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1.
Classical eyeblink conditioning (EBC) has been widely used to probe cerebellar function in humans and nonhuman mammals. Although the neural pathways governing behavior in this task are well understood and fairly discrete, it remains unclear in the human literature how conditioned stimuli (CSs) of different modalities (e.g., visual and auditory) influence the exhibition of conditioned responses (CRs). In the present study, therefore, CRs to a visual CS and an auditory CS were examined with the single-cue delay EBC procedure. An initial experiment (N=61) was conducted to identify visual and auditory stimuli that had equal perceived intensities. Using these perceptually equivalent stimuli, a second group of 25 subjects completed auditory and visual EBC procedures in two testing sessions 5–8 days apart. Whereas the acquisition of CRs was similar between the CS modality conditions, the timing of the CRs differed such that earlier CR onset and peak latencies were associated with the visual CS. In addition, CR timing improved across testing sessions, as indicated by the later CR peak latencies exhibited during the second testing session, as compared with the first.  相似文献   

2.
A comparison was made of heart-rate (HR) responses of restrained rats to CSs that were part of an explicitly unpaired or a truly random control procedure. Subsequent to these procedures, an assessment was made of the relative capacities of these CSs to affect an established HR CR in a combined-cue paradigm and to impede the development of a HR CR in a reversal-conditioning situation. The principal findings were (1) that the explicitly unpaired and truly random CSs generated HR responses of opposite direction, i.e., HR acceleration vs. HR deceleration, respectively, and (2) that conditioning of a decelerative HR CR to the CS that had earlier been employed in the explicitly unpaired procedure was retarded compared to what was obtained to the truly random CS. The two CSs did not have reliably different effects in the combined-cue test. It was suggested that the truly random CS may have produced both associative and nonassociative influences on HR. It was hypothesized further than the explicitly unpaired CS may have acquired the capacity to function as a conditioned inhibiting stimulus.  相似文献   

3.
Male and female rabbits received Pavlovian conditioning in which a 1, 216-Hz tone served as the CS and a 3-mA paraorbital electric shock train served as the US. Eyeblink (EB) and heart rate (HR) CRs were assessed. Half of the animals received prior exposure to the CS, while half were restrained in the chamber for a similar length of time but did not receive prior CS exposure. Different groups of each sex received three different CS intensities including 60, 75, and 90 dB (SPL) during both preexposure and conditioning. The results revealed that latent inhibition of the EB CR occurred only at the intermediate CS intensity, as indicated by a significant impairment of EB conditioning in this group. However, the magnitude of the decelerative HR CR was attenuated by prior CS exposure at all three CS intensities. Females showed faster EB conditioning than males, but latent inhibition occurred in both sexes. These results suggest that somatomotor and autonomic systems are affected differently by prior CS exposure.  相似文献   

4.
Following classical conditioning to a shock-reinforced tone CS (T1+), heart rate (HR) of three groups of rats was examined in response to a new reinforced tone (T2+) and a nonreinforced light (L?) CS given during conditioned inhibition (T2+ vs. T1L?), discrimination conditioning (T2+ vs. L?), or explicitly unpaired (T2/L? vs. US alone) procedures. Decelerative HR reactions occurred to the reinforced T2+ and T2+ CSs. To the respective nonreinforced CSs, the conditioned inhibition group displayed diminished but sizable HR deceleration, the discrimination group showed near-zero responding, and the explicitly upaired group showed HR acceleration. Subsequent reversal conditioning to L was retarded in the conditioned inhibition and explicitly unpaired groups relative to the discrimination group. Group differences on combined-cue [T2/L?) trials were not found. Both the HR responses during inhibitory training and the reversal-conditioning impairments suggest that inhibition may have been established to L? in the conditioned inhibition and explicitly unpaired groups.  相似文献   

5.
To determine whether the magnitude of heart rate (HR) slowing induced by classical conditioning contingencies is comparable under a broad range of stimulus conditions, experiments were conducted in which rabbits were exposed to tones, increases in illumination, or vibratory stimuli as conditioned stimuli (CSs) and in which paraorbital electric shocks, corneal airpuffs, or intraoral pulses of water served as unconditioned stimuli (USs). The results indicated that conditioned bradycardia was elicited by all three CSs. Moreover, when a corneal airpuff served as the US, small but reliable CS-evoked HR decelerations also occurred. Finally, CS-evoked HR slowing also occurred in response to a tone CS employed in an appetitive task, in which water was the US. These findings suggest that HR slowing is a general phenomenon that occurs when rabbits are exposed to signals that systematically predict aversive or appetitive consequences according to a Pavlovian conditioning paradigm.  相似文献   

