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1.
Gavan P. McNally Marika C. Gorrisen Lee-fay Low R. Frederick Westbrook 《Learning & behavior》1999,27(4):416-425
Rats were used in four experiments to study the effects on behavior and pain sensitivity of exposure to a context previously
paired with footshock or injection of the emetic drug lithium chloride (LiCl). Exposure to a context previously paired with
footshock or injection of LiCl provoked the species-typical defense response of freezing (Experiments 1A and 1B). Exposure
to a context previously paired with footshock additionally produced hypoalgesia when rats were tested using the tailflick
test (Experiment 1A). By contrast, exposure to a context previously paired with injection of LiCl produced hyperalgesia when
rats were tested using the tailflick test (Experiment 1B). However, exposure to a context previously paired with injection
of LiCl did provoke hypoalgesia when rats were tested for pain sensitivity using either the hotplate or formalin tests (Experiment
2), which was mediated by the release of endogenous opioid peptides (Experiment 3). These results are discussed with reference
to the processes governing associative regulation of defensive behavior and pain control. 相似文献
2.
Contribution of conditioned opioid analgesia to the shock-induced associative US-preexposure deficit
The modulatory effect of conditioned opioid analgesia on learning in the US-preexposure paradigm was examined in three experiments using water-deprived rats. In Experiment 1, it was found that tailflick latencies increased immediately after the rats were exposed to a context in which footshock had previously been administered. Prolonged nonreinforced exposure to the context attenuated this analgesia. Experiment 2 tested the possibility that the effectiveness of CS-US pairings in an excitatory context might be reduced by a conditioned analgesic response that lessens the perceived intensity of the US. Administration of the opiate antagonist naloxone prior to CS-US pairings in the excitatory context reduced the US-preexposure deficit—that is, the retarded response to the CS—but did not eliminate it, suggesting that part of the observed deficit resulted from conditioned activation of the endogenous opioid system. In Experiment 3, it was found that exposure to the excitatory context immediately prior to a CS-US pairing in an associatively neutral context resulted in a conditioned response deficit, indicating that the analgesia elicited by the excitatory context was sufficient to reduce US effectiveness. In combination with other recent reports, these results suggest that the associative deficit resulting from preexposure to a shock US may, in certain instances, represent the sum of several different associative processes. 相似文献
3.
In four conditioned suppression experiments with rats (Rattus norvegicus), backward pairings of a shock unconditioned stimulus (US) and a tone conditioned stimulus (CS) eliminated an already established conditioned response (CR), but there was recovery of the CR if the shock was later withheld. In Experiment 1, there was recovery after backward pairings, regardless of whether the period after the US was normally shock free or not. In Experiment 2, the occurrence of recovery depended on the CS’s being presented closely after the US in response elimination. Levels of recovery were positively correlated with the resistance of the response to elimination during backward pairings (Experiments 3 and 4). Taken together, these data support the notion that recovery after backward pairings is a form of renewal (see, e.g., Bouton, 1991) and is not due toprotection from extinction. 相似文献
4.
David S. Tuber 《Learning & behavior》1986,14(4):421-426
Based upon considerations raised by Soviet research, the role of relative stimulus intensity, or dominance, in the unconditioned stimulus-unconditioned stimulus (US-US) paradigm was investigated under circumstances presumed favorable to the backward conditioned response (CR). Using the classically conditioned forelimb response of the cat, a brief shock (USD delivered to one forepaw preceded a shock (US2) to the opposite forepaw in paired conditioning fashion; subjects in the control group received explicitly unpaired presentations of the stimuli. Conditioning in both the forward and backward directions was evaluated by the appearance of contralateral CRs on test trials to each of the USs. In Experiment 1, a ratio of the intensities between US1 and US2 of 100:80 was used to create a relative dominance in favor of the backward CR. In addition, to evaluate the suggestion that the appearance of the backward CR is retarded in the Pavlovian paradigm, overtraining was provided to a forward conditioning criterion of 200%. In Experiment 2, the cats were exposed to successive reductions in the intensity of US2 to verify manipulations of dominance reportedly involved in the reactivation of a latent backward CR. Although forward conditioning was readily established to USl, there was no evidence of back-ward conditioning to US2 under any of the conditions. 相似文献
5.
