Evidence for "unique stimulus" account of configural conditioning.

Conducted 4 experiments with male Sprague-Dawley rats (N = 80) testing the proposition that a compound stimulus, AB, may be conceptualized as composed of the individual A and B elements as well as a separate stimulus unique to their combination. Together with an assumption about limitations on the total associative strength of the compound, this conceptualization can account for the learning of various configural conditioning paradigms. Each experiment examined whether the hypothesized unique stimulus has properties like those of a separable element. Results indicate that, like the separate elements, the unique stimulus can acquire associative strength which is either excitatory or inhibitory, which summates with other associative strengths, which influences the effectiveness of reinforcement and nonreinforcement, and which is attenuated when the unique stimulus becomes irrelevant to reinforcement. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Integrality/separability of stimulus dimensions and multidimensional generalization in pigeons.

The authors present a quantitative framework for interpreting the results of multidimensional stimulus generalization experiments in animals using concepts derived from the geometrical approach to human cognition. The authors apply the model to the analysis of stimulus generalization data obtained from pigeons trained with different sets of stimuli varying along two orthogonal dimensions. Separable pigeons were trained with stimuli varying along the dimensions of circle size and line tilt, dimensions found to be separable in previous human research; integral pigeons were trained with stimuli varying along two dimensions of rotation in depth, dimensions that are intuitively integral and which hold special interest for theories of object recognition. The model accurately described the stimulus generalization data, with best fits to the City-Block metric for separable pigeons and to the euclidean metric for integral pigeons. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

"Configural" conditioning in discrete-trial bar pressing.

Conducted 3 experiments with a total of 64 male Sprague-Dawley rats to compare responses to stimulus compounds and their elements. No loss was found when Ss responded to the elements of a repeatedly reinforced stimulus compound. When Ss were explicitly trained to discriminate between a compound and its elements, successful learning occurred regardless of whether the compound or the elements were reinforced. Addition of an explicit stimulus common to the compound and its elements retarded rather than facilitated the discrimination. Replacement of 1 element in a compound by another of similar intensity and associative strength disrupted performance. Findings rule out a number of interpretations of AB configural conditioning paradigms, but suggest that there is a unique stimulus element and limitations on the total associative strength of the compound. (16 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effects of backward pairings on the conditioning of the albino rabbit's jaw movement and nictitating membrane responses.

Evaluated backward conditioning of appetitive jaw movement and aversive nictitating membrane responses in rabbits, using 3 procedures: test trials, forward acquisition of the same response, and crossmotivational acquisition of the other response system. In both experiments, backward conditioning consisted of 3 conditioned stimulus/stimuli (CS) alone and 22 CS and unconditioned stimulus/stimuli (UCS) pairings. Contrasting the backward conditioning group with explicitly unpaired and no-treatment controls revealed that backward pairings produced no associative effects. The forward acquisition and crossmotivational acquisition tests suggest that excitatory backward acquisition of jaw movement was obtained. The forward acquisition test identified weak inhibitory conditioning of nictitating membrane responses, but the crossmotivational test implicated excitatory conditioning. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Are associative changes in acquisition and extinction negatively accelerated?

Performance to a conditioned stimulus typically shows a negatively accelerated change with Pavlovian conditioning or extinction. This is commonly attributed to negatively accelerated changes in the underlying associative learning. However, the absence of well-specified rules for mapping learning into performance makes it difficult to infer changes in the size of associative changes for stimuli occupying different points on the performance scale. This problem can be addressed by comparing responding to stimulus compounds, each consisting of 2 stimuli, 1 of which is poorly conditioned and 1 of which is well conditioned, when either the former or the latter receives a specified amount of additional training. This permits comparison at a common performance level. Two magazine-approach experiments in rats and 2 autoshaping experiments in pigeons used this technique to assess the form of the associative changes in acquisition and extinction. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

One-Trial Learning and Superior Resistance to Extinction of Autonomic Responses Conditioned to Potentially Phobic Stimuli.

Human subjects were exposed to pictures of potentially phobic (snakes) and supposedly neutral (houses) objects as conditioned stimuli (CSs) in a Pavlovian conditioning experiment with shock as unconditioned stimulus (US), and skin conductance and finger pulse volume as dependent variables. The skin conductance responses conditioned to phobic stimuli were acquired after one CS-US pairing, and showed practically no extinction, whereas the responses to neutral stimuli showed very little resistance to extinction after both 1 and 5 reinforcements. The superior resistance to extinction of the phobic condition was interpreted to be a specific associative effect. In general, the skin conductance acquisition data showed tendencies similar to those during extinction. For finger pulse volume responses, however, there were very weak conditioning effects, and no effect of stimulus. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Conditioning of stimuli with nonzero initial value.

In five experiments, rats received conditioning of either moderately attractive or moderately aversive flavors using either a strongly negative lithium chloride (LiCl) or a strongly positive Polycose as the reinforcer. In each case, testing was done with a compound of the two moderately valued stimuli to determine the amount of associative change produced by the pairing. In both within-subject and between-subjects designs, the amount of associative change was greater for a signal whose moderate value was opposite in valence from that of the reinforcer. This suggests that, like learned stimulus value, inherent stimulus value can modulate further associative learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Associative changes in elements and compounds when the other is reinforced.