6.
This article is a review of the results of a series of experiments designed to identify brain systems involved in appetitive conditioning of rats. It discusses some of their implications for behavioral theories of learning, especially those that concern changes in processing of conditioned stimuli (CSs). Evidence is presented which suggests that separable brain circuits are involved in (1) the production of CS-dependent conditioned orienting responses, (2) the enhancement of CS associability produced when expectancies about upcoming events are violated, (3) the reduction of CS associability produced when stimuli are consistent predictors of other events or are presented without consequence, and (4) the abilities of CSs to serve as reinforcers for second-order conditioning and to be sensitive to postconditioning changes in the value of the unconditioned stimulus (US). Finally, none of these circuits seems critical for normal acquisition of the most common indicator of Pavlovian conditioning, US-dependent conditioned responses (CRs). Although the independence of brain pathways does not demand independence of behavioral function, clustering of behavioral phenomena on anatomical grounds may provide useful guides for constructing behavior theories.  相似文献   

7.
Rabbits under high or moderate water deprivation received in Stage 1 either paired (CS+), unpaired (CS?), or no-tone/shock presentations, with the pairings being appropriate for nictitating membrane conditioning. In Stage 2, all groups were given paired tone and water deliveries for jaw-movement conditioning, while, in Stage 3, all group received the tone and shock paired together for membrane conditioning. In Stage 2, the previously established aversive CS+ suppressed jaw-movement conditioning under high deprivation, and membrane CR decrements were directly related to deprivation. Also in Stage 2, the aversive CS? raised jaw-movement conditioning under moderate deprivation. In Stage 3, membrane CR performance immediately returned in the aversive CS+ group. For the other groups, conditioning was faster under high, relative to moderate, deprivation; however, the initial membrane CR occurrence required more trials if unpaired presentations were used in Stage 1. These results suggest that CSs can acquire both opponent-process and associative effects expressed according to the prevailing training conditions.  相似文献   

8.
The behavioral CRs elicited by a drug-paired contextual cue in rats were measured in a series of experiments. The first three experiments measured the pattern of CRs elicited by a lithiumand an amphetamine-paired CS chamber. The final experiment measured the pattern of URs elicited by lithium or amphetamine when administered in the same chamber. The suppression of grooming-related activities (body washing, face washing, and/or scratching) appeared as a nonspecific effect of both drug USs that was capable of becoming conditioned to the contextual chamber cue. A number of other behaviors differed among conditions, which provides evidence that contextual cue-drug associations are drug-specific. Of the behaviors that differed between the two US drug conditions, lithium CRs showed evidence of behavioral activation (enhanced rearing and limb flicking), but amphetamine CRs showed evidence of behavioral suppression (line crossing, rearing, and shaking). The UR patterns shared some similar and some dissimilar elements of the CR patterns elicited by the CS chamber for both lithium and amphetamine; in fact, by the activity and rearing measures, the URs and CRs were opposite in direction. The results exclusively supported neither stimulus substitution nor conditioned compensatory response accounts of Pavlovian conditioning; instead, each process appears to have accounted for different components of the overall CR pattern.  相似文献   

9.
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   

10.
Preweanling rats, 16 days of age, responded to an olfactory conditioned stimulus (CS) paired with a shock unconditioned stimulus (US) with increases in heart rate and behavioral activation. In two experiments this finding was replicated and, in addition, it was found that the form of these conditioned responses (CRs) changed after a retention interval. When tested 24 h after CS-US pairings, the subjects displayed a decrease in heart rate accompanied by CS-elicited freezing. Giving two unsignaled shocks prior to the delayed test effectively reinstated the tachycardia and behavioral arousal CRs. The results are discussed in terms of contextual influences on the form of the CR and how changes in the magnitude of context fear may alter responding to an olfactory CS.  相似文献   

11.
Three experiments with rat subjects sought to enhance one-trial excitatory simultaneous and backward fear conditioning by using a two-element compound conditioned stimulus (CS) instead of only a single element. During conditioning, experimental groups received a 4-sec CS either coextensively with a 1-mA grid-shock unconditioned stimulus (US) or immediately after US termination. In subsequent tests, CSs evoked more lick suppression and freezing in these groups than in various controls. Compound CSs evoked more lick suppression and freezing than did CS elements, but did so equally for experimental and control groups. Therefore, the use of compounds did not enhance conditioning. Unexpectedly, an explicitly unpaired control in which CS followed US termination by 3 min tended to show more CS-evoked suppression and freezing than did a control in which CS preceded US onset by 3 min. This result raises the possibility that associations between the CS and the training context might engender responding to backward-paired CSs.  相似文献   

