Training history affects magnitude of spontaneous recovery from extinction of appetitive conditioned responding

Three experiments examined spontaneous recovery from extinction of appetitive conditioned responding (CR) as a function of training history. Rats first received reinforced and non-reinforced conditioning trials. Groups of rats were equated for total number of reinforced trials but differed in the number of non-reinforced trials, or in the order of reinforced and non-reinforced trials. CR was then extinguished in all groups. Subsequently, the extent of recovery of CR was assessed in a test session performed either 1 or 17 days after the last extinction session. After a 17-day delay, rats that had received all reinforced trials immediately prior to the first extinction session showed stronger recovery than did rats having received all reinforced trials at the beginning of training, or interspersed among non-reinforced trials. No significant spontaneous recovery was observed after a 1-day test delay. These results, which may be of clinical relevance with respect to relapse after therapy, are explained in terms of the training schedules generating differences in strength of inhibitory associations, and a relatively long, but not a short, test delay attenuating these associations.     

Effects of training history on resurgence in humans

This experiment assessed the effects of training history on resurgence in three college students. Four-choice arbitrary-matching-to-sample trials occurred in two components of a multiple schedule. An A1 or A2 sample stimulus and four (B) comparison stimuli occurred on AB trials, and a C1 or C2 sample stimulus and four (D) comparison stimuli occurred on CD trials. By the end of training, accuracy and latency measures were comparable across separate discriminations, selecting B2 in the presence of A2 and selecting D2 in the presence of C2, despite a lengthier training correlated with the former discrimination. Next, in the presence of A2 and C2, respectively, responses to B2 and D2 were extinguished and responses to B3 and D3 were reinforced. These responses to B3 and D3 then were extinguished in a final condition. In this final condition, resurgence to B2 occurred for each participant, whereas resurgence to D2 occurred for only one participant. Thus, there was greater resurgence of the discrimination with the lengthier training history, despite the discriminations being similar in terms of accuracy and latency before extinction. This result, therefore, can be classified as a latent, or remote, behavioral history effect.     

Pavlovian conditional stimuli cannot always be defined solely in physical terms

Twenty-four university students received differential Pavlovian conditioning with two colored stimuli separately accompanied by shock, and two other colored stimuli separately presented without shock. The reinforced and nonreinforced pairs of stimuli both contained complementary elements. After differentiation between the reinforced and nonreinforced elements was established, the complementary pairs were each additively mixed, (i.e., presented at the same time and in the same locus), producing two identical white compounds (established by pilot study). The subjects' skin-conductance responses to the two compounds showed that their different conditioning histories did not result in different responses. Rather, a simple declining function was obtained, resembling habituation or extinction. It was concluded that the definition of the conditional stimulus as a physical event is inappropriate in studies in which physically different stimuli may result in identical internal processes (or phenomenologic experiences)--for example, in additive color mixture.     

Generalization of EMG biofeedback training

Five young adults received audio biofeedback training to reduce trapezius EMG levels while they engaged in reading in an office, seated at a table. A multiple-baseline-across subjects design was employed in two separate studies. After training, all subjects demonstrated reduced EMG levels while reading in a home or library setting. The first study suggested that subjects reduced EMG levels by minimizing movements and altering their postures; the second study systematically demonstrated changes in such behavior, which was correlated with EMG levels. The data provide evidence that EMG biofeedback resulted in response generalization across several motoric classes, and in stimulus generalization from the training setting to the natural environment. The importance of assessing generalization is discussed.     

Generalization of EMG biofeedback training

Five young adults received audio biofeedback training to reduce trapezius EMG levels while they engaged in reading in an office, seated at a table. A multiple-baseline-across subjects design was employed in two separate studies. After training, all subjects demonstrated reduced EMG levels while reading in a home or library setting. The first study suggested that subjects reduced EMG levels by minimizing movements and altering their postures; the second study systematically demonstrated changes in such behavior, which was correlated with EMG levels. The data provide evidence that EMG biofeedback resulted in response generalization across several motoric classes, and in stimulus generalization from the training setting to the natural environment. The importance of assessing generalization is discussed.     