Three conditioned lick suppression experiments with rats were performed to assess the influence, following compound training
of two stimuli (A and X) with the same outcome (AX-O trials), of extending training of the blocking association (i.e., A-O)
on responding to the target stimulus (X) at test. In Experiment 1, backward blocking was attenuated when the blocking association
was extensively trained. Experiment 2 showed that forward blocking was also attenuated by extensive further training of the
blocking association following the AX-O trials. Experiment 3 contrasted candidate explanations of the results of Experiments
1 and 2 and demonstrated that these results are consistent with the framework of the extended comparator hypothesis (Denniston,
Savastano, & Miller, 2001). 相似文献
6.
Conditioned lick suppression in rats was used to explore the role of timing in trace conditioning. In Experiment 1, two groups of rats were exposed to pairings of a CS (CS1) with a US, under conditions in which the interstimulus interval (ISI) that separated CS1 offset and US onset was either 0 or 5 sec. Two additional groups were also exposed to the same CS1→US pairings with either a 0 or a 5-sec ISI, and then received “backward” second-order conditioning in which CS1 was immediately followed by a novel CS2 (i.e., CS1→CS2). A trace conditioning deficit was observed in that the CS1 conditioned with the 5-sec gap supported less excitatory responding than the CS1 conditioned with the 0-sec gap. However, CS2 elicited more conditioned responding in the group trained with the 5-sec CS1-US gap than in the group trained with the 0-sec CS1-US gap. Thus, the CS1-US interval had inverse effects on first- and second-order conditioned responding. Experiment 2 was conducted as a sensory preconditioning analogue to Experiment 1. In Experiment 2, rats received the CS1?CS2 pairings prior to the CS1→US pairings (in which CS1 was again conditioned with either a 0 or a 5-sec ISI). Experiment 2 showed a dissociation between first- and second-order conditioned responding similar to that observed in Experiment 1. These outcomes are not compatible with the view that differences in responding to CSs conditioned with different ISIs are mediated exclusively by differences in associative value. The results are discussed in the framework of the temporal coding hypothesis, according to which temporal relationships between events are encoded in elementary associations. 相似文献
7.
Robert A. Rescorla 《Learning & behavior》1997,25(2):200-209
In five experiments, rats were given Pavlovian pairings of auditory and visual stimuli with delivery of food pellets. Experiment 1 found greater responding to an AB compound after training with the individual A and B stimuli, compared with responding both to the A and B elements and to a separately trained CD compound. Experiment 2 found this enhanced responding to depend on the associative strengths of A and B. In Experiment 3, responding was greater to a CD compound than to the other compounds after an AB-, AD+, BC+ training procedure. In Experiment 4, responding to an AB compound was greater than that to the elements after A was reinforced on a 100% schedule and B on a 50% schedule. In Experiment 5, responding to an AC compound was greater than that to either A or C after an AB+, CD+, A-training procedure. A configural theory, such as that proposed by Pearce (1987), anticipates summation in none of these procedures, unless the conditioned context is assumed to have a salience greater than zero. In order to predict summation in Experiments 3, 4, and 5, a context salience greater than that of the elements must be assumed. However, such an assumption also anticipates that extinction of a 100% stimulus should eliminate responding to a 50% stimulus. The results of Experiment 3 contradicted that prediction. These results conform better to the expectations of elemental models of conditioning. 相似文献
8.
Four experiments examined the effects of separate presentations of shock on conditioned suppression of instrumental responding evoked by a CS previously paired with shock. Experiment 1 showed that conditioned suppression of responding resulting from noise-shock pairings increased as a function of time after the initial noise-shock pairings. However, it also showed that this time-dependent increase in conditioned suppression of responding could be attenuated by presentations of light-shock pairings immediately prior to the test of the noise CS. Experiment 2 showed that this attenuation effect can be produced by presentations of either light-shock pairings or shock alone. Experiment 3 showed that the magnitude of this attenuation effect was directly related to the temporal proximity of the light-shock pairings to the test of the noise CS. Experiment 4 showed that the magnitude of this attenuation effect was inversely related to the intensity of separate shock presentations. 相似文献
9.
