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1.
Previous experiments have shown that the negative contrast effect in consummatory behavior that occurs when rats are shifted from 32% to 4% sucrose is alleviated by the tranquilizer chlordiazepoxide (CDP). However, in these experiments, CDP was effective on the second postshift day but not on the first postshift day. The three experiments described in this paper suggest that this differential effectiveness of CDP is not due to the difference in preshift-postshift retention intervals on Day 1 (24 h) and Day 2 (48 h), but is due instead to the necessity of some degree of experience (about 5 min) with the postshift solution. These results, combined with those of an earlier study which showed elevated corticosterone in shifted animals on the second postshift day but not on the first postshift day, suggest that negative contrast may be a dynamic process, involving sequential processes of detection, evaluation, and conflict over the postshift period. It was further suggested that CDP becomes effective in moderating contrast only when the conflict stage is reached. 相似文献
2.
Rats shifted from 32% sucrose to 4% sucrose lick less than rats that experience oniy the 4% solution. Previous experiments have found this negative contrast effect to be reduced (“disinhibited”) by the addition of a novel tone in the postshift period. In Experiment 1 of this paper, the negative contrast effect was enhanced when a novel flavor was added to the sucrose solution in the postshift period. In Experiments 2–4, changes in the ambient context, even changes sufficient to produce disruptions in licking, did not alter the degree of negative contrast. Tiese results suggest that (1) rats compare rewards across substantially different contexts, (2) contrast may serve to enhance taste neophobia, and (3) a disinhibitory effect may be confined to the presentation of punctate, nontaste, novel stimuli within a familiar context. 相似文献
3.
Charles F. Flaherty Anna Greenwood Joseph Martin Mary Leszczuk 《Learning & behavior》1998,26(4):397-407
The relatedness of behavior elicited by reward reduction (successive negative contrast procedure) and behaviors produced by three animal models of anxiety (open-field emergence, elevated plus-maze, and context-shock fear conditioning) was examined by correlational and factor analytic procedures. Factor analysis (oblique rotation) indicated substantial independence among the tests: Trials 1 and 2 of the plus-maze loaded on two different factors unaccompanied by any other test; open-field emergence and context-shock fear loaded on the same factor; and negative contrast loaded on a fourth factor. However, negative contrast proved to be a dynamic process, with factor loadings changing across a 4-day postshift period—moving from an independent loading on the 1st postshift day to being clustered with context-shock fear and open-field emergence on the 2nd and 3rd postshift days to being clustered with just context-shock fear on the last postshift day. These latter data support a multistage theory of successive negative contrast. 相似文献
4.
In three experiments, we studied the consequences of ejaculation upon the frustrative or contrast response of male rats exposed
to reward downshift situations (i.e., surprising changes from 32% to 4% sucrose solutions). Similar to what has been found
after treatment with anxiolytic agents, consummatory suppression was partially reversed by previous ejaculations in a second
postshift trial (Experiments 2 and 3), such a result not having been obtained in a first postshift trial (Experiment 1). Moreover,
the effect of ejaculations upon males' behavior during a second postshift trial was transitory, disappearing when assessed
during the third and fourth postshift trials (Experiment 3). These results are in accordance with both Amsel's (1958, 1992)
frustration theory and Flaherty's (1996) multistage hypothesis of successive negative contrast; the diverse factors that are
known to modulate contrast effects are considered, including an interpretation of the present data in terms of the anxiolytic-like
effect of the ejaculation. 相似文献
5.
In a series of three experiments, rats shifted from a 32% to a 4% sucrose solution, after 10 days’ exposure to the 32% solution, exhibited a negative contrast effect in lick rate. In each experiment, shifted rats that received a novel stimulus (tone) during the postshift period exhibited a higher lick rate (smaller contrast effect) than shifted subjects not receiving the tone. This increase in lick rate resembles Pavlovian disinhibition and is interpreted as supporting an inhibitory view of successive negative contrast effects. Control conditions included in Experiments 2 and 3 favored the disinhibition interpretation of the effect of the tone, as opposed to a rate-dependency hypothesis or to the nonspecific energization of behavior. In Experiments 4–6, the tone was introduced coincident with the occurrence of a simultaneous negative contrast effect. Rather than disinhibition, a decrease in licking occurred. These results were discussed in terms of differences between successive and simultaneous contrast. 相似文献
6.