Differential resurgence and response elimination

Resurgence refers to the transient recovery of previously reinforced, but presently not reinforced, responding when more recently reinforced responding is extinguished. The primary purpose of our research was to determine how differential resurgence results from the procedures used to eliminate that responding. There were three conditions in each of five experiments. In Condition 1, key pecking by pigeons was maintained under a two-component multiple variable-interval (VI) 30-s VI 30-s schedule. In Condition 2, this pecking was eliminated in different ways across components. In Condition 3, extinction was in effect for all responses, and resurgence of key pecking was compared across components. These three conditions were repeated for most pigeons, and the procedures used to eliminate responding in Condition 2 varied across experiments. In Experiment 1, there was greater resurgence, and an earlier onset of it, after a differential-reinforcement-of-other-behavior (DRO) schedule than after a VI schedule was correlated with pecking an alternative key. Experiments 2 and 3 showed that the differential resurgence in Experiment 1 probably was not due to conditional stimulus control or the periodicity of food delivery, respectively. In Experiment 4, there was no systematic difference in resurgence after either a DRO schedule or a VI schedule correlated with treadle pressing. In Experiment 5, there was greater resurgence, and/or an earlier onset of it, after a VI schedule correlated with treadle pressing than after a VI schedule correlated with pecking an alternative key. Taken together, the results showed that the reinforcement of an alternative key-peck response was the most effective means of reducing subsequent key-peck resurgence. The relation of these results to an understanding of resurgence is discussed.     

Extinction, relapse, and behavioral momentum

Previous experiments on behavioral momentum have shown that relative resistance to extinction of operant behavior in the presence of a discriminative stimulus depends upon the baseline rate or magnitude of reinforcement associated with that stimulus (i.e., the Pavlovian stimulus-reinforcer relation). Recently, we have shown that relapse of operant behavior in reinstatement, resurgence, and context renewal preparations also is a function of baseline stimulus-reinforcer relations. In this paper we present new data examining the role of baseline stimulus-reinforcer relations on resistance to extinction and relapse using a variety of baseline training conditions and relapse operations. Furthermore, we evaluate the adequacy of a behavioral momentum based model in accounting for the results. The model suggests that relapse occurs as a result of a decrease in the disruptive impact of extinction precipitated by a change in circumstances associated with extinction, and that the degree of relapse is a function of the pre-extinction baseline Pavlovian stimulus-reinforcer relation. Across experiments, relative resistance to extinction and relapse were greater in the presence of stimuli associated with more favorable conditions of reinforcement and were positively related to one another. In addition, the model did a good job in accounting for these effects. Thus, behavioral momentum theory may provide a useful quantitative approach for characterizing how differential reinforcement conditions contribute to relapse of operant behavior.     

Relative temporal representations in Pavlovian conditioning

The transfer of relative temporal representations was assessed in a series of three experiments. In each experiment, rats (Rattus norvegicus) received one set of conditioned stimulus (CS) and intertrial interval (ITI) durations in Phase 1 and another set in Phase 2. The ratio between the CS and ITI intervals was either changed or maintained across phases. On the hypothesis that relative temporal representations are learned, groups receiving maintained temporal ratios across phases were expected to display greater change in responding upon encountering the new intervals. When the CS duration decreased across phases, maintaining the temporal ratio did lead to greater change in Day 1 of Phase 2 towards the final pattern of responding. However, when the CS increased across phases, maintaining the temporal ratio across phases did not facilitate adjustment to the new intervals, suggesting that extinction of previously reinforced times induced new learning. These results provide evidence that under some conditions, relative relationships in temporal maps may survive transformation-of-scale, like relative relationships in spatial maps.     

Effects of an extinguished CS on competition with another CS

Three experiments were conducted using a conditioned taste aversion procedure with rats to examine the effect of nonreinforced presentations of a conditioned stimulus (CS) on its ability to compete with a target stimulus for manifest conditioned responding. Two CSs (A and B) were presented in a serial compound and then paired with the unconditioned stimulus. CS A was first paired with the US and then presented without the US (i.e., extinction) prior to reinforced presentation of the AB compound. Experiment 1 showed that A was poor at competing with B for conditioned responding when given conditioning and extinction prior to reinforcement of AB relative to a group that received both A and B for the first time during compound conditioning. That is, an extinguished A stimulus allowed greater manifest acquisition to B. Experiment 2 found that extinction treatment produced a poor CR to the pretrained and extinguished CS itself following compound conditioning. Experiment 3 found that interposing a retention interval after extinction of A and prior to compound conditioning enhanced A's ability to compete with B. The results of these experiments are discussed with regard to different theories of extinction and associative competition.     

