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Three experiments used an ABA renewal paradigm to study deepening of response loss produced by extinction of reinstated or ABC renewed fear responses. In Experiment 1, rats were trained with two stimuli, S1 and S2, in context A and extinguished to S1 in context B and S2 in context C, shocked in B but not in C, and subjected to additional extinction of S1 in B and S2 in C. Rats froze less to S1 than S2 when subsequently tested in A. In Experiments 2 and 3, following training of S1 and S2 in A, one group received extinction of S1 in B and S2 in C followed by extinction of S1 in C and S2 in B. This group froze less to S1 in A or to S2 in a novel context, D, than a group always extinguished to S1 in B and S2 in C or a group extinguished to both S1 and S2 in B and C. These results show that additional extinction of a conditioned stimulus (conditional stimulus [CS]) exhibiting either reinstatement or ABC renewal renders that CS resistant to ABA renewal. They are consistent with theories that allow a role for context in extinction learning and that use error-correction mechanisms to update this learning.

The Hall-Rodriguez (G. Hall & G. Rodriguez, 2010, Associative and nonassociative processes in latent inhibition: An elaboration of the Pearce-Hall model, in R. E. Lubow & I. Weiner, Eds., Latent inhibition: Data, theories, and applications to schizophrenia, pp. 114-136, Cambridge, England: Cambridge University Press) theory of latent inhibition predicts that it will be deepened when a preexposed target stimulus is given additional preexposures in compound with (a) a novel stimulus or (b) another preexposed stimulus, and (c) that deepening will be greater when the compound contains a novel rather than another preexposed stimulus. A series of experiments studied these predictions using a fear conditioning procedure with rats. In each experiment, rats were preexposed to 3 stimuli, 1 (A) taken from 1 modality (visual or auditory) and the remaining 2 (X and Y) taken from another modality (auditory or visual). Then A was compounded with X, and Y was compounded with a novel stimulus (B) taken from the same modality as A. A previous series of experiments (H. T. Leung, A. S. Killcross, & R. F. Westbrook, 2011, Additional exposures to a compound of two preexposed stimuli deepen latent inhibition, Journal of Experimental Psychology: Animal Behavior Processes, Vol. 37, pp. 394-406) compared A with Y, finding that A was more latently inhibited than Y, the opposite of what was predicted. The present experiments confirmed that A was more latently inhibited than Y, showed that this was due to A entering the compound more latently inhibited than Y, and finally, that a comparison of X and Y confirmed the 3 predictions made by the theory.

A series of experiments used rats to compare and contrast the effects of subjecting an already extinguished target conditioned stimulus (CS) to additional extinction in compound with either another extinguished or a nonextinguished CS. Exposure to either compound restored responding and their extinction deepened the loss of fear responses (freezing) to the target relative to a CS given equivalent extinction in isolation. This deepening was greater to the target extinguished in compound with the nonextinguished than with the extinguished CS. Summation tests showed that the target suppressed responding to an excitor or an excitatory context when it had been extinguished in compound with a nonextinguished but not with an extinguished CS. The results were interpreted to mean that additional extinction in compound with another extinguished CS resulted in the target acquiring the additional inhibition required to more fully oppose its original excitation. In contrast, additional extinction in compound with a nonextinguished CS resulted in the target acquiring not only the additional inhibition required to oppose its original excitation but also that of the nonextinguished CS, thereby converting the target into a net inhibitor., ((PsycINFO Database Record (c) 2012 APA, all rights reserved).)

The present experiments studied the role of error correction mechanisms in the latent inhibition of conditioned fear responses by conditioned stimulus (CS) preexposure. They demonstrated that a preexposed CS subjected to additional exposures in compound with either another preexposed stimulus or a novel stimulus was more latently inhibited than a preexposed CS which received additional exposures in isolation. They also showed that a preexposed CS subjected to additional exposures in compound with another preexposed stimulus was more latently inhibited than a preexposed CS given additional exposures in compound with a novel stimulus. These results were discussed in terms of the Hall-Rodriguez (2010) model of latent inhibition.

A series of experiments used the compound test procedure (Rescorla, 2002) to measure the size of spontaneous recovery of freezing responses by rats to a latently inhibited and/or extinguished conditioned stimulus (CS). The size of recovery was greater: to a pre-exposed and conditioned CS than to a CS just conditioned or just pre-exposed; to an extensively pre-exposed or extinguished CS than to a moderately pre-exposed or extinguished CS; and to a pre-exposed and extinguished CS than to a CS just pre-exposed or just extinguished. These results show that the size of recovery is proportional to the size of the depression produced by CS-alone exposures regardless of whether they occurred before, after, or both before and after conditioning. The results are discussed in terms of some contemporary models of recovery and of the inferences permitted by the use of the compound assessment technique.

