Latent timing in human conditioned avoidance.

Four experiments explored signal timing in human conditioned avoidance. Participants received discrimination training with different duration signals that announced the outcome (S+) or not (S-). Temporal discrimination and superposition of performance to S+ signals of different length (3, 6, or 9 s) was found both in within-subjects (Experiment 1a) and between-subjects (Experiment 1b) designs. S- signals also produced a temporal discrimination and superposition effect during a single test trial conducted after the meaning of the signals was reversed through instructions. Experiments 2a and 2b replicated these results in a situation in which (a) the durations of the S+ and S- signals were different (4.5 or 9 s) to prevent any temporal generalization between them (Experiment 2a), and (b) only S- signals were presented during training, precluding developing of inhibition to S- (Experiment 2b). These results show that participants time both S+ and S- signals in human conditioned avoidance, and they further suggest that the timing of a cue is independent of reinforcement. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The manipulation of dominance in monkeys with conditioned fear.

"2 group dominance tests were conducted on 10 rhesus monkeys. On the basis of these tests 5 pairs of animals adjacent, or nearly adjacent, in the hierarchy were given an additional 5 dominance determinations. The animal in each pair which received the greater number of raisins in each of the 7 tests between the 2 animals was designated as dominant. This animal in each pair was subjected to avoidance conditioning with this submissive partner as the conditioned stimulus… . The dominance status was found to be significantly reversed following the completion of conditioning. It was suggested that this observation provides behavioral evidence for the presence of fear in avoidance conditioning which is independent of the conditioning situation." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Extinction of a conditioned motor response following hypnosis.

The administration of a standard hypnosis induction procedure to 6 randomly assigned experimental Ss resulted in the disappearance of a recently acquired conditioned motor response. When hypnosis was terminated by another standard procedure the CR reappeared. On subsequent trials its appearance followed the usual extinction pattern. An equated control group (6 Ss) gave responses that followed the usual extinction pattern during both a extinction trials. Possible interpretations were considered and suggestions for further study made. (20 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of posttraining damage to the pedunculopontine tegmental nucleus on conditioned stimulus transfer in two-way active avoidance in rats.

The effects of posttraining excitotoxic lesions of the pedunculopontine tegmental nucleus (PPTg) on two-way active avoidance after changing the conditioned stimulus (CS) used during prelesion training were examined. Prelesion training was carried out with either a tone or a light as the CS, and this CS was changed during postlesion training. Replacing the tone with a light reduced the performance of control and lesioned rats, but the degree of reduction was higher in the latter. Replacing the light with a tone had slight detrimental effects in lesioned rats but not in controls. Thus, posttraining PPTg lesions slowed down the reacquisition of shuttle-box avoidance under conditions of CS transfer, an effect that may be attributable to disruption of attention and/or gating of sensory stimuli. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Conditioned nausea in rats: Assessment by conditioned disgust reactions, rather than conditioned taste avoidance.

The terms conditioned taste avoidance and conditioned taste aversion are often used interchangeably in the literature; however, considerable evidence indicates that they may represent different processes. Conditioned taste avoidance is measured by the amount that a rat drinks in a consumption test that includes both appetitive phases and consummatory phases of responding. However, conditioned taste aversion is more directly assessed using the taste reactivity (TR) test that includes only the consummatory phase of responding. Rats display a conditioned taste aversion as conditioned disgust reactions (gapes, chin rubs, and paw treads) during an intraoral infusion of a nausea-paired flavored solution. Only treatments that produce nausea produce conditioned disgust reactions, but even rewarding drugs produce conditioned taste avoidance. Furthermore, treatments that alleviate nausea prevent the establishment and the expression of conditioned disgust reactions, but they do not necessarily modify conditioned taste avoidance. Considerable evidence exists indicating that these two measures can be independent of one another. The potential of a compound to produce conditioned disgust reactions is a reflection of its nausea-inducing properties. Taste avoidance may be motivated by conditioned fear rather than conditioned nausea, but conditioned disgust is motivated by conditioned nausea. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Ontogeny of eyeblink conditioned response timing in rats.