12.
Twenty-eight male albino rats were given a single 4-sec 1-mA electric-grid-shock unconditioned stimulus (US). In the same session they received two 12-sec conditioned stimuli (CSs). One CS (explicitly unpaired) terminated 180 sec before the US began; the other (backward paired) began immediately after the US terminated. The CSs used were a 1000-Hz 85-dB tone and an 84-dB click; their roles were counterbalanced. Over the next 2 days, each CS was presented for 2 min while the rats drank from a water bottle. The backward-paired CS was found to suppress licking more than the explicitly unpaired CS. This suppression was accompanied by an increase in defensive behavior (freezing and freeze/nod) and by a decrease in other activity. The suppression did not seem to be due to a maintained or enhanced CS-orienting response reflex, nor could it be attributed to an adventitiously reinforced interfering operant. The results support the presumption made in previous reports that the lick suppression evoked by a backward CS reflected one-trial backward excitatory fear conditioning.  相似文献   

13.
Current research on adult-child interaction has stressed the importance of some conversational tactics for the development of communicative competence in children. The conversational device used in the presence of ambiguity and incomprehension is the clarification request (CR), an interrogative utterance by which the speaker asks for explanation, confirmation or repetition of an utterance previously produced by the listener, but which has not been perfectly understood. In this research we analyzed several aspects of nursery school teachers use of the clarification request with children of three different age groups (10–17 months; 21–26 months and 28–37 months). Using audio-recordings of naturally occurring teacher-child interactions, the following features were analyzed: 1) the quantitative distribution of CRs in teacher’s language according to the children’s age; 2) the form of the CRs; 3) their function; 4) the conversational sequences containing CRs. The results suggest that the teacher’s use of CRs is guided by their knowledge and evaluation of the children’s developing communicative competence. The distribution of CRs in the various forms and function that we indentified seem to follow the same general path isolated in the previous studies, collected in a different language and culture, suggesting that the CRs may be a constant feature of adult-child interaction.  相似文献   

14.
Two experiments were conducted to investigate functional similarities between “hunger CRs” of Konorski’s (1967) model of appetitive classical conditioning and sign-tracking behavior in rats. Konorski’s model predicts that hunger CRs will be facilitated (1) when a nonrein-forced stimulus similar to the reinforced CS is introduced, and (2) when some CS presentations are unexpectedly nonreinforced. In Experiment 1, hungry rats acquired a leverpress response to a retractable lever that was paired with response-independent food. Following this training, a second lever was introduced whose presentation was not followed by food. The effect of the presence of this second lever was to facilitate responding to the original lever. In Experiment 2, single-lever autoshaping training was followed by a shift from 100% pairing of the lever with food to only 50% of the lever presentations being followed by food. The introduction of partial reinforcement produced an immediate and durable increase in leverpressing. The findings of both experiments are consistent with predictions from Konorski’s model of classical conditioning if sign-tracking is considered as a “hunger CR.”  相似文献   

15.
Virtually no evidence of excitatory CR acquisition is observed in rabbit eyelid conditioning with a trace-conditioning procedure if the CS-UCS trace interval is greater than a few seconds. The lack of overt CRs following training with a trace-conditioning procedure has traditionally been interpreted as due to the passive decay of the CS stimulus trace over time. However, it is conceivable that a trace interval sufficiently long to preclude CR acquisition may be sufficiently long to teach the subject that the CS signals a UCS-free period, thereby producing an inhibitory CS. To test this proposal, eyelid conditioning in rabbits was conducted in two experiments with a 10-sec trace interval (there being no evidence of excitatory conditioning with this procedure). The trace-CS was then tested for evidence of inhibition with retardation-of-acquisition and summation tests. The trace-CS was shown to have conditional inhibitory properties. These results indicate that the interstimulus interval function in trace conditioning may be determined, in part, by inhibitory associations.  相似文献   