We studied the learning produced by simple exposures to a stimulus. Exposures depressed orienting and subsequent conditioned freezing in rats. A remotely preexposed conditioned stimulus (CS) conditioned better and overshadowed a novel CS more than a recently preexposed CS. Additional preexposures reversed these effects: a remotely preexposed CS elicited more orienting, conditioned worse and overshadowed less than a recently preexposed CS. Exposure to a compound composed of a novel CS and a remotely preexposed CS resulted in the novel CS subsequently conditioning better than a novel CS exposed in compound with a recently preexposed CS. The results were interpreted to mean that stimulus-alone exposures produce a loss in associability which recovers across time, that this restoration deepens the loss in associability, and that this deepening is regulated by a common error term.

Previous research has reported a role for the neurotransmitter gamma-aminobutyric acid (GABA) in the extinction and renewal of conditioned fear. Here, the authors examine whether GABA is involved in the acquisition, extinction, renewal, spontaneous recovery, and latent inhibition of appetitive conditioning. Using Long-Evans rats, systemic injection of the GABA A receptor inverse agonist FG 7142 was shown to eliminate ABA renewal (Experiment 1) and spontaneous recovery (Experiment 4) of appetitive responding by selectively reducing the recovery of extinguished magazine approach. Furthermore, treatment with FG 7142 had no effects on acquisition or single-session extinction (Experiment 3) or on the context-specific expression of latent inhibition (Experiment 2). These data suggest that ABA renewal and spontaneous recovery, but not latent inhibition or responding during acquisition and an initial extinction session, are mediated by GABAergic mechanisms in appetitive Pavlovian conditioning. They provide support for the view that renewal and spontaneous recovery share a common psychological mechanism., (Copyright (c) 2009 APA, all rights reserved.)

Two groups of rats were trained for 50 days on different discriminations in a magazine approach paradigm. One group was trained with a negative patterning schedule and a positive patterning schedule concurrently: they received intermixed trials of A+, B+, AB-, C-, D-, CD+ (A, B, C, and D are four distinct stimuli; the plus sign denotes reinforcement with food, and the minus sign denotes nonreinforcement). The second group of rats was trained with the same four stimuli arranged as compounds and reinforced according to the biconditional schedule AB+, CD+, AC-, and BD-. The first group learned the positive patterning schedule much more quickly than the negative patterning schedule, but they learned the negative patterning schedule more effectively than the second group learned the biconditional schedule. The authors discuss the implications of these findings for models of stimulus representation., ((c) 2008 APA, all rights reserved.)

A series of experiments studied the amount learned about two food cues (A and B) whose presentation in a meal was followed by an allergy (+) in a fictitious patient. Participants were trained with A+ and C+ in Phase 1 and then with AB+ or AB++ in Phase 2. Subsequent testing revealed that BC was more allergenic than AD, showing that more had been learned about B than A in Phase 2. Participants were also trained with A+, then with AB+, and finally with AB++. The results of interpolating AB+ between A+ and AB++ training were consistent with the hypothesis that pretraining with Cue A selectively suppressed attention to its associate across the AB+ trials and, thereby, reduced the amount subsequently learned about B on AB++ trials., ((c) 2008 APA, all rights reserved.)

A series of experiments used a within-subject design to study spontaneous recovery of fear responses (freezing) to an extinguished conditioned stimulus (CS) in rats. Experiments 1, 2, 3, and 4 demonstrated that: a remotely extinguished CS elicited more freezing than a recently extinguished one on a common test; that the CS showing recovery underwent greater response loss across additional extinction than the one lacking recovery; and that spontaneous recovery and deepening of response loss survived reconditioning. Experiment 5 demonstrated that an excitor extinguished in compound with a CS showing recovery suffered greater loss than an excitor extinguished in compound with a CS not showing recovery, implying that the differential change is regulated by a common error term. Experiments 6 and 7 demonstrated that extinction of a compound composed of two CSs, one showing recovery and a second lacking recovery, produced greater loss to the CS that showed recovery, implying that the change is also regulated by individual error term., ((c) 2008 APA, all rights reserved.)

A series of experiments studied the effects of the interval between extinction trials on the loss of context conditioned freezing responses. Rats were shocked in one context (A) but not in another (B) and subjected to extinction trials in context A. In Experiment 1, massed trials produced more rapid loss than spaced trials. A shift from spaced to massed trials maintained this loss, but the shift from massed to spaced trials restored lost responses. Experiments 2-5 examined this effect of massed trials on responding across spaced trials. They provided evidence that (a) a single trial was as effective as multiple daily massed trials, (b) learning occurred on the first of the massed trials but not on later ones, and (c) the first trial reduced the amount learned across subsequent massed trials. Finally, alternating extinction trials in A and B produced more response loss across spaced trials than blocks of trials in A and B. The results were discussed in terms of the role accorded to self-generated priming in the models developed by A. R. Wagner (1978, 1981)., ((c) 2008 APA, all rights reserved)

