Simple determination of urinary aldosterone without chromatography]

Previously acquired continuous avoidance performance of pigs in a shuttle-box was modified by a Pavlovian fear-conditioning procedure. Diazepam (1 mg/kg) given before the Pavlovian conditioning session prevented the increase in corticosteroids and the impairment of performance in the subsequent test session before the presentation of the fear signal. Diazepam given before the Pavlovian conditioning session and/or the test session did not prevent the increase of response to the CS presentation; however, the temporal pattern of increase differed according to the drug condition: the diazepam treatment on the day of the test significantly delayed the peak of responding to the CS; in pigs treated with diazepam on the day of Pavlovian conditioning and with saline on the day of test, the increase of response was diffuse instead of being localized to the CS presentation period. Pigs treated with diazepam both during learning and performance of fear conditioning showed some evidence of performance facilitation. Usual unitary interpretations cannot account for such results which would appear to be the net result of several intermingled effects among which state-dependent learning, acquisition deficit, and performance facilitation seem to be of importance.     

Real-time dopamine efflux in the nucleus accumbens core during Pavlovian conditioning.

To assess the role of dopamine input to the nucleus accumbens core in anticipatory learning, fast-scan cyclic voltammetry was combined with appetitive Pavlovian conditioning. One group of rats (Paired) received 16 tone-food pairings for at least four daily sessions while the control group (Unpaired) received the same number of unpaired tone and food presentations. Both groups showed transient dopamine responses during food presentation throughout training, confirming dopamine involvement in reward processing. Only the Paired Group, however, showed consistently timed dopamine transients during the 10-s tone presentation. Transients first appeared near the end of the tone period as each animal acquired the tone-food association and then occurred progressively sooner on subsequent sessions. Later sessions also revealed a consistently timed dopamine response soon after food delivery in Paired animals. Collectively, these results implicate phasic dopamine release in the acquisition of Pavlovian learning and also suggest an early dopamine response to the unconditioned stimulus as training continues. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The biological function of Pavlovian conditioning: The best defense is a good offense.

Signaled presentations of a rival male produce an aggressive CR in several species of fish. The present 2 experiments, with 16 male blue gouramies (Trichogaster trichopterus), showed that signaled territorial intrusion enables a male to defend his territory more aggressively than when the intruder is unsignaled. In Exp I, pairs of territorial males, with different conditioning histories, confronted one another for the 1st time. One member of the pair previously had received Pavlovian conditioning, whereas the other pair member had received explicitly unpaired presentations of the same signal (CS) and rival male (UCS). In the subsequent encounter, which was signaled by CS presentation, Pavlovian males delivered significantly more bites and tailbeatings than did their control group opponents. Exp II relied on a different control procedure, a UCS-only condition; however, again, Pavlovian males enjoyed a significant aggressive advantage. Results suggest an important ecological role for Pavlovian conditioning. (24 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Negative priming in associative learning: Evidence from a serial-conditioning procedure.

Three experiments investigated the suggestion that a predicted or primed stimulus commands less processing and consequently elicits a weaker CR than a stimulus that is not primed. In each experiment rats received initial training in which the presentation of each of 2 serial compounds, A-X and B-Y, was followed by the delivery of food. Subsequently, X's capacity to elicit the CR, approaching the site of food delivery, was assessed when X was preceded by Stimulus A (i.e., primed) or was presented after Stimulus B. Stimulus X elicited a more vigorous response when it was presented after B than when it followed A. These results show that the ability of one event to elicit its CR is reduced if its presentation has been predicted by some other event. This negative priming effect supports one aspect of A. R. Wagner's (1981) model of Pavlovian conditioning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dissociation of Pavlovian and instrumental incentive learning under dopamine antagonists.