Eyeblink conditioned response (CR) timing was assessed in adult and infant rats. In Experiment 1, adult rats were trained with a 150-ms tone conditioned stimulus (CS) paired with a periorbital shock unconditioned stimulus (US; presented at 200- or 500-ms interstimulus intervals [ISIs]). The rats acquired CRs with 2 distinct peaks that occurred just before the US onset times. Experiments 2 and 3 examined developmental changes in CR timing in pups trained on Postnatal Days 24-26 or 32-34. Experiment 3 used a delay conditioning procedure in which the tone CS continued throughout the ISIs. Pups of both ages exhibited robust conditioning. However, there were age-related increases in the percentage of double-peaked CRs and in CR timing precision. Ontogenetic changes in eyeblink CR timing may be related to developmental changes in cerebellar cortical or hippocampal function. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The ontogeny of interstimulus interval (ISI) discrimination of the conditioned eyeblink response in rats.

Discrimination of the eyeblink conditioned response (CR) between conditioned stimuli (CSs) of different durations and modalities was examined across development in rats. Interstimulus interval (ISI) discrimination was evident at Postnatal Days 23-34 in Experiment 1, and earlier CR peak latencies and enhanced CR amplitudes were seen to the long CS in the ISI discrimination group relative to a control group receiving the short CS without reinforcement. Experiment 2 showed that early CR peak latencies and enhanced CR amplitudes to the long CS in the ISI discrimination group were due to associative pairing of the short CS and unconditioned stimulus. Experiment 3 demonstrated ISI discrimination in adults that was improved relative to younger subjects, but with no enhancement of CR amplitude to the long CS in the ISI discrimination group. Cerebellar cortical maturation may influence the ontogeny of CR timing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Learning from others to cope with biting flies: Social learning of fear-induced conditioned analgesia and active avoidance.

Although fear conditioning has received extensive attention, little is known about the roles of social learning whereby an individual may learn and acquire the fear responses of another. The authors examined individually and socially mediated acquisition of fear and analgesia to the natural aversive stimulus of biting flies. Exposure to biting flies elicited in individual naive mice analgesia and active self-burying to avoid the flies. When exposed 24 hr later to flies whose biting parts were removed, but not to nonbiting house flies, these mice displayed conditioned analgesia and self-burying. This "one-trial" conditioned analgesia and avoidance was also acquired through social learning without direct individual experience with biting flies. Naive "observer" mice that witnessed other "demonstrator" mice being attacked by biting flies exhibited analgesia and self-burying 24 hr later to altered flies. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of a positive social reward upon a verbal avoidance response.

In investigating the effect of reward upon the acquisition and extinction of avoidance response, a word association task was presented to 90 Ss for 8 conditioning and 12 extinction trials. During conditioning, associations to preselected words were punished on Trial 1 and whenever S repeated them. There were 3 acquisition groups: 1 received the above training, the 2nd also received reward for substitute associations, and the 3rd obtained reward during the 2nd ? of acquisition only. Each acquisiton group was divided into 2 extinction subgroups: 1 received neither reward nor punishment while the 2nd was rewarded for avoiding. Results indicated that reward hastened acquisition and delayed extinction of avoidance responses, thus confirming hypotheses regarding the concept of secondary gain. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neuronal correlates of conditioned inhibition of the eyeblink response in the anterior interpositus nucleus.

Conditioned inhibition (CI) of the rat eyeblink response and the neuronal correlates of CI in the cerebellar interpositus nucleus were examined in the present study. In Experiment 1, CI was established with a novel, 3-group design. In Experiment 2, neuronal activity in the anterior interpositus nucleus was recorded during CI training and testing. Each rat was given 2 training phases and then tested for CI with summation and retardation tests. Rats given CI training showed behavioral inhibition compared with rats in 2 control groups. Neuronal activity in the anterior interpositus nucleus correlated with behavioral responding during discrimination training and during the summation test. The results suggest that neurons in the cerebellar anterior interpositus nucleus may participate in the acquisition or expression of CI. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effects of a monetary reward on the acquisition of an imitative response.

