Classical conditioning of proboscis extension in honeybees (Apis mellifera).

Conditioned extension of the proboscis in restrained honeybees with odor as the CS and sucrose solution—delivered to the antenna (to elicit extension of the proboscis) and then to the proboscis itself—as the UCS. In a 1st series of experiments, acquisition was found to be rapid, both in massed and in spaced trials; its associative basis was established by differential conditioning and by an explicitly unpaired control procedure. Both extinction and spontaneous recovery in massed trials were demonstrated. In experiments on the nature of the UCS, eliminating the proboscis component lowered the asymptotic level of performance, whereas eliminating the antennal component was without effect; reducing the concentration of sucrose from 20% to 7% slowed acquisition but did not lower the asymptotic level of performance; and second-order conditioning was demonstrated. In experiments on the role of the UCS, an omission contingency designed to eliminate adventitious response-reinforcer contiguity was found to have no adverse effect on acquisition. In experiments designed to analyze the resistance to acquisition found after explicitly unpaired training in the 1st experiments, no significant effect was found of prior exposure either to the CS alone or to the UCS alone, although the unpaired procedure again produced resistance that was shown to be due to inhibition rather than to inattention; extinction after paired training was found to be facilitated by unpaired presentations of the UCS. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Acquisition of conditioned associations in Hermissenda: Additive effects of contiguity and the forward interstimulus interval.

Examined conditioned suppression of photokinesis (CSPK) by the marine mollusc in 3 experiments. In each experiment, groups of Ss received light (conditioned stimulus, CS) paired with high-speed orbital rotation (unconditioned stimulus, UCS), light and rotation explicitly unpaired, or no exposure to these stimuli. 24 hrs after training, all Ss were tested for CSPK in the presence of the light. 50 CS–UCS pairings resulted in a marginal CSPK, whereas 100 and 150 pairings produced strong CSPK. In Exp 2, delay between CS onset and UCS onset was varied between 1 and 10 s. The 10-s interstimulus interval (ISI) did not support conditioning, whereas 1-s and 2-s ISIs were effective. In Exp 3, CS–UCS pairings in which the CS preceded the onset of the UCS and ended with the offset of the UCS evoked stronger CSPK than either a CS that preceded the UCS and ended with its onset or a CS that was paired in simultaneous compound with the UCS. CS–UCS contiguity and the forward ISI act additively to establish the CS–UCS association. No differences were observed between groups that were untreated and that received the CS and UCS unpaired. Similarities are noted in the temporal characteristics of associative learning in these Ss and vertebrate species. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

NMDA receptor antagonist MK-801 blocks learning of conditioned stimulus-unconditioned stimulus contiguity but not fear of conditioned stimulus in goldfish (Carassius auratus L.).

The blockade of learning of Pavlovian fear conditioning by the N-methyl-D-aspartic acid (NMDA)-receptor antagonist MK-801 was examined in 166 goldfish. In previously untrained fish, MK-801 blocked learning of a light-off or a tone conditioned stimulus (CS) paired with an electrical shock unconditioned stimulus (UCS). Pretraining on the light-off CS did not affect the rate of learning of the tone CS but protected the tone learning from disruption by MK-801. Switching from the light-off to the tone CS changed the identity of the CS but not its temporal contiguity with the UCS. Pretraining consisting of pseudoconditioning of the light-off CS did not protect subsequent tone learning from blockade by MK-801. Thus, the NMDA receptor functions are necessary for learning related to the temporal contiguity of the CS and UCS but not to the identity of the CS as a cue to the occurrence of the fearful effects of the UCS. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Role of context in autoshaping.

Three experiments used an autoshaping procedure in 64 female White Carneaux pigeons to investigate the conditioning of the context and of a discrete CS with a food UCS. CS–UCS associations were measured by directed pecking at the key light CS; context–UCS associations were assessed by general activity in the context. Exp I investigated the influence of context–UCS associations on performance to a previously trained CS. The same CS produced greater keypecking in a context of higher associative strength. Exp II examined the influence of context–UCS associations on learning of CS–UCS associations. When tested in a context of fixed associative strength, a CS that had been trained in a context of high associative strength elicited less responding than one trained in a context of low associative strength. Exp III found that signaling a UCS by a discrete CS interfered with the formation of context–UCS associations, as measured both in terms of general activity and ability to promote responding to another CS. Results suggest that the context and the CS compete for association with the UCS. They also suggest that context–UCS associations facilitate the exhibition of CS–UCS associations. (17 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of contingency violations on the extinction of a conditioned fear inhibitor and a conditioned fear excitor.