Effects of conditioning history on selective stimulus control by elements of compound discriminative stimuli

Effects of prior discrimination training on stimulus control by color and shape dimensions of compound stimuli were studied with college students. In Phase 1, single-stimulus discrimination training was conducted for two values of color and shape. Phase 2 discrimination training employed two 2-dimensional compound stimuli composed of the color and shape stimuli trained in Phase 1. For conflict-compound stimuli, the stimulus-response-consequence contingency was altered between phases for one stimulus dimension (target dimension), but not for the other, non-target, dimension. Level of congruence (100%, 25%, and 0%) of the contingency for the target dimension between phases was manipulated across groups. When each stimulus value was tested in Phase 3, level of Phase-2-consistent responding to the target dimension varied with level of Phase-1-to-Phase-2 congruence. In Experiment 2, training history for the non-target dimension was altered across three conditions: (a) Correlated with reinforcement, as in Experiment 1, (b) No-Training, or (c) Not-Correlated. Phase-2-consistent responding to the target cue in Phase 3 was lower under the latter conditions than under the Correlated condition, indicating that the non-target dimension modulated control by the target dimension, consistent with stimulus competition. The data suggest elemental, rather than configural processing of the compound stimuli during Phase 2.     

Intertrial interval as a contextual stimulus

Four experiments with rats investigated whether the time between appetitive conditioning trials can serve as a discriminative cue for responding during the next conditional stimulus (CS). In Experiment 1, rats that received extinction trials with a 4-min intertrial interval (ITI) showed spontaneous recovery after a retention interval of 16 min, whereas rats that received extinction with a 16-min ITI did not. Experiments 2 and 3 investigated more explicit discriminations between the 4- and 16-min ITIs. When a 16-min ITI signaled that the CS would be reinforced and a 4-min ITI signaled that it would not, the ITIs modulated responding to the CS. But when the 4-min ITI signaled reinforcement and the 16-min ITI did not, there was less evidence of modulation by the ITIs. This asymmetry was due at least partly to a difficulty in performance rather than learning. Experiment 4 investigated similar discriminations with 1- and 4-min ITIs. Here the results took a different form: time in the reinforced ITI elicited responding directly, but did not modulate responding to the CS. ITI can function as a contextual cue, and the results suggest new similarities between the processes behind interval timing and associative learning.     

The role of contextual conditioning in the effect of reinforcer devaluation on instrumental performance by rats

Different groups of rats received different amounts of training to lever press for a food reinforcer before an aversion was conditioned to the food. This devaluation of the reinforcer reduced responding in both subsequent extinction and reinforced tests of responding to a degree that was independent of the amount of instrumental training. Moreover, interpolating context extinction between aversion conditioning and the extinction test reduced the magnitude of the devaluation effect, thereby indicating that Pavlovian contextual conditioning may play a role in the instrumental devaluation effect.     

Associative symmetry and stimulus-class formation by pigeons: The role of non-reinforced baseline relations

Two experiments tested the assumption of Urcuioli's (2008) theory of pigeons’ equivalence-class formation that consistent non-reinforcement of certain stimulus combinations in successive matching juxtaposed with consistent reinforcement of other combinations generates stimulus classes containing the elements of the reinforced combinations. In Experiment 1, pigeons were concurrently trained on symbolic (AB) and two identity (AA and BB) successive tasks in which half of all identity trials ended in non-reinforcement but all AB trials were reinforced, contingent upon either responding or not responding to the comparisons. Subsequent symmetry (BA) probe trials showed evidence of symmetry in one of four pigeons. In Experiment 2, pigeons learned three pair-comparison tasks in which left versus right spatial choices were reinforced after the various sample-comparison combinations comprising AB, AA, and BB conditional discriminations. Non-differentially reinforced BA probe trials following acquisition showed some indication of symmetrical choice responding. The overall results contradict the theoretical predictions derived from Urcuioli (2008) and those from Experiment 2 challenge other stimulus-class analyses as well.     