Acquisition, extinction, and transfer of facilitation were explored in a series of experiments with C57BL/6J mice. With a
procedure in which an auditory target was followed by food only in the presence of a visual facilitator, Experiments 1—4 showed
that the facilitator promoted magazine entries to the auditory target. This enhancement effect was eliminated by training
the facilitator as a conditioned inhibitor (Experiments 1 and 3B). Enhancement was also reduced by nonreinforced presentations
of the facilitator in a discrimination procedure (Experiment 1) and by simple nonreinforcement of the facilitator (Experiments
2, 3A, and 4). In contrast to the results obtained with a facilitator, simple nonreinforcement of an inhibitor, a visual cue
that had signaled when an auditory target would not be reinforced, did not reduce its ability to modulate responding to that
target (Experiment 4). However, both the facilitator and the inhibitor were found to transfer their modulatory effects to
other targets (Experiment 4). Finally, mice demonstrated no evidence of differential responding on a biconditional discrimination
procedure in which one auditory target (A1) was reinforced in the presence of one visual stimulus (L1) but not in the presence
of another (L2), and a different auditory target (A2) was reinforced in L2 but not in L1 (Experiment 5). The implications
of these results for analysis of the function of a facilitator are discussed. 相似文献
10.
Three experiments with rat subjects examined the effects of contextual stimuli on performance in appetitive conditioning. A 10-sec tone conditioned stimulus (CS) was paired with a food-pellet unconditioned stimulus (US); conditioning was indexed by the observation of headjerking, a response of the rat to auditory stimuli associated with food. In Experiment 1, a context switch following initial conditioning did not affect conditioned responding to the tone; however, when the response was extinguished in the different context, a return to the original conditioning context “renewed” extinguished responding. These results were replicated in Experiments 2 and 3 after equating exposure to the two contexts (Experiment 2) and massing the conditioning and extinction trials (Experiment 3). The results of Experiment 1 also demonstrated that separate exposure to the US following extinction reinstates extinguished responding to the tone; this effect was further shown to depend at least partly on presenting the US in the context in which testing is to occur (Experiments 2 and 3). Overall, the results are consistent with previous data from aversive conditioning procedures. In either appetitive or aversive conditioning, the context may be especially important in affecting performance after extinction. 相似文献
11.
In Experiments 1 and 2, rats were exposed to two compound flavors, AX and BX, containing one flavor in common (X). Following this exposure phase, an aversion was conditioned to A in the experimental group by pairing its consumption with an injection of lithium, while a control group drank A without being poisoned. The effect of this treatment was to establish B as a conditioned inhibitor. In Experiment 1, experimental animals were slower than controls to condition an aversion to B when its consumption was paired with lithium (a retardation test of conditioned inhibition). In Experiment 2, B alleviated the suppression of intake of another flavor previously paired with lithium (a summation test). Experiments 3 and 4 established that these effects depended upon prolonged prior exposure to AX and BX. 相似文献
12.
Michael Domjan 《Learning & behavior》1978,6(2):133-142
Taste aversions were conditioned by exposing subjects to a 1.0% saccharin solution 30 min after an injection of lithium chloride. The aversion learning was disrupted if subjects had also received an additional lithium injection some time earlier (Experiments 1–3). This interference effect of US preexposure was a decreasing function of the preexposure interval, beyond the optimal interval (105 min) for observing the phenomenon (Experiment 1), and was directly related to the dose of the preexposure injection (Experiment 2). No interference with conditioning occurred at short (e.g., 30-min) preexposure intervals (Experiment 1), probably because under these circumstances the preexposure injection itself conditioned a strong aversion (Experiment 4). At moderate (105-min) but not at short (30-min) preexposure intervals, the interference with aversions learned as a result of taste exposure following drug injection was comparable to the interference with learning in a more conventional forward conditioning procedure (Experiments 3 and 4). These findings are similar to previously documented effects of proximal CS- and US-preexposure and are consistent with recent stimulus rehearsal and opponent-process theories. 相似文献
13.