In 4 experiments, 192 male Holtzman and Sprague-Dawley rats were used in a conditioned-suppression paradigm to assess the effects of contingency variations on responding to a conditioned stimulus (CS) inhibitor (CS–) and a conditioned stimulus excitor (CS+). In Exp I, various unconditioned stimulus/stimuli (UCS) frequencies were equated across the presence and absence of a CS– in the context of either background cues (continuous-trial procedure) or an explicit neutral event (discrete-trial procedure). With both procedures, a CS-alone treatment enhanced inhibition, whereas treatments involving 50 or 100% reinforcement for the CS– eliminated inhibition without conditioning excitation to that CS. The latter outcome also occurred in Exp II, with discrete-trial training equating considerably reduced UCS frequencies for the presence and absence of the CS–. In further evidence that inhibition was eliminated without conditioning excitation to the CS–, Exp III showed that a novel CS did not acquire excitation when 25, 50, or 100% reinforcement was equated across the presence and absence of that CS in the context of a discrete-trial event. Using the procedures of Exp I, Exp IV showed that a CS+ was extinguished by a CS-alone treatment but was substantially maintained by treatments involving 50 or 100% uncorrelated reinforcement. These effects for a CS+ and a CS– implicate CS–UCS contiguity, rather than contingency, as the factor determining the extinction of a CS. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Bridging temporal gaps between CS and US in autoshaping: Insertion of other stimuli before, during, and after CS.

In 4 experiments, female White Carneaux pigeons were exposed to key-light illuminations separated from food delivery by 12–60 sec. Approach to the key light did not develop on conventional trace-conditioning arrangements but occurred consistently whenever some auditory or visual stimulus filled the CS–UCS gap (serial conditioning) or was always present except during the gap. The CS approach was strong only when the stimulus present during the intertrial interval remained on until the termination of CS; if the stimulus ended at CS onset, conditioning did not occur. Although discriminability of CS–UCS gaps from intertrial periods seemed necessary for conditioning to occur in the absence of close CS–UCS contiguity, the outcome of the final experiment indicates that such discriminability was not sufficient for conditioning. Results are discussed in terms of possible 2nd-order conditioning effects and the changes in the associative strength of the "local context" existing when the CS appears, which may lead to superconditioning of CS. (35 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Conditioning the unconditioned response: Modification of the rabbit's (Oryctolagus cuniculus) unconditioned nictitating membrane response.

Conditioning-specific reflex modification (CRM) occurs when classical conditioning modifies responding to a unconditioned stimulus/stimuli (UCS) in the absence of a conditioned stimulus (CS). Three experiments monitored rabbit (Oryctolagus cuniculus) nictitating membrane unconditioned responses to 5 intensities and 4 durations of periorbital electrical stimulation before and after CS or UCS manipulation. CRM occurred after 12 days of CS-UCS pairings but not following unpaired CS/UCS presentations or restraint. CRM survived CS-alone and CS/UCS-unpaired extinction of the conditioned response (CR) but not presentations of the UCS alone, although CRs remained intact. Thus, CRs could be weakened without eliminating CRM and CRM could be weakened without eliminating CRs. Data indicate CRM is a reliable, associative effect that is more than a generalized CR and may not be explained by habituation, stimulus generalization, contextual conditioning, or bidirectional conditioning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Aversive second-order conditioning in the pigeon: Elimination of conditioning to CS1 and effects on established second-order conditioning.