Handling of preweanlings (Days 2–15) had substantial effects on the open-field behavior of rats when tested as adults. In general, handled rats reared more, ambulated more, and defecated less than nonhandled rats. However, the handling manipulation had no effect on the degree of negative contrast that occurred when rats were shifted from 32% to 4% sucrose. Experiments 2 and 3 showed that preweaning handling did not influence sucrose neophobia in two different test situations. These data, in conjunction with those of other studies, suggest that preweaning handling may have powerful but limited effects on adult behavior, and that these effects are probably not best characterized in terms of global concepts such as emotionality. 相似文献
7.
In Experiment 1, rats received single-alternation training with 32% or 4% sucrose reward (Phase 1) followed by a shift in reward from 32% to 4%, and vice versa (Phase 2). In Phase 1, high reward facilitated alternation performance over low reward. In Phase 2, performance on rewarded trials increased as reward increased but was unchanged as reward decreased. Performance on nonrewarded trials showed negligible effects of shifts in reward. In Experiment 2, rats received goalbox placements with 32% or 4% sucrose alternated with nonreward in Phase 1; and in Phase 2, they received alternation runway training with the same or the opposite reward from that of placements. Performance on rewarded trials was faster, the higher the reward in runway training; performance on nonrewarded trials was slower, the higher the reward in placements. In Experiment 3, Phase 1 provided placements with 64%, 32%, 16%, or 4% sucrose or dry mash alternated with nonreward; Phase 2 provided alternation runway training with dry mash reward. Alternation prerformance developed more rapidly, the higher the sucrose concentration in placements. Only 64% sucrose produced performance superior to that for dry-mash placements. 相似文献
8.
拟康氏木霉胞外粗多糖经纯化得两个单一组分TPeps-1和TPeps-2．用0．25mg／mLTPeps-2处理黄瓜幼苗,处理叶在第一天就产生活性氧爆发,of含量是对照的117．5％;第二天处理中SOD活性达到峰值,为对照的135．5％;用黄瓜灰霉病菌接种黄瓜幼苗也产生了较强的诱导效应,处理叶第一天O2^-含量是对照的139．7％,第二天SOD活性为对照的141．9％;而且两组试验中未处理的系统叶中也存在较弱的诱导反应．结果说明TPeps-2能模拟病原入侵激发黄瓜叶片活性氧代谢途径． 相似文献
9.
Fred P. Valle 《Learning & behavior》1990,18(4):387-392
For 2 h prior to their daily meal of Purina Chow, rats (which were 14% below ad-lib weight levels) had access to a sucrose solution. For half (Group 16-4), the solution was alternated daily between 18% and 4%; for the other half (Group 4-4), the solution was always 4%. On 18% days, Group 16-4 consumed significantly more calories and gained significantly more weight than did Group 4-4, because of a greater consumption of sucrose calories (Purina intake was similar for the two groups). On 4% days, however, Group 16-4 consumed both significantly fewer sucrose calories and significantly fewer Purina calories than did Group 4-4. These two contrast effects resulted in a 17% shortfall in total caloric intake for Group 16-4 on 4% days. As a consequence, Group 16-4 showed a significant drop in body weight, compared to Group 4-4, on 4% days. A second experiment was carried out to investigate whether the contrast-induced reduction in Purina intake shown by Group 16-4 on 4% days would be eliminated if (1) a 30-min interval separated sucrose ingestion from Purina ingestion, or (2) a 25-min interval plus 5-mmn exposure to 16% sucrose separated ingestion of 4% sucrose from Purina ingestion. Purina intake was still suppressed in Group 16-4 under both conditions. 相似文献
10.