Todd R. Schachtman Wesley J. Kasprow Robert C. Meyer Mark J. Bourne Julie A. Hart 《Learning & behavior》1992,20(3):207-218
Using a conditioned taste aversion preparation overshadowing of flavor-illness association was produced through the presentation of a second flavor during the interval between the first flavor and illness. The modulatory effects of extinguishing the association between the second (over-shadowing) flavor and illness on conditioned responding to the target flavor was investigated. In Experiment 1, we found that, following one-trial overshadowing, extinction of the overshadowing flavor had no effect on conditioned responding to the target flavor. In Experiment 2, we found a similar absence of an effect of extinction of the overshadowing stimulus in a multitrial over-shadowing paradigm. Experiment 3 confirmed the results of Experiments 1 and 2 using conditioning parameters that were designed to weaken the association between the overshadowed flavor and illness. In Experiments 4 and 5, we used simultaneous presentation of the flavors during conditioning and obtained a weakened aversion to the overshadowed flavor when the overshadowing CS was extinguished. These findings are inconsistent with previous observations in conditioned fear preparations that suggest that extinction of the association between the overshadowing stimulus and the unconditioned stimulus attenuates overshadowing. Possible reasons for the discrepant results are discussed. 相似文献
14.
Rats trained in one context to use stimuli arising from food deprivation as discriminative signals for shock were tested in other contexts to assess the basis of conditioned responding (i.e., freezing or behavioral immobility). In Experiment 1, discriminative control by 24-h food-deprivation cues failed to promote transfer responding in a test context that had no association with shock. This indicated that food deprivation cues had little direct excitatory power. However, transfer of behavioral control by 24-h food-deprivation cues was obtained in a context paired with shock only when the rats were 19 h water deprived. This finding agrees with the idea that food-deprivation cues become conditioned modulators of the capacity of external stimuli to activate their association with an unconditioned stimulus. In Experiment 2, rats trained to use 24-h food-deprivation cues as signals for shock exhibited significantly greater transfer performance when the transfer context had undergone partial extinction relative to when the transfer context had undergone only simple excitatory training. This finding with deprivation cues and transfer contexts (1) paralleled earlier results obtained with discrete (auditory and visual) conditioned modulators and transfer targets, and (2) posed difficulties for associative summation and generalization interpretations of transfer performance. 相似文献
15.
Dale Swartzentruber 《Learning & behavior》1993,21(1):14-22
Two autoshaping experiments with pigeons examined contextual control of responding to conditioned stimuli (CSs) when separate phases of reinforcement and nonreinforcement occurred in different contexts. In Experiment 1, a CS was first conditioned in Context A prior to nonreinforcement in Context B. In Experiment 2, a conditional discrimination reversal procedure was employed in which one CS was first reinforced in A prior to nonreinforcement in B, and another CS was first nonreinforced in A and then reinforced in B. In both experiments, the extent of contextual control was assessed by testing the CSs in A and B. The CS specificity of control was assessed by examining control of CSs that had been treated like the original CSs, but in a different pair of contexts. The results show that contexts control responding to CSs through a CS-specific mechanism, as well as through a mechanism that is independent of the identity of the CS. However, the extent to which control is mediated by a CS-independent mechanism depends on the training history of the CS. 相似文献
16.
The present research examined the temporal distribution of responding in a lick suppression paradigm. In Experiment 1, rats were trained with either a 30- or a 120-s conditioned stimulus (CS), which was followed either by a footshock (unconditioned
stimulus [US]) or nothing. Licking during the CS was suppressed only in the former condition. Suppression was more pronounced
early in the CS. In Experiment 2, rats were exposed to two 30-s or two 120-s CSs, with delivery of the shock being contingent on CS1 for half of the animals
and on CS2 for the other half. For both the paired and the unpaired conditions, suppression at the beginning of CS1 was observed
for all the groups. By discounting the possibility of generalization between CS1 and CS2, it appears that this initial suppression
was not a conditioned response to the CS, but an unconditioned one due to mere exposure to the shock US. 相似文献
17.
