Releaser-induced recognition learning.

A variant of Pavlovian conditioning, termed the releaser-induced recognition-learning model, is introduced, described, and evaluated for generality and efficacy in accounting for learning phenomena. Elements of the innate releasing mechanism of classical ethology are combined in the model with the transfer-of-control version of Pavlovian stimulus substitution. The resulting mechanism, assumed to underlie simple recognition learning, essentially appears to induce a transfer between stimuli of control over the release of preorganized responses. Another proposition of the model concerns the relative taxic direction of originally released and redirected responses. The hypothesis that stimulus relationships other than temporal predictiveness can produce learned behavior is also considered. The proposed model provides a unitary account of recognition learning that includes imprinting and social learning as well as Pavlovian conditioning and some forms of instrumental conditioning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differential effects of adding and removing components of a context on the generalization of conditional freezing.

Rats were conditioned across 2 consecutive days where a single unsignaled footshock was presented in the presence of specific contextual cues. Rats were tested with contexts that had additional stimulus components either added or subtracted. Using freezing as a measure of conditioning, removal but not addition of a cue from the training context produced significant generalization decrement. The results are discussed in relation to the R. A. Rescorla and A. R. Wagner (1972), J. M. Pearce (1994), and A. R. Wagner and S, E. Brandon (2001) accounts of generalization. Although the present data are most consistent with elemental models such as Rescorla and Wagner, a slight modification of the Wagner-Brandon replaced-elements model that can account for differences in the pattern of generalization obtained with contexts and discrete conditional stimuli is proposed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Pavlovian Conditioning: The CS-UR Relation.

A new Pavlovian procedure used fluid-elicited throat-movement responses of the pigeon (N=66) to study the effects on conditioning of the temporal relation of the conditioned stimulus (CS) to the unconditioned stimulus-unconditioned response (US-UR). Because the throat-movement response has a substantial latency and duration, the relation of the CS to the US and UR could be independently evaluated. Four experiments indicated that, operationally, the relation of the CS to the UR--not to the US--is critical for conditioning in this preparation. The conventional emphasis on CS-US relations is based on procedures that confound the occurrence of the US with the UR and that foster generalization decrement between training and testing. The authors indicate how several conditioning phenomena may be reinterpreted in terms of CS-UR relations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Amygdalar unit activity during three learning tasks: Eyeblink classical conditioning, Pavlovian fear conditioning, and signaled avoidance conditioning.

Neural activity in central and basolateral amygdala nuclei (CeA and BLA, respectively) was recorded during delay eyeblink conditioning, Pavlovian fear conditioning, and signaled barpress avoidance. During paired training, the CeA exhibited robust learning-related excitatory activity during all 3 tasks. By contrast, the BLA exhibited minimal activity during eyeblink conditioning, while demonstrating pronounced increases in learning-related excitatory responsiveness during fear conditioning and barpress avoidance. In addition, the relative amount of amygdalar activation observed appeared to be related to the relative intensity of the unconditioned stimulus and somatic requirements of the task. Results suggest the CeA mediates the Pavlovian association between sensory stimuli and the BLA mediates the modulation of instrumental responding through the assignment of motivational value to the unconditioned stimulus. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Ethanol enhancement of Pavlovian conditioning.

60 New Zealand albino rabbits were tested for Pavlovian conditioning and extinction of eye-blink (EB) and heart-rate (HR) responses following water or various doses of oral ethanol (375–2,500 mg/kg). The highest dose suppressed both EB and HR conditioning during training, whereas the lowest dose enhanced HR responses during training and increased EB responses during later extinction in a symmetrically state-dependent manner. An intermediate dose (750 mg/kg) administered during training enhanced HR responses and suppressed EB responses but increased EB responses during later extinction following either ethanol or water. Ethanol treatments also suppressed unconditioned responses (UCRs) to shock and increased locomotor activity; however, these effects differed qualitatively from those that ocurred during Pavlovian training and extinction. Results suggest that very low doses of ethanol can enhance the ability of stimuli to elicit Pavlovian conditioned reflexes and impair the ability to adaptively modify these reflexes when stimulus contingencies later change. (55 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stimulus control of avoidance behavior in rats following differential or nondifferential Pavlovian training along dimensions of the conditioned stimulus.

Assigned 36 male albino Holtzman rats, following 2-way avoidance training with an auditory CS, to 1 of 6 Pavlovian manipulations: discrimination or equivalence training along frequency or intensity dimensions, nominal single stimulus training, or unsignalled shocks only. Subsequently, Ss received separate generalization tests when frequency and/or intensity were varied. Intradimensional discrimination training tended to steepen generalization gradient and resulted in a peak shift away from the negative CS (safety signal) within the frequency continuum. Pseudodiscrimination equivalence training typically reduced stimulus control, even when training and test stimuli were not along the same dimension. These modifications of avoidance generalization gradients through interpolated noncontingent training provide additional evidence of the transfer of Pavlovian control to instrumental behavior. (35 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Association learning of likes and dislikes: A review of 25 years of research on human evaluative conditioning.