Charles F. Flaherty Patricia S. Grigson Cynthia Coppotelli Colin Mitchell 《Learning & behavior》1996,24(1):68-81
Intake of a 0.15% saccharin solution was suppressed when it was followed by a 32% sucrose solution in brief daily pairings. With equal access durations to the two solutions, intervals of intermediate duration (2 or 3 min) produced a larger contrast than more extreme intervals (1 or 10 min). There was no evidence of inhibition of delay with the 10-min interval (Experiments 1A and 1B). When access times were asymmetrical, longer access time to the first solution reduced contrast, whereas longer access time to the second solution enhanced contrast (Experiment 2). Contrast was greater when the two solutions were presented at consistent and separate spatial locations than when location was changed randomly or when both solutions were presented in sequence at the same location. However, a degree of contrast occurred in all conditions (Experiment 3). Experiment 4, conducted with the solutions in opposite arms of a T-maze, showed that anticipatory approach to the location correlated with the 32% sucrose solution developed prior to lick suppression on the saccharin solution. However, within daily sessions, there was a reliable increase in contrast without correlated changes in anticipatory-approach behavior. Access-time effects were attributed to altered reward values, whereas spatial-separation effects suggest that goal-directed responses contribute to, but do not cause, anticipatory contrast. 相似文献
11.
Previous experiments have shown that the intake of a 0.15% saccharin solution is suppressed if saccharin access is followed by access to 32 % sucrose in brief daily pairings. The present experiments found that: (1) the degree of suppression was not altered when no time elapsed between presentation of the two solutions each day (15 sec had been the minimum in previous experiments and was used as the control in this experiment); (2) the degree of suppression was not altered by chlordiazepoxide (6, 12, or 20 mg/kg), although the drug had large appetite-stimulating effects; (3) suppression was not influenced by amphetamine (0.25 or 0.50 mg/kg); and (4) contrast could be established or eliminated, even after extended training, by manipulating the sequences of solutions presented (saccharin-saccharin or saccharin-sucrose). The results were interpreted in terms of a contrast effect based on the learned anticipation of a preferred substance. The chlordiazepoxide data suggest that this contrast is different from successive negative contrast, and the intersolution interval data suggest that the occurrence of contrast rather than a reinforcement effect is not due to a time gap between presentations of the two solutions. 相似文献
12.
An animal’s appetitive behavior is not a fixed response to current stimulation but can be affected by the anticipation of future events. For example, rats regularly given access to a moderately valued solution followed by a higher value solution (e.g., 4 % sucrose → 32 % sucrose) consume less of the initial solution than in control conditions where the initial solution is not followed by a higher value solution (e.g., 4 % sucrose → 4 % sucrose). Previous analyses have suggested that this negative anticipatory contrast effect does not depend on the “expectation” of a valuable stimulus producing a functional devaluation of a currently available stimulus of lesser value. In a within-subjects anticipatory contrast procedure, this study revealed that both consumption and the mean size of licking clusters were smaller for a 4 % sucrose solution on days when it preceded 32 % sucrose than on days when 4 % preceded 4 %. Since lick cluster size typically bears a positive monotonic relationship with the concentration of palatable solutions, this reduction is indicative of a decrease in the palatability/hedonic value of the solution subject to contrast. As such, we provide direct evidence that negative anticipatory contrast does produce a functional devaluation of the solution, thus challenging prevailing theoretical assumptions. 相似文献
13.