Worrying affects associative fear learning: a startle fear conditioning study

A valuable experimental model for the pathogenesis of anxiety disorders is that they originate from a learned association between an intrinsically non-aversive event (Conditioned Stimulus, CS) and an anticipated disaster (Unconditioned Stimulus, UCS). Most anxiety disorders, however, do not evolve from a traumatic experience. Insights from neuroscience show that memory can be modified post-learning, which may elucidate how pathological fear can develop after relatively mild aversive events. Worrying--a process frequently observed in anxiety disorders--is a potential candidate to strengthen the formation of fear memory after learning. Here we tested in a discriminative fear conditioning procedure whether worry strengthens associative fear memory. Participants were randomly assigned to either a Worry (n = 23) or Control condition (n = 25). After fear acquisition, the participants in the Worry condition processed six worrisome questions regarding the personal aversive consequences of an electric stimulus (UCS), whereas the Control condition received difficult but neutral questions. Subsequently, extinction, reinstatement and re-extinction of fear were tested. Conditioned responding was measured by fear-potentiated startle (FPS), skin conductance (SCR) and UCS expectancy ratings. Our main results demonstrate that worrying resulted in increased fear responses (FPS) to both the feared stimulus (CS(+)) and the originally safe stimulus (CS(-)), whereas FPS remained unchanged in the Control condition. In addition, worrying impaired both extinction and re-extinction learning of UCS expectancy. The implication of our findings is that they show how worry may contribute to the development of anxiety disorders by affecting associative fear learning.     

Extinction as discrimination: the molar view

The traditional molecular view of behavior explains extinction as the dissipation or inhibition of strength, formerly built up by contiguous reinforcement. In obstinate opposition to this explanation was the partial-reinforcement extinction effect: a partially reinforced response extinguishes more slowly than a continuously reinforced response. It suggests instead that extinction is discrimination. Four pigeons were exposed to daily sessions in which a variable period of food delivery, produced by pecking on a variable-interval schedule, was followed by extinction. The rate of food delivery was varied over a wide range across conditions. Varying the amount of food per delivery inversely with rate of delivery kept response rate from varying excessively. The results confirmed and extended the partial-reinforcement effect; persistence of pecking and time to extinction were inversely related to rate of obtaining food. The results support the molar view of extinction, not as loss of strength of a particular discrete response, but as a transition from one allocation of time among activities to another. Although molecular theories dismiss discrimination due to repeated training and extinction as an impurity or complication, repeated cycles of availability and privation are probably typical of the environment in which most vertebrate species evolved.     

Fear Conditioning Induced by Interpersonal Conflicts in Healthy Individuals

Psychophysiological markers have been focused to investigate the psychopathology of psychiatric disorders and personality subtypes. In order to understand neurobiological mechanisms underlying these conditions, fear-conditioning model has been widely used. However, simple aversive stimuli are too simplistic to understand mechanisms because most patients with psychiatric disorders are affected by social stressors. The objective of this study was to test the feasibility of a newly-designed conditioning experiment using a stimulus to cause interpersonal conflicts and examine associations between personality traits and response to that stimulus. Twenty-nine healthy individuals underwent the fear conditioning and extinction experiments in response to three types of stimuli: a simple aversive sound, disgusting pictures, and pictures of an actors’ face with unpleasant verbal messages that were designed to cause interpersonal conflicts. Conditioned response was quantified by the skin conductance response (SCR). Correlations between the SCR changes, and personality traits measured by the Zanarini Rating Scale for Borderline Personality Disorder (ZAN-BPD) and Revised NEO Personality Inventory were explored. The interpersonal conflict stimulus resulted in successful conditioning, which was subsequently extinguished, in a similar manner as the other two stimuli. Moreover, a greater degree of conditioned response to the interpersonal conflict stimulus correlated with a higher ZAN-BPD total score. Fear conditioning and extinction can be successfully achieved, using interpersonal conflicts as a stimulus. Given that conditioned fear caused by the interpersonal conflicts is likely associated with borderline personality traits, this paradigm could contribute to further understanding of underlying mechanisms of interpersonal fear implicated in borderline personality disorder.     

Hippocampal State-Dependent Behavioral Reflex to an Identical Sensory Input in Rats

We examined the local field potential of the hippocampus to monitor brain states during a conditional discrimination task, in order to elucidate the relationship between ongoing brain states and a conditioned motor reflex. Five 10-week-old Wistar/ST male rats underwent a serial feature positive conditional discrimination task in eyeblink conditioning using a preceding light stimulus as a conditional cue for reinforced trials. In this task, a 2-s light stimulus signaled that the following 350-ms tone (conditioned stimulus) was reinforced with a co-terminating 100-ms periorbital electrical shock. The interval between the end of conditional cue and the onset of the conditioned stimulus was 4±1 s. The conditioned stimulus was not reinforced when the light was not presented. Animals successfully utilized the light stimulus as a conditional cue to drive differential responses to the identical conditioned stimulus. We found that presentation of the conditional cue elicited hippocampal theta oscillations, which persisted during the interval of conditional cue and the conditioned stimulus. Moreover, expression of the conditioned response to the tone (conditioned stimulus) was correlated with the appearance of theta oscillations immediately before the conditioned stimulus. These data support hippocampal involvement in the network underlying a conditional discrimination task in eyeblink conditioning. They also suggest that the preceding hippocampal activity can determine information processing of the tone stimulus in the cerebellum and its associated circuits.     