After aversive 2nd-order conditioning was established in groups of female White Carneaux pigeons, conditioning to the 1st-order CS was eliminated by either nonreinforced presentations of CS or truly random presentations CS 1 and UCS. Subsequent testing of CS 2 revealed that nonreinforced CS presentations significantly reduced previously established 2nd-order conditioning, but truly random presentations of CS 1 and UCS did not. Data suggest that an association between the CS 2 memory and UCS memory was formed during 2nd-order conditioning. Results do not support conclusions drawn from previous research that indicated that rats form a direct association between CS 2 memory and CR in both appetitive and aversive 2nd-order conditioning preparations and that pigeons form an association between CS 2 and CS 1 memories in a 2nd-order autoshaping preparation. (French abstract) (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Associative and nonassociative theories of the UCS preexposure phenomenon: Implications for Pavlovian conditioning.

Excitatory Pavlovian conditioning of a discrete CS is attenuated by prior exposure to the UCS. The UCS preexposure phenomenon is observed in a variety of Pavlovian conditioning procedures as diverse as eyelid conditioning, the conditioned emotional response, and conditioned taste aversion learning. This article discusses the variables that affect the UCS preexposure phenomenon and uses this information in evaluating both associative and nonassociative accounts of the phenomenon. At least one associative account, based on context blocking, and at least one nonassociative account, based on central habituation of the emotional response to the UCS, remain viable. (71 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Evaluative conditioning in the picture–picture paradigm with random assignment of conditioned stimuli to unconditioned stimuli.

Human participants were allocated to 1 of 3 groups. In the conditioning group, each conditioned stimulus (CS)–unconditioned stimulus (UCS) pair was presented 7 times during the acquisition phase. Participants who were assigned to the extinction group saw 5 additional presentations of each CS in isolation after the 7 presentations of each CS–UCS pair. In the latent inhibition group, the CS-only trials were presented before the CS–UCS trials. Overall, a significant evaluative conditioning effect was observed. This effect cannot be dismissed on the basis of the arguments developed by A. P. Field and G. C. L. Davey (see records 1997-42912-009, 1998-11983-008, and 1999-10526-006), and the results thus provide strong evidence for the associative nature of evaluative conditioning. The results are also in line with other findings, which showed that evaluative conditioning is resistant to extinction. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Arousal-related associative response characteristics of dorsal lateral geniculate nucleus neurons during acoustic Pavlovian fear conditioning.

This research determined whether fear-conditioned, acoustic stimuli induce thalamic arousal reflected in associative responses in dorsal lateral geniculate nucleus (dLGN) neurons. Rabbits received a Pavlovian discriminative fear conditioning procedure in which one tone conditioned stimulus (CS+) was always paired with an aversive unconditioned stimulus (UCS) and another tone (CS–) was never paired with the UCS. Responses of single dLGN neurons to random CS+ and CS– presentations were then recorded. Nine of 15 recorded neurons demonstrated significantly greater firing during the CS+ versus the CS–. Their spontaneous activity demonstrated tonic firing during increased neocortical arousal and burst firing during decreased neocortical arousal. The results demonstrate that dLGN neurons show associative responses to fear-conditioned, acoustic stimuli and present a model for investigating the neural circuits by which such stimuli affect sensory processing at the thalamic level. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Blocking during serial feature-positive discriminations: Associative versus occasion-setting functions.

Previous work indicates that during serial feature-positive discriminations (i.e., feature–trace interval/common element/food presentations and separate nonreinforced common element presentations) the feature (A) acquires an association with food (unconditioned stimulus [UCS]) and also a capacity to modulate the common element (X)–UCS relation, which has been termed occasion setting (OS). In the present 2 experiments with 32 male Sprague-Dawley rats, a blocking design, serial feature-positive discrimination procedures, and a behavioral observation technique were used to assess the relation between associative and OS functions acquired by stimuli. In Exp I, prior conditioning of associative and OS functions to A blocked acquisition of both stimulus functions by a novel stimulus (B) trained in compound with A. In Exp II, prior acquisition of an A–UCS association blocked acquisition of a B–UCS association but had no effect on acquisition of B's OS function. These outcomes are discussed (a) as indicating that associative and OS functions are independent and may be based on separate learning processes, (b) as extending the known conditions for acquisitions of OS, and (c) with regard to the theoretical implications of assuming independence of associative OS functions acquired by stimuli. (28 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Simultaneous and backward fear conditioning in the rat.