In four experiments, the once daily availability of saccharin (.15%) preceded the availability of sucrose (32% or 2%). Experiment 1 showed that the intake of saccharin was reduced when it preceded 32% sucrose but not when it preceded 2% sucrose, as compared with saccharin-alone conditions. Experiment 2 showed that less saccharin was consumed when the saccharin preceded sucrose by 5 min than when there was a 30-min intersolution interval. Experiment 3 replicated this finding and showed that the presentation of the two solutions through the same or different access holes in the apparatus was not relevant to the result. Experiment 4 showed that there was an inverse relationship between saccharin intake and the length of the intersolution interval in the range of 1 to 30 min. These data were interpreted to indicate that the animals learn the predictive relationship between the saccharin and sucrose solutions and that the intake of the saccharin is reduced by an anticipatory contrast mechanism—a mechanism that may have restricted temporal parameters. 相似文献
14.
目的：观察开心散含药血清对皮质酮（corticosterone）损伤大鼠大脑皮质星形胶质细胞CTXTNA2的影响。方法：制备开心散含药血清（500mg·kg-1）、阳性药氟西汀含药血清（10mg·kg-1）、普通大鼠血清。细胞实验中采用皮质酮损伤CTXTNA2细胞建立体外抑郁模型,MTT法检测开心散对皮质酮所致细胞损伤的影响以及磷脂酰肌醇3-激酶（phosphatidylinositol 3-kinase,P13K）信号通路抑制剂的干预作用;采用Western Blotting法检验相关信号通路蛋白表达变化情况。结果：皮质酮浓度为200μm01·L-1时,细胞活力抑制率可稳定在60％,浓度依赖性较好;开心散含药血清均能够显著提高皮质酮损伤细胞的存活率,而给予P13K相关通路的抑制剂后,开心散保护作用被逆转,Western Blotting结果显示给予开心散含药血清能够逆转皮质酮损伤后P13K及蛋白激酶B（protein kinase B,AKT）1／2蛋白表达下降的趋势。结论：开心散含药血清对皮质酮所致的CTXTNA2细胞损伤具有明显保护作用,其保护机制可能与P13K信号通路有关。 相似文献
15.
Rats were shifted from 32% sucrose solution in one apparatus to a 4% sucrose solution in a different apparatus, and the performance of these animals was compared to rats that received the 4% solution in both situations. Transsituational negative contrast effects were found in both consummatory and instrumental measures of behavior and, in addition, these contrast effects were found to have some elements in common with both successive and simultaneous contrast effects, but were identical to neither. 相似文献
16.
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. 相似文献
17.
18.
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. 相似文献
19.
Bruce R. Lombardi 《Learning & behavior》1980,8(4):617-620
In two experiments, a successive negative contrast effect in licking was produced by shifting rats from 32% to 4% sucrose solution. Subsequent to the downshift in reward, the rats were tested for licking either a plain 12% sucrose solution or 12% plus a neutral flavor. Licking for the 12% solution was depressed in downshifted rats when a flavor was present, regardless of whether this flavor was novel or had been present in the shift solution. The results were interpreted in terms of an enhancement of neophobia by reward reduction. 相似文献
20.
R. A. Burns 《Learning & behavior》1976,4(4):473-479
Two experiments assessed the role of aftereffect learning in rats rewarded with sucrose solutions. In Experiment 1, rats were trained in a single straight runway for two trials on each of 18 days, each trial terminating with either large (20% scurose) or small (3% sucrose) reward. The ITI was 3–5 min. The sequence of daily rewards for each of four groups was small-small (SS), small-large, (SL), large-small (LS), or large-large (LL). Response patterning and a simultaneous negative contrast effect were observed in LS and SL relative to the consistently rewarded controls. During 10 massed extinction trials, resistance to extinction was greatest for Group SL, followed in order by Groups SS, LL, and LS. Experiment 2 examined single alternation of large and small rewards administered for 10 trials on each of 31 days with an ITI of 60 sec. Reward for one group was 20% or 3% sucrose while another received 1 or 10 45-mg Noyes pellets. Appropriate patterning developed only in the food-pellet rewarded animals. The overall results suggest that sucrose rewards may produce high-amplitude and long-duration aftereffects which interfere with learning in designs employing several massed daily trials, but which may facilitate learning—relative to food-pellet rewards—with longer intertrial intervals and fewer daily trials. 相似文献