"The present study extends the results of an earlier investigation [see 34: 827]… . The findings of the previous study supported the hypothesis that" imitation or opposition was dependent not only on its probability of leading to reward "but also on the prevailing social sanctions for its use. In the present study it was hypothesized that the obtained attenuation of an instrumental imitation or opposition response under negative sanctions toward nonindependent behavior would be overcome by increasing the utility of achieving the task goal… . In general, opposition was more difficult to condition than imitation." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Characteristics of a conditioned response in human subjects during extinction trials following a single traumatic conditioning trial.

A single experience of respiratory paralysis can be used to establish a conditioned response (CR) to a hitherto neutral stimulus. Respiratory paralysis to those undergoing it is horrific but not painful. The CR does not extinguish but becomes stronger as time passes despite repeated extinction trials. The skeletal aspects of the response are more variable than the autonomic aspects and do not provide any constant stimulus input. The results do not fit an "anxiety-reduction" explanation for the inextinguishability of traumatically conditioned responses but suggest that these responses have characteristics not mediated by reinforcement. (20 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Medial dorsal thalamic lesions impair blocking and latent inhibition of the conditioned eyeblink response in rats.

The effects of lesions of the medial dorsal thalamic nucleus (MD) on blocking and latent inhibition (LI) of the rat eyeblink response were examined in the present study. Previous work has demonstrated that the cingulate cortex and related thalamic areas are involved in processing conditioning stimuli throughout training. The experiments in the present study tested the hypothesis that disruption of cingulothalamic stimulus processing produced by lesions of the MD would impair 2 types of associative learning that involve decremental changes in attention. In Experiment 1, MD lesions severely impaired blocking. In Experiment 2, NM lesions severely impaired LT. The results indicate that lesions of the NM impair incremental, decremental, or both types of changes in stimulus processing during learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effects of chlorpromazine on GSR conditioning.

Research had suggested that chlorpromazine reduces anxiety and, from another line of research, that there is a positive relationship between degree of anxiety and ease of conditioning. The present research aimed at an assessment of the combination of these findings, viz., if chlorpromazine reduces anxiety, and lowered anxiety (reduced drive) decreases the ease of obtaining a conditioned response, then GSR conditioning should decrease with patients taking chlorpromazine. The results were in the hypothesized direction. Dosage of chlorpromazine was related to decrease in conditioning ability, with a moderate dosage (275-410 mg. per day) most effective in making conditioning difficult. 15 refs. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Right-sided human prefrontal brain activation during acquisition of conditioned fear.

This H/21?O positron emission tomography (PET) study reports on relative regional cerebral blood flow (rCBF) alterations during fear conditioning in humans. In the PET scanner, subjects viewed a TV screen with either visual white noise or snake videotapes displayed alone, then with electric shocks, followed by final presentations of white noise and snakes. Autonomic nervous system responses confirmed fear conditioning only to snakes. To reveal neural activation during acquisition, while equating sensory stimulation, scans during snakes with shocks and white noise alone were contrasted against white noise with shocks and snakes alone. During acquisition, rCBF increased in the right medial frontal gyrus, supporting a role for the prefrontal cortex in fear conditioning to unmasked evolutionary fearrelevant stimuli. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dissociating the conditioning and the anorectic effects of estradiol in female rats.