Evaluative conditioning refers to changes in the liking of a stimulus that are due to the fact that the stimulus has been paired with other, positive or negative stimuli. Although evaluative conditioning appears to be subjected to certain boundary conditions, significant evaluative conditioning effects have been obtained using a large variety of stimuli and procedures. Some data suggest that evaluative conditioning can occur under conditions that do not support other forms of Pavlovian conditioning, and several models have been proposed to account for these differences. In the present article, the authors summarize the available literature, draw conclusions where possible, and provide suggestions for future research. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of dynamometer tension on stimulus generalization in schizophrenic and nonschizophrenic patients.

Replicated and extended an earlier study, to test the prediction from the W. E. Broen and L. H. Storms theory that under certain conditions schizophrenics will display an arousal-produced decrement at the training stimulus on a generalization gradient. 14 acute schizophrenics and 10 nonschizophrenics were taught to press a lever to the left when a large square was projected and to the right for a small square. These squares and 6 graded squares of intermediate size were presented during test trials, while Ss gripped a dynamometer at 0, 1/6th, and 1/3rd of maximum tension. Heart rate and skin conductance were recorded. As predicted, schizophrenics showed a significant decrement at the training stimulus under 1/3rd maximum tension but no decrement at the most remote generalization stimulus with the same dominant response. Nonschizophrenics showed no decrement at any stimuli. Heart rate but not skin conductance showed a significant increase with increased muscle tension in both groups. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The Role of Claustrum in Pavlovian Heart Rate Conditioning in the Rabbit (Oryctolagus cuniculus) : Anatomical, Electrophysiological, and Lesion Studies.

The role of the claustrum in Pavlovian heart rate (HR) conditioning was studied in the rabbit (Oryctolagus cuniculus) by (a) mapping claustral projections to the prefrontal cortex (PFC), (b) recording claustral single-unit discharge to sensory stimulation and conditioning stimuli during HR conditioning, and (c) assessing the effects of claustral damage on HR conditioning. Contralateral and ipsilateral claustral projections to the PFC were found. Claustral cells responded to nonsignal stimulation with increased discharge and also showed conditioned stimulus-evoked increases in discharge during Pavlovian HR conditioning. Moreover, claustral lesions diminished the magnitude of the HR-conditioned response without affecting the cardiac-orienting response to the conditioned stimulus or the cardiac-unconditioning response to the unconditioned stimulus, suggesting a role for the claustrum in associative learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Slow reacquisition following extinction: Context, encoding, and retrieval mechanisms.

Investigated the slow reacquisition (RAQ) of responding in rats that occurs when the conditioned stimulus/stimuli (CS) and unconditioned stimulus/stimuli (UCS) are paired again after prolonged extinction training. In Exp 1, an extinguished CS acquired less suppression than a novel CS during a final conditioning phase, but more suppression than CSs that had received comparable nonreinforcement without initial conditioning. In Exp 2, CS–UCS pairings resumed in the context of extinction caused the least RAQ of suppression: Pairings in a neutral context produced better RAQ, while return of the CS to the conditioning context caused an immediate renewal of responding to the CS. In Exp 3, a return of the CS to the extinction context after RAQ training caused renewed extinction performance and interfered with performance appropriate to RAQ. This effect was not due to demonstrable inhibitory conditioning of the extinction context. Results suggest that representations of conditioning and extinction (or CS–UCS and CS–no UCS relations) are both retained through extinction and that performance appropriate to either phase can be cued by the corresponding context. RAQ may thus be slow when the context retrieves an extinction memory. Similar mechanisms may also play a role in other Pavlovian interference paradigms. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of naloxone on conditioned suppression in rats.

Painful stimuli are known to engage an endorphin analgesic system that can be reversed by the opiate antagonist, naloxone. Naloxone, then, should increase the effectiveness of aversive unconditioned stimulus/stimuli (UCS) in Pavlovian fear conditioning. Consistent with this hypothesis, naloxone administered during the acquisition of conditioned suppression in rats enhanced posttrial suppression and preconditioned stimulus (pre-CS; context-controlled) suppression. Furthermore, it enhanced CS-elicited suppression during extinction when administered during acquisition but not when administered only during extinction. Thus naloxone does not enhance an already existing fear nor enhance the memory of previous conditioning; instead, it enhances the conditioning of fear presumably by making the aversive UCS more painful. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A model for adaptation-level effects on stimulus generalization.