Genetic Control of Startle Behavior in Medaka Fish

Genetic polymorphisms are thought to generate intraspecific behavioral diversities, both within and among populations. The mechanisms underlying genetic control of behavioral properties, however, remain unclear in wild-type vertebrates, including humans. To explore this issue, we used diverse inbred strains of medaka fish (Oryzias latipes) established from the same and different local populations. Medaka exhibit a startle response to a visual stimulus (extinction of illumination) by rapidly bending their bodies (C-start) 20-ms after the stimulus presentation. We measured the rates of the response to repeated stimuli (1-s interval, 40 times) among four inbred strains, HNI-I, HNI-II, HO5, and Hd-rR-II1, and quantified two properties of the startle response: sensitivity (response rate to the first stimulus) and attenuation of the response probability with repeated stimulus presentation. Among the four strains, the greatest differences in these properties were detected between HNI-II and Hd-rR-II1. HNI-II exhibited high sensitivity (approximately 80%) and no attenuation, while Hd-rR-II1 exhibited low sensitivity (approximately 50%) and almost complete attenuation after only five stimulus presentations. Our findings suggested behavioral diversity of the startle response within a local population as well as among different populations. Linkage analysis with F2 progeny between HNI-II and Hd-rR-II1 detected quantitative trait loci (QTL) highly related to attenuation, but not to sensitivity, with a maximum logarithm of odds score of 11.82 on linkage group 16. The three genotypes (homozygous for HNI-II and Hd-rR-II1 alleles, and heterozygous) at the marker nearest the QTL correlated with attenuation. Our findings are the first to suggest that a single genomic region might be sufficient to generate individual differences in startle behavior between wild-type strains. Further identification of genetic polymorphisms that define the behavioral trait will contribute to our understanding of the neural mechanisms underlying behavioral diversity, allowing us to investigate the adaptive significance of intraspecific behavioral polymorphisms of the startle response.     

Prototype symbolization in hooded crows

The ability in prototype symbolization was studied in four crows trained in matching concept. The experimental approach was characterized by the absence of direct training providing an association between the pictured arrays and Arabic numerals. Experimental sessions were divided into demonstrative and test phases. In the demonstrative phases, the sample and the reinforced stimulus belonged to the same category: if the sample was a pictured array, the reinforced stimulus was also the pictured array, if the sample was a numeral, the reinforced stimulus was likewise a numeral. Matching-to-sample competence was sufficient to perform this task successfully. In case of a correct choice a crow received some mealworms, their number was equal to the number of items in the pictured array or the Arabic numeral. In the test phases, the sample and the comparison stimuli were of different categories. If the sample was a pictured array, the comparison stimuli were numerals; if the sample was a numeral, the comparisons were the pictured arrays. Such tests required the birds to choose a numeric symbol corresponding to the pictured array or to choose the array of pictured items numerically equal to the Arabic symbol. All four crows performed this task successfully. Birds were able to set up a correspondence between the Arabic numeral from 1 to 4 and the number of elements in pictured arrays by way of mental juxtaposition of the earlier received information. Similar experiments showed that crows are likely to be able to perform mental operations with numerals analogous to simple arithmetic addition.     

Stimulus specificity in the acquisition and extinction of conditioned taste aversion

An experiment evaluated whether the acquisition and extinction of conditioned taste aversion in the rat is stimulus-specific by testing the degree of response transfer between sweet and salty tastes. Animals in the paired-same and paired-different groups received a presentation of a gustatory CS and a cyclophosphamide injection US. Nonconditioned control groups received unpaired CS /US presentations or the CS followed by a vehicle injection. Taste avoidance was evaluated in three nonreinforced test sessions. In the paired-same, unpaired and vehicle groups, all test sessions were conducted with the same flavor as originally used in training, whereas the paired-different group was tested with a novel flavor on the first and second sessions and with the originally trained flavor in last session. Stimulus specific acquisition was apparent in the first test session, when the animals in the group paired-same exhibited lower fluid intake than the other three groups. Evidence of specificity of extinction was apparent in the last test session, when animals in the group paired-different exhibited lower fluid intake than the other three groups. These results provide further evidence of stimulus specificity in acquisition and extinction of conditioned taste aversion, supporting the associative interpretation of these phenomena.