The present series of experiments challenges the ability of the hormone estradiol to act as an unconditioned stimulus in the conditioned taste avoidance (CTA) learning paradigm. We hypothesize that reductions in sucrose consumption observed after pairing it with estradiol are not indicative of associative learning, but due to the unconditioned expression of estradiol’s anorectic effects during the time of CTA assessment. Three experiments in which a sucrose solution was paired with estradiol were conducted to test this hypothesis. Experiment 1 demonstrated that female rats expressed a reduction in post-pairing sucrose consumption even though the anorectic effects of estradiol had subsided. Experiment 2 showed that although a low dose of estradiol produced anorexia, it did not elicit post-pairing reductions in sucrose consumption. Experiment 3 revealed that contingent pairing was a requirement for post-pairing reduction in sucrose consumption even when testing was done at a time when anorexia is expressed. These findings demonstrate the dissociability of the conditioning and anorectic effects of estradiol, providing evidence against the hypothesis. The results are discussed in terms of independent neural mechanisms underlying the disparate behaviors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Time and stimulus specificity in extinction of the conditioned nictitating membrane response in the rabbit (Oryctolagus cuniculus).

The present experiments demonstrated that, in the rabbit nictitating membrane preparation, a conditioned response (CR) can be selectively eliminated in one portion of a conditioned stimulus (CS) while it is still paired with the unconditioned stimulus (US). Rabbits were initially trained with two stimuli (tone, light). Each was paired with the US by using a mixture of two CS-US interstimulus intervals (ISIs): 200 ms and 1,200 ms in Experiment 1; 150 ms and 500 ms in Experiment 2. The CRs showed double peaks, one for each ISI. Subsequently, one CS (A) was trained with only the longer ISI, whereas the other CS (B) continued to be trained with both ISIs. Consequently, the CR peak based on the shorter ISI disappeared for CSA but not for CSB. The later CR peaks during both CSA and CSB were maintained. These results support time-based models of conditioning. Implications for proposed mechanisms of extinction are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Modulation of the acquisition of the rabbit eyeblink conditioned response by conditioned contextual stimuli.

Three experiments were conducted to ask if conditioned emotional responses (CERs) controlled by contextual cues modulate the acquisition of eyelid conditioned responses (CRs) to discrete conditioned stimuli (CSs). Experiment 1 showed that 30-s auditory stimuli that were paired with aversive shocks to one paraorbital region or the other controlled discriminated CERs, as measured by potentiation of a startle response. In Experiments 2 and 3, similarly trained 30-s stimuli served as contexts in which 1,050-ms CSs were paired with a paraorbital unconditioned stimulus (US). Reinforced contexts both impaired (Experiments 2A and 2B) and facilitated (Experiment 3B) acquisition of the eyeblink CR, depending on the locus of the USs involved. The data are consistent with the interpretation that CERs controlled by contextual cues facilitate CR acquisition, but do so in the face of blocking effects of CR tendencies also conditioned to the contextual cues. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The acquisition of conditioned responding.

This report analyzes the acquisition of conditioned responses in rats trained in a magazine approach paradigm. Following the suggestion by Gallistel, Fairhurst, and Balsam (2004), Weibull functions were fitted to the trial-by-trial response rates of individual rats. These showed that the emergence of responding was often delayed, after which the response rate would increase relatively gradually across trials. The fit of the Weibull function to the behavioral data of each rat was equaled by that of a cumulative exponential function incorporating a response threshold. Thus, the growth in conditioning strength on each trial can be modeled by the derivative of the exponential—a difference term of the form used in many models of associative learning (e.g., Rescorla & Wagner, 1972). Further analyses, comparing the acquisition of responding with a continuously reinforced stimulus (CRf) and a partially reinforced stimulus (PRf), provided further evidence in support of the difference term. In conclusion, the results are consistent with conventional models that describe learning as the growth of associative strength, incremented on each trial by an error-correction process. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Incubation effect: Role of awareness in an immediate versus delayed test of conditioned emotionality.

"The purpose of the study was to test the view that conditioned emotionality, as measured by the GSR, increases after a delay and that this increase is greater when the subject is aware of the relation between the CS and UCS. Certain words were associated with shock. The subject was aware of the relation between one word and shock but was unaware of the relation between a second word and shock. The GSR to these words was compared to the GSR to a word not associated with shock." The results confirmed the hypothesis. (PsycINFO Database Record (c) 2010 APA, all rights reserved)