The administration of the dopamine antagonists, pimozide and α-flupenthixol, to rats reduced Pavlovian–instrumental transfer when a conditioned stimulus (CS) that had been paired with a noncontingent food reward was tested on instrumental performance. The administration of the antagonists during Pavlovian conditioning and/or testing abolished the enhancement of instrumental performance by the CS. The effect of both antagonists on instrumental incentive learning was then examined. After training in which the rats performed 2 responses for different food rewards, they consumed 1 type food under the antagonists and the other type under vehicle during reexposure. When instrumental responding was subsequently tested in extinction, performance was unaffected by whether the rats had been reexposed to the training reward under the antagonists. These results suggest that Pavlovian and instrumental incentive learning are not mediated by a common process. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Deepened extinction from compound stimulus presentation.

Three experiments with rats and 2 with pigeons explored the effect of presenting 2 extinguished excitatory stimuli in compound. Four learning situations were used: Pavlovian magazine approach, Pavlovian fear conditioning, and instrumental discriminative instrumental learning in rats, as well as Pavlovian sign tracking in pigeons. All 5 experiments confirmed D. Reberg's (1972) observation that even after extinction of the individual stimuli, presenting them in compound evoked substantial responding. Moreover, nonreinforcement of that compound deepened extinction of an element more substantially than did additional presentation of that element alone. Such compound exposure reduced spontaneous recovery, reduced reinstatement, and slowed subsequent reconditioning. The primary determinant seemed to be the enhanced associative strength rather than the enhanced conditioned responding that occurred during the nonreinforced compound. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Latent inhibition in humans: Single-cue conditioning revisited.

Latent inhibition in human Pavlovian conditioning was assessed by way of autonomic responses. In Exp 1 (N?=?72), 3 pairs of conditioning and control groups were preexposed to 0, 10, or 20 to-be-conditioned stimuli (to-be-CSs), respectively. Acquistion of electrodermal 1st-interval and heart rate response conditioning were detectable only in the zero preexposure condition. However, 20 preexposures were needed for latent inhibition of vasomotor response conditioning. In Exp 2 (N?=?48), preexposure to the to-be-CS was compared with preexposure to a stimulus that was not presented during subsequent acquisition. CS preexposure completely abolished electrodermal 1st-interval and heart rate response conditioning. Although vasomotor conditioning was not affected by preexposure, latent inhibition of 2nd-interval electrodermal response conditioning was obtained. Taken together, the data from both experiments provide clear evidence for latent inhibition in human Pavlovian conditioning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Second-order conditioning with and without unconditioned stimulus presentation

The effects of presenting various episodes after serial presentation of two conditioned stimuli (CS2-CS1 sequences) on second-order conditioning to CS2 were examined in three experiments using rat subjects in an appetitive conditioning situation. In Experiment 1, presentation of food unconditioned stimuli (USs) immediately after CS2-CS1 sequences interfered with second-order conditioning of CS2. In Experiment 2, postsequence presentation of a "surprising" US interfered with second-order conditioning more than did presentation of an "expected" US; similarly, less second-order conditioning of CS2 was observed when postsequence nonpresentation of a US was surprising than when US omission was expected. In Experiment 3, the interfering effect of US presentation on second-order conditioning was smaller when a brief delay was introduced between presentation of the CS2-CS-1 sequence and the US. The results are discussed in terms of an information-processing theory recently proposed by Wagner and his colleagues.     

Differences in the sexual conditioned behavior of male and female Japanese quail (Coturnix japonica).

The conditioned responses of male and female Japanese quail (Coturnix japonica) were compared in a Pavlovian conditioning procedure in which presentation of a brief conditioned stimulus was immediately followed by the release of a copulation partner. Male quail vigorously approached the conditioned stimulus and were much more likely to enter the compartment housing their copulation partner than were female birds (Experiment 1). In females, sexual conditioning resulted in increased squatting (Experiment 2). This response was the reflection of sexual behavior rather than more general social behavior (Experiment 3). These findings provide the first definitive evidence of sexual learning in female quail and are consistent with the interpretation that sexual conditioning increases sexual arousal or receptivity in both sexes but the increase has different behavioral manifestations in male and female quail. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of D-cycloserine on the extinction of appetitive operant learning.