Examined simultaneous and backward Pavlovian conditioning paradigms using a UCS event which was longer in duration than the CS. 3 experiments with male Sprague-Dawley rats (N = 96) paired a 4-sec electric shock with a 2-sec tone-light stimulus under conditions in which the onset of the stimulus occurred 0, .25, 1.0, 2.0, 4.0, or 4.5 sec. after the onset of the shock. Relative to nonpaired control procedures, response-contingent presentations of the CSs in these paradigms significantly suppressed a food-rewarded free operant, indicating that these temporal relationships can produce excitatory associative conditioning. It is suggested that the distinctions between "forward," "simultaneous," and "backward" procedures be modified to include a more molecular analysis of the UCS event. (21 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Conditioned diminution of the unconditioned skin conductance response.

During Pavlovian conditioning the expression of a conditioned response typically serves as evidence that an association between a conditioned stimulus (CS) and an unconditioned stimulus (UCS) has been learned. However, learning-related changes in the unconditioned response (UCR) produced by a predictable UCS can also develop. In the present study, we investigated learning-related reductions in the magnitude of the unconditioned skin conductance response (SCR). Healthy volunteers participated in a differential conditioning study in which one tone (CS+) was paired with a loud white-noise UCS and a second tone (CS?) was presented alone. In addition, probe trials that consisted of UCS presentations paired with the CS+ (CS + UCS) and CS? (CS ? UCS), as well as presentations of the UCS alone were included to assess UCR diminution. SCR and participants' expectations of UCS presentation were monitored during conditioning. Greater diminution of the UCR was observed to the UCS when it followed the CS+ compared to when it followed the CS? or was presented alone. Further, UCR amplitude showed an inverse relationship with the participants' ratings of UCS expectancy. However, conditioned UCR diminution was also observed independent of differential UCS expectancies. Our findings demonstrate conditioned diminution of the unconditioned SCR. Further, these findings suggest that although UCR amplitude is modified by conscious expectations of the UCS, conditioned diminution of the UCR can be expressed independent of learning-related changes in these expectations. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Reevaluating evaluative conditioning: A nonassociative explanation of conditioning effects in the visual evaluative conditioning paradigm.

In 2 studies, the authors investigated whether evaluative conditioning (EC) is an associative phenomenon. Experiment 1 compared a standard EC paradigm with nonpaired and no-treatment control conditions. EC effects were obtained only when the conditioned stimulus (CS) and unconditioned stimulus (UCS) were rated as perceptually similar. However, similar EC effects were obtained in both control groups. An earlier failure to obtain EC effects was reanalyzed in Experiment 2. Conditioning-like effects were found when comparing a CS with the most perceptually similar UCSs used in the procedure but not when analyzing a CS rating with respect to the UCS with which it was paired during conditioning. The implications are that EC effects found in many studies are not due to associative learning and that the special characteristics of EC (conditioning without awareness and resistance to extinction) are probably nonassociative artifacts of the EC paradigm. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Conditioning the rabbit's (Oryctolagus cuniculus) jaw-movement response: US magnitude effects on URs, CRs, and pseudo-CRs.

Describes an experiment in which 72 albino rabbits received (a) 45 daily acquisition sessions of single intraoral UCS presentations of 1, 5, or 20 cc. water, paired or unpaired with the CS (an 80 db. tone); and (b) 40 daily extinction sessions of single CS presentations. Results show that sinusoidal jaw movement (UR) rate following UCS offset (reflex afterdischarge) was an increasing function of UCS magnitude and acquisition sessions. Percentage CRs (paired with the CS) and pseudo-CRs (unpaired with the CS) were positively related to UCS magnitude, with paired-group performance consistently superior to that of corresponding unpaired controls. CR amplitude increased over acquisition sessions, while pseudo-CR amplitude remained uniformly low. UCR, CR, and pseudo-CR latencies decreased over acquisition. Frequencies of CRs and UCRs provided partial support for the consummatory response hypothesis, while the pseudo-CR frequencies cannot be completely accounted for by present theoretical formulations. (17 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Importance of relative temporal parameters in trace autoshaping: From excitation to inhibition.