16.
This article introduces a new "real-time" model of classical conditioning that combines attentional, associative, and "flexible" configural mechanisms. In the model, attention to both conditioned (CS) and configural (CN) stimuli are modulated by the novelty detected in the environment. Novelty increases with the unpredicted presence or absence of any CS, unconditioned stimulus (US), or context. Attention regulates the magnitude of the associations CSs and CNs form with other CSs and the US. We incorporate a flexible configural mechanism in which attention to the CN stimuli increases only after the model has unsuccessfully attempted learn input-output combinations with CS-US associations. That is, CSs become associated with the US and other CSs on fewer trials than they do CNs. Because the CSs activate the CNs through unmodifiable connections, a CS can become directly and indirectly (through the CN) associated with the US or other CSs. In order to simulate timing processes, we simply assume that a CS is formed by a temporal spectrum of short-duration CSs that are activated by the nominal CS trace. The model accurately describes 94?% of the basic properties of classical conditioning, using fixed model parameters and simulation values in all simulations.  相似文献   

17.
Conditioning theories and recent real-time models commonly postulate that a reinforcer is signaled by a series of stimuli. In both Pavlovian and operant procedures, serial stimuli have been shown to control the likelihood and timing of responses over intervals of seconds and minutes. The present experiments were conducted to determine whether serial stimuli exercise similar effects over stimulus-reinforcer intervals in the order of hundreds of milliseconds. Such intervals typify those used in conditioning of the rabbit nictitating membrane response. A sequence of four tone pulses (50–100 msec) was used as the CS to assess the effectiveness of serial stimuli. After training with this CS, tests were conducted in which one or more of the pulses were removed. These perturbations of the sequence of stimuli over a 400-msec interval produced large deficits in CR likelihood and smaller alterations in CR timing. The results are discussed with respect to their implications for current real-time models of conditioning, and particularly with respect to their assumptions about the source of internal stimuli, rules for learning, and rules for generating CRs.  相似文献   

18.
Retarded conditioned response (CR) acquisition produced by unconditioned stimulus (US) preexposures has been attributed either to interference resulting from contextual conditioning or to habituation of the US. Both perspectives assume that the amount of retardation is directly related to the number of US preexposures. This assumption was examined in two experiments. In Experiment 1, separate groups of rabbits received 200 paraorbital shock US preexposures either in one session or spread equally over 10 daily sessions. Subsequently, all subjects received 150 CS-US pairings. Acquisition of nictitating membrane CRs was retarded relative to a naive control group only in the group that received the preexposures over 10 sessions. Thus, the number of US preexposure sessions, rather than the number of US preexposures, determined whether or not retarded acquisition was observed. In Experiment 2, four groups of rabbits received 1, 5, 20, or 40 shock US preexposures in each of 10 sessions. Over the subsequent 150 CS-US pairings, similar levels of retarded CR acquisition were observed in groups that received 20 and 40 US preexposures per session, a weak retardation effect was observed with 5 preexposures per session, and no retardation was observed with 1 preexposure per session. Thus, Experiment 2 suggested that retarded CR development was not greatly influenced by increasing the number of US preexposures above some minimum threshold number of exposures per session. Implications for current theories were discussed.  相似文献   

19.
The present experiments examined transfer of training from visual to auditory sensory modalities in classical conditioning of the rabbit’s nictitating membrane response. Experiment 1 examined transfer from initial training with a single visual CS to subsequent auditory discrimination training, and Experiment 2 examined transfer from visual discrimination training to auditory discrimination training. The major findings were that (1) initial conditioning of a visual CS facilitated the overall rate of CR acquisition to the auditory CSs separate from the requirements for discrimination learning (Experiments 1 and 2), and (2) initial visual discrimination training facilitated auditory discrimination learning (Experiment 2). Thus, the animals appeared to encode separately both contiguous CS-US relations and CS+ versus CS? relations during initial visual training. The results are discussed with respect to theories of extradimensional transfer.  相似文献   

20.
Two studies used a one-trial-a-day aversive conditioning procedure with rats as subjects to investigate the effects of a noise versus a light CS on conditioned freezing. Experiment 1 demonstrated that less conditioned freezing was elicited by the light, although the two CSs led to similar levels of freezing to the contextual cues of the conditioning chamber. Experiment 2 replicated these outcomes and showed that the manipulation of CS intensity produced results similar to those of modality, with the more intense CSs eliciting less freezing. The second experiment also determined that freezing to contextual cues resulted from context conditioning. According to the Rescorla-Wagner model, CSs that condition poorly should generate little competition with context conditioning. Since neither the modality nor intensity factor reliably influenced context conditioning, as measured by context-evoked freezing, the studies provide no support for the view that the effects on CS-evoked freezing represent differences in the strength of conditioning to the various stimuli. This finding raises the possibility that all of the CSs conditioned well but varied in their abilities to elicit freezing because they differed in terms of the form of defensive behavior under their control.  相似文献   

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