Four experiments with rat subjects examined whether D-cycloserine (DCS), a partial NMDA agonist, facilitates the extinction of operant lever-pressing reinforced by food. Previous research has demonstrated that DCS facilitates extinction learning with methods that involve Pavlovian extinction. In the current experiments, operant conditioning occurred in Context A, extinction in Context B, and then testing occurred in both the extinction and conditioning contexts. Experiments 1A and 1B tested the effects of three doses of DCS (5, 15, and 30 mg/kg) on the extinction of lever pressing trained as a free operant. Experiment 2 examined their effects when extinction of the free operant was conducted in the presence of nonresponse-contingent deliveries of the reinforcer (that theoretically reduced the role of generalization decrement in suppressing responding). Experiment 3 examined their effects on extinction of a discriminated operant, that is, one that had been reinforced in the presence of a discriminative stimulus, but not in its absence. A strong ABA renewal effect was observed in all four experiments during testing. However, despite the use of DCS doses and a drug administration procedure that facilitates the extinction of Pavlovian learning, there was no evidence in any experiment that DCS facilitated operant extinction learning assessed in either the extinction or the conditioning context. DCS may primarily facilitate learning processes that underlie Pavlovian, rather than purely operant, extinction. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Effects of ethanol on Pavlovian autoshaping in rats

Approach responses, consummatory behaviors, and directed motor responses maintained by food reward resemble autoshaping CRs and are increased by lower doses of ethanol. This study evaluated the effects of presession i.p. injections of ethanol doses (0.00, 0.25, 0.50, 0.70. or 1.00 g/kg) on the acquisition of lever-press autoshaping CR performance in groups of male Long-Evans hooded rats. Paired groups received 15 daily sessions of Pavlovian autoshaping procedures, wherein the insertion of a retractable lever for 5 s (CS) was followed by the response-independent presentation of food (US). Ethanol facilitated lever-press autoshaping CR acquisition, as revealed by dose-related increases in the number of trials on which CRs were performed. The form of the dose-effect curve was inverted U-shaped with maximal responding induced during sessions 1-5 by the 0.70 g/kg ethanol dose. A similar dose-effect curve was observed during sessions 11-15, revealing that the effects of ethanol on autoshaping CR performance were relatively stable. A pseudoconditioning control group injected presession with 0.50 g/kg ethanol received training wherein the food US was presented randomly with respect to the lever CS. Few lever-presses were performed by the Random 0.50 group, indicating that ethanol's effects on autoshaping CR acquisition and maintenance observed in the Paired 0.50 group were not due to its psychomotor activating effects. A non-injection control group performed more autoshaping CRs than did the control group injected presession with saline, indicating that daily presession i.p. injections per se suppress autoshaping CR performance. Results reveal that low doses of ethanol enhance Pavlovian conditioning of directed motor and consummatory-like responding maintained by food reward. Implications for autoshaping accounts of impulsivity and drug abuse are considered.     

Discriminative properties of morphine that modulate associations between tastes and lithium chloride.

Wistar rats learned to withhold consumption of a target solution when morphine preceded presentation of the target solution and lithium chloride (LiCl) and to consume the same target solution when saline preceded the presentation of the solution. After this serial feature discrimination training, morphine did not block the formation of a Pavlovian association between saccharin and LiCl but did suppress consumption of familiar tap water. After Pavlovian conditioning, morphine blocked the formation of an association between saccharin and LiCl but did not suppress consumption of a familiar tap water solution. The roles of morphine and saline can be interchanged. It appears that the morphine discriminative stimulus is calling up a representation of neither the conditioned stimulus nor the unconditioned stimulus alone, but rather a modified representation of some aspect of their association. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Evaluation of the relation between Pavlovian occasion-setting and instrumental discriminative stimuli: A blocking analysis.