Four experiments investigated the symmetry of associative changes in stimulus compounds and elements in a Pavlovian conditioned magazine-approach situation with rats. Experiment 1 used multiple groups to examine the associative changes in a conditioned element (A) as a result of its subsequent reinforcement in compound with a neutral X. These were compared with the changes in an AX compound when one of its elements (A) was subsequently reinforced alone. Although reinforcing A enhanced responding to the AX compound, compared with a control compound, reinforcing AX failed to enhance responding to A, compared with a control element. Experiments 2 and 3 made similar comparisons in a fully within-subject design, finding greater changes in a previously trained AX compound when A was subsequently conditioned than in a B element when BY was subsequently conditioned. Experiment 4 found associative decrements in A when it was reinforced in the presence of a moderately conditioned X. The results observed in each of these experiments are more consistent with an elemental model of conditioning than with a recently proposed configural model. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Classical conditioning modifies cytochrome oxidase activity in the auditory system

The effects of excitatory classical conditioning on cytochrome oxidase activity in the central auditory system were investigated using quantitative histochemistry. Rats in the conditioned group were trained with consistent pairings of a compound conditional stimulus (a tone and a light) with a mild footshock, to elicit conditioned suppression of drinking. Rats in the pseudorandom group were exposed to pseudorandom presentations of the same tone, light and shock stimuli without consistent pairings. Untrained rats in a naive group did not receive presentations of the experimental stimuli. The findings demonstrated that auditory fear conditioning modifies the metabolic neuronal responses of the auditory system, supporting the hypothesis that sensory neurons are responsive to behavioural stimulus properties acquired by learning. There was a clear distinction between thalamocortical and lower divisions of the auditory system based on the differences in metabolic activity evoked by classical conditioning, which lead to an overt learned behavioural response versus pseudorandom stimulus presentations, which lead to behavioural habituation. Increases in cytochrome oxidase activity indicated that tone processing is enhanced during associative conditioning at upper auditory structures (medial geniculate nucleus and secondary auditory cortices). In contrast, metabolic activation of lower auditory structures (cochlear nuclei and inferior colliculus) in response to the pseudorandom presentation of the experimental stimuli suggest that these areas may be activated during habituation to tone stimuli. Together these findings show that mapping the metabolic activity of cytochrome oxidase with quantitative histochemistry can be successfully used to map regional long-lasting effects of learning on brain systems.     

Rapid reacquisition in conditioning of the rabbit's nictitating membrane response.

Reacquisition after extinction often appears faster than original acquisition. However, data from conditioned suppression studies indicate that this effect may arise from spontaneous recovery and reinstatement of unextinguished contextual stimuli related to the unconditioned stimulus/stimuli (UCS). In the present experiments using the rabbit nictitating membrane preparation, spontaneous recovery was eradicated before reacquisition training. UCS contextual stimuli were controlled by retaining the UCS during extinction through explicit unpairings of the conditioned stimulus/stimuli (CS) and UCS. Attempts were also made to drive the associative strength of the CS into the inhibitory region by differential conditioning and conditioned inhibition procedures. In all cases, reacquisition was very rapid in comparison with a rest control. The results are discussed with respect to their implications for CS and UCS processing models of conditioning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Discriminated lateralized eyeblink conditioning in the rabbit: An experimental context for separating specific and general associative influences.

Four experiments demonstrated discriminated lateralized eyeblink conditioning in 38 male rabbits and showed how the phenomenon may be used to differentiate between the reflexive and emotive consequences of Pavlovian conditioning. Exps 1, 2, and 3 characterized how 2 conditioned stimuli (CSs), contemporaneously trained with left vs right paraorbital unconditioned stimuli (UCSs), can produce different CRs, each involving predominant closure of the eye ipsilateral to its UCS. Exp 4 showed how the associative tendencies controlled by additional stimuli could be evaluated by presentations in compound with such discriminanda: A 30-sec stimulus, presumed to acquire a conditioned emotional response but no eyeblink CR, equally potentiated the eyelid CRs elicited by both CSs. A 1,050-msec CS that evoked an eyeblink CR in isolation also increased the responding to both CSs but biased it toward its own lateralized CR. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Associative learning in the marsupials Didelphis albiventris and Lutreolina crassicaudata..

A procedure to study associative learning in didelphid marsupials (Didelphis albiventris and Lutreolina crassicaudata) was developed, based on the use of an appetitive unconditioned stimulus, discrete conditioned stimuli, and multiple-behavior recordings of freely moving animals. In Experiments 1 and 2, three basic conditioning phenomena were reported: differential conditioning, stimulus reversal, and summation. A specific behavior developed during the excitatory signal, independently of the particular stimulus involved, consisting of rhythmic, goal-centered, sagittal head movements, highly similar across subjects and species. Unlike previous experiments on Pavlovian conditioning in marsupials, the use of differential conditioning in within-subjects designs, with appropriate counterbalance of stimuli, precludes interpretation of these results in terms of pseudoconditioning, sensitization, or sensory-perceptual effects. These results open the possiblity for systematic research on the comparative, developmental, and neuropsychological aspects of learning to which marsupials can contribute as models. (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)     

Context specificity of conditioning, extinction, and latent inhibition.