Studied the role of the relative durations of CS–UCS gap and intertrial interval (ITI) in 2 autotracing experiments. In Exp I, CS–UCS gap duration was held constant at 12 sec, and the ITI was systematically varied between 15 and 240 sec across 5 groups of 6 female White Carneaux pigeons. Conditioned excitation (CS-approach) emerged at ITIs of greater than 60 sec, and conditioned inhibition (CS-withdrawal) emerged at ITIs of less than 60 sec. In Exp II, with 50 Ss, the time between successive UCSs averaged 87 sec, and the duration of the CS–UCS gap varied from 6 to 72 sec. CS-approach was observed only in the 6-sec gap condition, and CS-withdrawal developed with gaps of 24 sec or more. Findings indicate that the relative durations of CS–UCS gap and the ITI are more important than is the absolute degree of CS–UCS contiguity in determining whether and what type of conditioning occurs on trace arrangements. (35 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mechanisms underlying retarded emergence of conditioned responding following inhibitory training: Evidence for the comparator hypothesis.

The comparator hypothesis posits that conditioned responding is determined by a comparison at the time of testing between the associative strengths of the conditioned stimulus/stimuli (CS) and stimuli proximal to the CS at the time of conditioning. The hypothesis treats all associations as being excitatory and treats conditioned inhibition as the behavioral consequence of a CS that is less excitatory than its comparator stimuli. Conditioned lick suppression by rats was used to differentiate 4 possible sources of retarded responding to an inhibitory CS. These include habituation to the unconditioned stimulus/stimuli (UCS), latent inhibition to the CS, blocking of the CS-UCS association by the conditioning context, and enhanced excitatory associations to the comparator stimuli. Prior research has demonstrated the 1st 3 phenomena. Therefore, we employed parameters expected to highlight the 4th one—the comparator process. In Exp I, our negative contingency training produced a conditioned inhibitor that passed inhibitory summation and retardation tests. In Exp II we found transfer of retardation from an inhibitory CS to a novel stimulus when the location where retardation-test training occurred was excitatory. In Exp III, extinction of the conditioning context attenuated retardation regardless of whether extinction occurred before or after the CS-UCS pairings of the retardation test. Exp IV demonstrated that habituation to the UCS did not contribute to retardation in the present case. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Associative regulation of Pavlovian fear conditioning: Unconditioned stimulus intensity, incentive shifts, and latent inhibition.

Conditional stimuli (CS) associated with painful unconditional stimuli (UCS) produce a naloxone-reversible analgesia. The analgesia serves as a negative-feedback regulation of fear conditioning that can account for the impact of UCS intensity and CS predictiveness on Pavlovian fear conditioning. In Exp 1, training under naloxone produced learning curves that approached the same high asymptote despite UCS intensity. Shifting drug treatment during acquisition had effects that paralleled UCS intensity shifts. In Exp 3, naloxone reversed Hall-Pearce (1979) negative transfer using a contextual CS, indicating that conditional analgesia acquired during the CS–weak-footshock phase retards acquisition in the CS–strong-footshock phase. Exp 5 used a tone CS in both a latent-inhibition and a negative-transfer procedure. Only negative transfer was blocked by naloxone. Therefore, negative transfer but not latent inhibition is mediated by a reduction of UCS processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Contingency learning and causal detection in Hermissenda: I. Behavior.

The addition of extra light-alone or rotation-alone presentations to sequences of light-rotation pairings reduced the associative suppression of phototaxic behavior for the nudibranch Hermissenda. Training-induced changes in Type B photoreceptor light responses were found to parallel the training-induced behavioral changes in the intact animal. The decremental effects of the degraded contingency treatments upon neural and behavioral changes normally occasioned by light-rotation pairings reflected two processes. One factor was the increased stimulation frequency entailed by degraded contingency training. The second factor reflected the specifically unpaired character of the added light-alone or rotation-alone presentations, independent of frequency changes. The attenuation of phototaxic suppression was not because of a general habituation process or adaptation to the effects of either visual or vestibular stimulation. Instead, attenuation seemed to reflect a local interference effect of interspersed unpaired stimuli. The present experiments demonstrate a sensitivity to stimulus contingencies for Hermissenda similar to that of many vertebrates and indicate that contiguity and contingency relations are both encoded and stored in the Type B photoreceptors. The results indicate that similar neurophysiological mechanisms are involved. (PsycINFO Database Record (c) 2010 APA, all rights reserved)