (from 2 to 10 years) one abused, one neglected, one problematic, and one normally reared infant was seen. The adult/sibling patterns of interaction were coded as abusive, neglecting, inept, or sensitive. Infant patterns were difficult, passive, and cooperative. Siblings were found to interact with the infant in a manner similar to that of their mothers suggesting that they had learned their style of interaction from their mothers. Although adequately reared siblings increased in sensitivity with age, maltreated siblings did not. The possibility that infant temperament had influenced both the mothers' and the siblings' style of interaction (and, therefore, accounted for their similarity) was tested using a second adult interactant. Adults were found to influence infants more than the reverse. These data provide evidence of a generational effect in the learning of parenting styles appearing as early as the third year of life. Moreover, they suggest that the effect is not attributable to infant temperament.     

浅谈负反馈在系统校正中的作用

本文讨论了负反馈校正的两个突出的特点与作用,在工程技术上有着广泛的应用．     

Effects of the correlation between a positive and negative US on conditioned suppression in rats

For three groups of rats, an auditory CS, presented while the animals were responding on a variable-interval schedule for food reinforcement, was terminated on half of the trials with a noncontingent footshock. For two groups, half of the trials were also followed after 5 sec by the delivery of free food. In the positively correlated condition (PC) the free food was presented on shocked trials and in the negatively correlated condition (NC) on the nonshocked trials, while the remaining group (S) never received free food. In a fourth group the shock was omitted and free food delivered on half of the trials. Although all shocked groups showed a significant suppression, the magnitude was greater for Group PC than for Groups NC and S, which did not differ. Suppression did not result from the pairing of the CS with food alone. These results do not support the counterconditioning hypothesis that the pairing of a normally noxious stimulus with food reduces its aversiveness.     

Systematic manipulation of CS-US pairings in negative CS-US correlation procedures in rats

Male albino rats were exposed to negative correlations of tone CSs and shock USs. When the number of CSs and unpaired USs was held constant, the ability of the CS to resist subsequent excitatory conditioning declined as a function of the number or proportion of CSs paired with USs; so, too, did the ability of the CS to disrupt excitation to a second CS. In one treatment, in which the rate of USs in CS presence approached that in CS absence, the CS significantly enhanced excitation to a second CS. It is concluded that the rate of USs in CS presence need not be zero for a negative correlation to produce inhibitory effects. Also discussed is the possibility that positive and negative correlation procedures may have asymmetrical effects, at least preasymptotically.     

Effects of varying sucrose reinforcers and amobarbital sodium on positive contrast in rats

The effect of quantity and quality of reinforcement on performance change following a shift to uniform high reward was studied in four groups of rats. Twenty or 200 licks of a 5% or 20% sucrose solution constituted the four incentive conditions. Two additional subject groups were run in the high (20%–200 licks) and low (5%-20 licks) reward conditions to determine how amobarbital sodium, an emotional depressant, influences incentive shift performance. All six groups received 60 preshift runway trials (6/day), followed by 30 high reward trials. Twenty-four extinction trials contrasted drugged and normal performance relating to high and low reward Postshift positive contrast appeared in all nondrugged groups. An emotional base for positive contrast is considered.     

Positive and negative successive contrast effects following multiple shifts in reward magnitude under high drive and immediate reinforcement

Multiple shifts in reward amount were given to rats in a straight runway. Both positive and negative contrast effects were observed. A positive contrast effect was observed, however, only if the shift from small to large reward occurred while the subject was evidencing a negative contrast effect. Implications for current conceptions of reinforcement contrast are discussed.