Three experiments, using a conditioned suppression procedure with 112 male hooded Lister rats, examined the mechanisms of context specificity of conditioning, extinction, and latent inhibition. Exp I replicated previous demonstrations of context specificity of conditioning and extinction. Conditioning in one context did not necessarily transfer perfectly to another, and if extinction was carried out in a context different from that of conditioning, Ss showed a recovery of suppression when tested in the conditioning context. But both of these results disappeared when the familiarity and associative values of the 2 contexts were equated. Exp II replicated this failure to obtain context specificity of conditioning and extinction, but it did obtain context specificity of latent inhibition. Ss preexposed and conditioned to stimuli in the same context showed more profound latent inhibition than those preexposed and conditioned in different contexts. In Exp III, this effect was replicated. It is concluded that context specificity of conditioning or extinction may arise from the failure to control the associative status of the contexts used, whereas that of latent inhibition can best be explained by A. R. Wagner's (1976, 1981) theory of associative learning. Results offer no support for the view that, under conditions such as these, contexts serve as conditional cues, signaling the relationships between events occurring in their presence. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stimulus preexposure, comparison, and changes in the associability of common stimulus features

In four experiments, rats received preexposure either to both of two compound flavours (AX and BX), or to just one (BX). Experiment 1 demonstrated a perceptual learning effect, showing that, for animals given preexposure to both flavours, an aversion conditioned to AX generalized only poorly to BX. Subsequent experiments assessed the properties of the common feature, X. Experiment 3 showed that the two preexposure treatments did not differ in the extent to which they produced habituation of the neophobia evoked by X. Experiment 2 showed that conditioning to X proceeded more rapidly in subjects given preexposure to both AX and BX than in subjects preexposed to BX alone. In Experiment 4, a similar effect was found when the elements of the compounds were presented serially. It is concluded that the perceptual learning effect of Experiment 1 occurs in spite of the fact that preexposure to two stimuli tends to maintain the associability of their common elements.     

What starts an internal clock?

Five experiments with 52 male Charles River CD rats investigated under what conditions a stimulus is timed by the internal clock used in time-discrimination procedures. In Exps I–IV, Ss were trained to time one stimulus (e.g., light) and then tested as to whether they timed a stimulus from another modality (e.g., sound). The 2nd stimulus was treated in 3 ways: exposed (presented alone), paired with food, and extinguished. Exps I and II used the peak procedure, similar to a discrete-trial FI schedule, and paired the treated stimulus with food using instrumental training; Exps III and IV used a psychophysical choice procedure and paired the treated stimulus with food using classical conditioning. All 4 experiments found that there was cross-modal transfer of the time discrimination after pairing but not after exposure or extinction. This suggests that Ss' internal clock timed the treated stimulus after pairing but not after exposure or extinction. Exp V suggested that the decline of responding observed in extinction was not due to changes in timing. Thus, the internal clock apparently times stimuli with signal value (associative strength) and does not time stimuli without signal value. (46 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Simultaneous backward conditioned inhibition and mediated conditioning.

Demonstrations of retrospective revaluation suggest that remembered stimuli undergo a reduction in association with the unconditioned stimulus (US) present during learning. Conversely, demonstrations of mediated conditioning in flavor-conditioning experiments with rats suggest that remembered stimuli undergo an increase in association with the US present during learning. In a food allergy prediction task with 23 undergraduates, we demonstrated simultaneous backward conditioned inhibition and mediated conditioning effects. These results are compatible with the hypothesis that the direction of change (decrease or increase) in associative strength depends on whether the remembered stimulus was of a different category (conditioned stimulus/antecedent) or the same category (US/outcome) as the presented US. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Acquisition of automatic imitation is sensitive to sensorimotor contingency.

The associative sequence learning model proposes that the development of the mirror system depends on the same mechanisms of associative learning that mediate Pavlovian and instrumental conditioning. To test this model, two experiments used the reduction of automatic imitation through incompatible sensorimotor training to assess whether mirror system plasticity is sensitive to contingency (i.e., the extent to which activation of one representation predicts activation of another). In Experiment 1, residual automatic imitation was measured following incompatible training in which the action stimulus was a perfect predictor of the response (contingent) or not at all predictive of the response (noncontingent). A contingency effect was observed: There was less automatic imitation indicative of more learning in the contingent group. Experiment 2 replicated this contingency effect and showed that, as predicted by associative learning theory, it can be abolished by signaling trials in which the response occurs in the absence of an action stimulus. These findings support the view that mirror system development depends on associative learning and indicate that this learning is not purely Hebbian. If this is correct, associative learning theory could be used to explain, predict, and intervene in mirror system development. (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)     

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)