Learning & Behavior - Four experiments with rat subjects assessed conditioned analgesia evoked by a discrete visual CS repeatedly paired with a shock US. In Experiment 1, rats that received... 相似文献
18.
In two pairs of three-stage conditioned taste aversion experiments, we examined the effects of delay interval (1 or 21 days)
between the second and third stages, and of context in which the animals spent the delay (same as or different from the context
of the other stages) on latent inhibition (LI) and spontaneous recovery following extinction. In the LI experiments (Experiments
1A and 1B), the first stage comprised nonreinforced presentations to saccharin or to water. In the second stage, rats were
conditioned by saccharin paired with LiCl. In the extinction experiments (Experiments 2A and 2B), the order of the stages
was reversed. For all experiments, Stage 3, the test stage, consisted of three presentations of saccharin alone. There was
a super-LI effect in the saccharin-preexposed group that spent the 21- day delay in the different context (Experiment 1A).
When the delay was spent in the same context, there was no difference in the amount of LI between the short- and long-delay
groups (Experiment 1B). Conversely, there was a spontaneous recovery effect in the long-delay/same-context group (Experiment
2B), but not in the long-delay/different-context group (Experiment 2A). The pattern of results, incompatible with current
explanations of delay-induced changes in memory performance, was interpreted in terms of an interaction between the delay
conditions (same or different delay context), which modulate the extinction of previously acquired context-CS-nothing associations
(during CS-alone presentations), and primacy effects. 相似文献
19.
In a conditioned suppression experiment, rats received a single, massed session of conditioning in which one backward conditioned inhibitory stimulus (CS-) followed shocks that were signaled by a visual cue, and a second backward CS-followed shocks that were unsignaled. Conditioning was preceded by a preexposure phase in which some groups of rats were preexposed to unsignaled shock, while others were not preexposed and remained in the experimental apparatus in the absence of shock. The groups were further distinguished by whether US preexposure and conditioning occurred in the same or different contexts, and by whether conditioning began immediately or after a 24-h rest period in the home cage. Although the conditioning itself was effective in establishing the visual cue as a conditioned excitor in the nonpreexposed groups, it was not effective in establishing the two backward cues as reliable inhibitors with either signaled or unsignaled USs. After 210 US preexposures, however, the same conditioning sessions did yield conditioned inhibition to both CS-s. A 24-h rest period in the home cage reduced the magnitude of, but did not completely abolish, the facilitative effect of US preexposure on inhibitory conditioning. Other tests demonstrated that US preexposure had retarded excitatory conditioning to the visual cue. This interference with excitatory conditioning was unchanged in magnitude after the 24-h rest period. The facilitative effect of US preexposure on backward inhibitory conditioning, and the interference effect on excitatory conditioning, were both eliminated by a change in context between US preexposure and conditioning. These observations encourage predominantly associative accounts of the effects, but allow for a small nonassociative habituation component. 相似文献
20.
In two experiments with rat subjects, we examined the effects of a retention interval on performance in two conditioning paradigms in which a conditioned stimulus (CS) was associated with different unconditioned stimuli (USs) in successive phases of the experiment- Experiment 1 was designed to examine aversive-appetitive transfer, in which the CS is associated with shock and then food; Experiment 2 was designed to examine appetitive-aversive transfer, in which the CS is associated with food and then shock. Aversive and appetitive conditioned responses (freezing and head-jerk responding, respectively) were scored from videotape. In both experiments, a 28-day retention interval following the end of Phase 2 caused a recovery of the Phase 1 response and a resuppression of the Phase 2 response. The results suggest that the original association is not destroyed when the CS is associated with a new US in Phase 2. They also suggest that both retroactive and proactive interference effects may result-from interference with performance output rather than a disruption or loss of what is learned during or stored from the target phase. 相似文献