Presents a quantitative model of adaptation-level (AL) effects on stimulus generalization and integrates results from single stimulus, go–no-go, and choice discrimination training paradigms. The model accurately predicts (1) the gradualness of the shift in responding during the course of asymmetrical generalization testing, (2) the relation between the degree of asymmetry and the amount of shift, (3) the effect of overrepresenting certain stimuli during testing, and (4) the effect of varying the amount of training. With the discrimination training paradigms, the effects of the degree of separation between the training stimuli and of the relative frequency of their presentation during training and subsequent generalization testing are consistent with an extension of the basic model. Finally, new research is described affirming the applicability of the AL model to several infrahuman species. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Exposure to inescapable stress persistently facilitates associative and nonassociative learning in rats.

The present study examined the proactive effects of inescapable stress on aversive Pavlovian conditioning. Stressed rats were restrained and exposed to 90 1-mA tailshocks. Twenty-four hours later, all rats were exposed to 10 conditioned stimuli (CS; 350 ms of white noise at 85 dB). Rats then received either paired training in which the CS coterminated with a 100-ms, 0.7-mA periorbital shock or the same stimuli presented in an explicitly unpaired fashion. After the unpaired exposures, these rats were also exposed to paired training. Previously stressed rats exhibited persistent sensitization to the white-noise stimulus. Stressed rats exposed to unpaired stimuli, and no longer exhibiting a sensitized response, acquired the eyeblink conditioned response at a facilitated rate when these stimuli were presented in a paired fashion. These results also demonstrate that the effect of stress on classical conditioning is long-lasting, in excess of 48 hr. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Extinction can be enhanced by a concurrent excitor.

Five experiments used rat subjects to investigate the impact on extinction of the presence of other conditioned stimuli. In Experiments 1 (Pavlovian magazine approach) and 2 (instrumental discriminative training), an excitatory stimulus (X) was extinguished alone, in conjunction with a previously reinforced other stimulus (A), in conjunction with previously nonreinforced other stimulus (B), or it was spared extinction. Responding during extinction was greatest to AX, and subsequent testing of X alone showed AX extinction to have produced the most decrement to X. Experiment 3 found similar results using a within-subject design. Experiment 5 continued separate reinforced presentations of A during extinction. This procedure not only promoted extinction of X but also converted it into a conditioned inhibitor. These experiments bear on the mechanisms of overshadowing and stimulus processing, as well as provide information on the determinants of extinction. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Modulation by the stimulus properties of excitation

Three experiments with pigeons investigated the role of excitation in a Pavlovian modulatory paradigm where the reinforcement contingencies of a conditioned stimulus (CS) were signaled by modulatory stimuli. In Experiment 1, excitatory training of the modulator that signaled reinforcement, the positive modulator, had a greater facilitative impact on discrimination learning than did excitatory training of both modulators. Although this could have resulted from simple excitatory summation, Experiment 2 revealed that excitatory training of the negative modulator also enhanced learning more than did excitatory training of both modulators. In Experiment 3, responding to CSs that had come under the control of differentially excitatory modulators was similarly controlled by new stimuli that had received simple differential excitatory training. Results suggest that excitation can play a modulatory role in Pavlovian conditioning.     

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)     

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)     

Stimulus generalization of suppression in rats following aversively motivated instrumental or Pavlovian training.

Following 100 or 300 avoidance training trials in Exp I, a total of 60 Holtzman male albino rats and their yoked Pavlovian counterparts were tested for generalization of lick suppression along the frequency dimension of the avoidance conditioned stimulus. Gradients of stimulus control were evident after 300 instrumental avoidance training trials, and additional intradimensional Pavlovian discrimination training further sharpened the gradients. After 100 trials, the yoked Pavlovian Ss suppressed more than their instrumental counterparts. However, with increased Pavlovian training, flatter gradients with decreased suppression were obtained. Results from Exp II, using 12 Ss, revealed that, whereas Pavlovian experience decreased suppression to the tone, Ss suppressed drinking in the presence of static, environmental cues. Data from both experiments support interpretations that stress the role of response control over environmental events. (20 ref) (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)     

The role of contingency in classical conditioning.

The assumption that classical conditioning depends on a contingent relation between the conditioned stimulus (CS) and the unconditioned stimulus (US), which was proposed some decades ago as an alternative to the traditional contiguity assumption, still is widely accepted as an empirical generalization, if no longer as a theoretical postulate. The first support for the contingency assumption was provided by experiments in which occasional CS–US pairings produced no response to the CS in random training—i.e., training in which the probability of the US was the same in the presence and absence of the CS. Those early experiments, the results of which too often are taken at face value, are reconsidered along with various later experiments that show conditioning, both of the CS and its context, in random training. The evidence suggests that CS–US contingency is neither necessary nor sufficient for conditioning and that the concept has long outlived any usefulness it may once have had in the analysis of conditioning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)