Retracted October 1990. (See record 1991-03475-001.) Conducted 2 experiments with 72 male Sprague-Dawley rats, using a blocking design (A+, then AB+) to assess the relation between Pavlovian occasion-setting and instrumental discriminative stimuli. Prior conditioning of both associative and occasion-setting functions of A in a serial feature-positive procedure blocked acquisition of an instrumental discriminative function by a novel stimulus (B) trained in compound with A. Neither prior conditioning of only an A/unconditioned stimulus/stimuli (UCS) association nor prior conditioning of Stimulus A using a Pavlovian simultaneous feature-positive procedure, which does not endow A with an occasion-setting function, blocked acquisition of an instrumental discriminative function by B. Prior acquisition of an instrumental discriminative function by A blocked acquisition of a Pavlovian occasion-setting function by a novel stimulus (B) trained in compound with A but did not block acquisition of an association between B and the UCS. (39 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Relative validity of contextual and discrete cues.

Contextual conditioning during relative validity training was explored in 3 experiments that used an appetitive Pavlovian conditioning preparation with rats. Magazine entries were the conditioned response. In Experiment 1, true-discrimination (TD: AX+, BX–) training generated weaker conditioning of X than did pseudodiscrimination (PD: AX+/–, BX+/–) training. The context showed a similar relative validity effect. Also, both PD training and simple partial reinforcement (X+/–) reduced contextual conditioning more than did unsignaled food, a demonstration of relative validity using partial reinforcement. Experiments 2 and 3 used within-subject and between-subjects designs, respectively, and showed that relative validity was determined by the summation of differences in conditioning to both the common element (X) and the context. The results are consistent with an attentional model or with a computational comparator model but not with the Rescorla-Wagner (R. A. Rescorla & A. R. Wagner, 1972) model. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Facilitation of appetitive Pavlovian conditioning by d-amphetamine in the shell, but not the core, of the nucleus accumbens.

The effects of postsession d-amphetamine within subregions of the ventral and dorsal striatum on appetitive Pavlovian learning were assessed. Rats acquired a conditioned approach response on presentation of a stimulus predictive of 10% sucrose solution (unconditioned stimulus [US]), but not during equally frequent presentations of a stimulus uncorrelated with the US. In Experiment 1, postsession d-amphetarnine infusions enhanced acquisition of conditioned responding, with no effect on control measures. In Experiment 2, rats received postsession d-amphetamine in the accumbens shell or core. Shell infusions facilitated conditioning; core infusions did not. In Experiment 3, dorsomedial striatal infusions of d-amphetamine also were ineffective. In sum, dopaminergic activation within the shell, but not the core, of the nucleus accumbens facilitates the acquisition of a Pavlovian association. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Role of the anterior cingulate cortex in the control over behavior by Pavlovian conditioned stimuli in rats.

To investigate the contribution of the anterior cingulate cortex (ACC) to stimulus-reward learning, rats with lesions of peri- and postgenual ACC were tested on a variety of Pavlovian conditioning tasks. Lesioned rats learned to approach a food alcove during a stimulus predicting food, and responded normally for conditioned reinforcement. They also exhibited normal conditioned freezing and Pavlovian-instrumental transfer, yet were impaired at autoshaping. To resolve this apparent discrepancy, a further task was developed in which approach to the food alcove was under the control of 2 stimuli, only 1 of which was followed by reward. Lesioned rats were impaired, approaching during both stimuli. It is suggested that the ACC is not critical for stimulus-reward learning per se, but is required to discriminate multiple stimuli on the basis of their association with reward. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Associations between Pavlovian CSs and context.

Three experiments, with 48 female Carneaux pigeons, used autoshaping procedures to assess associations between Pavlovian CSs and the contexts in which they occur. Three contexts were identified by different visual wall patterns; conditioning of those contexts was assessed by the amount of general activity in their presence. Exp I found that key-light CSs given discriminative autoshaping with food in 1 context could differentially 2nd-order conditioned activity to 2 new contexts. Exp II used a sensory preconditioning procedure to detect associations between 2 contexts and neutral key lights given in their presence. When those key lights were differentially paired with food in a 3rd context, activity changed differentially in the original 2 contexts. Exp III found that if 2 key lights were paired with food in 2 different contexts, differential extinction of those key lights induced differential activity in their contexts. Consequently, CSs that are either previously conditioned, neutral, or currently undergoing conditioning all become associated with the context in which they appear. Exps II and III found that the changes in context value induced by manipulation of the key lights influenced learning and performance to other CSs. A context that was made valuable through manipulation of its CS was better able to block conditioning to another CS but also better able to promote performance to previously trained CSs. Results agree with outcomes of direct conditioning of a context by a UCS and suggest that CS-induced changes in context are quite powerful. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Associative structure of fear memory after basolateral amygdala lesions in rats.

The authors have recently demonstrated that rats with basolateral amygdala (BLA) lesions acquire Pavlovian fear conditioning after overtraining. However, it is not known whether the associative basis of Pavlovian fear memory acquired by rats with BLA lesions is similar to that of intact rats. Associations are typically formed between the conditional (CS) and unconditional (US) stimuli (stimulus-stimulus; S-S), although it is possible for stimuli to enter into association with the responses they produce (stimulus-response; S-R). Indeed, the central nucleus of the amygdala, which is essential for fear conditioning in rats with BLA lesions, may mediate S-R associations in some Pavlovian tasks. The authors therefore used a postconditioning US inflation procedure (i.e., exposure to intense footshock USs) to assess the contribution of S-S associations to fear conditioning after overtraining in rats with BLA lesions. In Experiment 1, intact rats that were overtrained and later inflated displayed elevated freezing levels when tested, indicating that S-S associations contribute to overtrained fear memories. Interestingly, neither neurotoxic BLA lesions nor temporary inactivation of the BLA during overtraining prevented the inflation effect (Experiment 2 and 3, respectively). These results reveal that S-S associations support Pavlovian fear memories after overtraining in both intact rats and rats with BLA lesions, and imply that the central nucleus of the amygdala encodes CS-US associations during fear conditioning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Anterograde amnesia for Pavlovian fear conditioning and the role of one trial overshadowing: Effects of preconditioning exposures to morphine in rat.

Four experiments studied anterograde deficits in Pavlovian fear conditioning following prolonged exposure to the μ-opioid receptor agonist morphine. Injections of morphine produced temporally graded anterograde amnesia characterized by deficits in contextual and conditioned-stimulus (CS) conditioning 1 or 7 days and selective impairment in CS conditioning 21 days after last injection. This anterograde deficit in conditioning did not recover across a retention interval, was absent when rats were tested immediately after conditioning, and required the presence of an auditory CS. These results suggest that anterograde deficits in Pavlovian fear conditioning emerged from differences in susceptibility to 1-trial overshadowing of context by CS. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Characterization of a fibrinogen-clotting enzyme from Trimeresurus stejnegeri venom, and comparative study with other venom proteases

It has been well documented that drug-associated cues are important for the development and expression of drug tolerance. The Pavlovian conditioning analysis of tolerance emphasizes the importance of a drug-associated cues to tolerance by equating a drug administration with a learning trial. According to this analysis, tolerance should be subject to external inhibition, the disruption of a conditional response by a novel stimulus. We previously reported that tolerance to the ataxic effect of ethanol was attenuated by a novel strobe/noise presentation (31). In this article we report evidence of a compensatory CR in rats tolerant to the ataxic effect of ethanol as tested on the tilting plane. Both the compensatory CR and tolerance were disrupted by the presentation of a novel strobe/noise stimulus providing converging evidence that the attenuation of tolerance by a novel stimulus results from external inhibition of Pavlovian conditioning. The disruption of ethanol tolerance and the conditional response mediating tolerance was also apparent when the novel omission of the strobe/noise stimulus was used as the external inhibitor in rats made tolerant to ethanol with the stimulus on. Finally, we have shown that the disruptive effect of a novel stimulus on ethanol tolerance is decreased when there is a 10-day delay between the final tolerance development session and testing, demonstrating that the interval between training and testing is important when assessing associative tolerance.