When two conditioned stimuli (CSs) are presented in compound, the response is typically stronger than to the individual CSs, implying that their associative strengths combine. However, to identify exactly how associative strengths combine requires an accurate description of the relationship between associative strength and responding. The authors have used the delta rule (Rescorla & Wagner, 1972) to constrain the predicted growth of associative strength (V) to identify the relationship between V and responding across the course of Pavlovian conditioning of two CSs (one auditory, one visual). Responding to the compound was best predicted as 0.6xV(CS1)+0.6xV(CS2), suggesting that only 60% of the associative strength of each CS generalized to the compound. A second experiment confirmed this result and additionally showed that summation of responding between two same-modality CSs (both auditory or both visual) declined across training. A third experiment applied the procedure to compound conditioning, showing that responding to the compound was equal to the sum of the response rates to the individual CSs. The results are discussed in terms of configural and elemental models of Pavlovian conditioning., (Copyright (c) 2008 APA, all rights reserved.)

Exposure to a solution composed of an odor (almond) and a taste (salt) produced a context-independent preference when rats were subsequently tested with almond under a salt appetite. Postcompound exposure to either the almond or the salt alone reduced almond preferences but only when rats were tested in the extinction context. Exposure to either the almond or the salt in 1 context in advance of exposure to the compound in a different context also reduced preferences but only when the rats were tested in the context in which the element had been pre-exposed. These results show that extinction and latent inhibition of within-event learning are context specific., (Copyright (c) 2008 APA, all rights reserved.)

A series of experiments studied reacquisition of fear reactions to a completely extinguished context. Reacquisition was rapid when reconditioning occurred as soon as the fear reactions were completely extinguished, showing that the original conditioning was intact. However, when reconditioning occurred after massive extinction training, fear reactions were depressed but then recovered across a long retention interval. This recovery was due to reconditioning and was similar to that produced by conditioning a massively preexposed context. These results show that massive extinction converts a potentially dangerous context into one that is merely familiar., (((c) 2007 APA, all rights reserved).)

Rats were shocked in a context on two occasions and then tested for fear reactions as indexed by freezing. Rats spent the interval between conditioning trials and between conditioning and test in their home cages. A short interval between context-conditioning trials or between trials involving a discrete conditioned stimulus (CS) produced better learning than longer intervals. A short retention interval between conditioning and test produced better performance than longer intervals. The effects of the intertrial interval on learning are the opposite of those reported previously and are opposite to those predicted by contemporary learning theories. The effects of the training to test interval on performance are predicted by Wagner's sometimes opponent process (SOP) theory (Wagner, 1981)., (Copyright 2006 APA, all rights reserved).)

Rats were shocked in a context and then exposed to that context in the absence of shock. Shorter intervals between these extinction trials produced more long-term freezing than did longer ones, and shorter intervals between the final extinction trial and test produced more freezing than did longer ones. A short interval between a context extinction trial and test with an extinguished conditioned stimulus (CS) produced more freezing than did a longer one, and a short interval between a nonreinforced context exposure and an extinguished CS reinstated freezing when the CS was tested 24 hr later. The results suggest that recent fear acts to favor subsequent retrieval of the memory formed at conditioning rather than extinction and to render the retrieved memory more salient., (Copyright 2005 APA.)

Rats exposed to a simultaneous compound of a flavor and sucrose subsequently exhibited a preference for the flavor over water. This preference persisted across repeated testing even though the flavor was presented in the absence of sucrose. The preference did, however, extinguish if the rats were hungry when trained or tested, or if they had been reexposed to sucrose between training and test. Though failing to extinguish the preference, presentation of the flavor outside the compound protected it from the effects of sucrose devaluation, indicating that these presentations extinguished the within-compound association between the flavor and sucrose. The authors conclude that the hedonic reaction elicited by sucrose imbues the flavor with the same hedonic properties, and these properties maintain the preference independently of the flavor-sucrose association., ((c) 2004 APA, all rights reserved)

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

Five experiments studied retrograde impairments in Pavlovian fear conditioning following prolonged exposure to the opioid receptor agonist morphine. Injections of morphine commencing 1-7 days but not 14 days after conditioning produced amnesia for that conditioning episode. This amnesia was (a) selective such that morphine impaired freezing to the conditioning context but not to the auditory conditioned stimulus, (b) independent of the interval between the last injection of morphine and test, and (c) accompanied by a failure of contextual discrimination. Context preexposure protected context conditioning and discrimination from the amnestic effects of morphine. These results show that retrograde deficits in contextual fear conditioning are mediated by failures to consolidate a contextual representation.

The authors studied the role of context in reinstatement. Freezing was reinstated when the conditioned stimulus (CS) was extinguished in 1 context and rats moved to another context for reexposure to the shock unconditioned stimulus (US) and test. It was also reinstated (rather than renewed) when rats were shocked in the extinction context and moved to another context for test. This reinstatement was CS specific and reduced by nonreinforced exposures to the extinction context. Rats shocked in the context in which a stimulus had been preexposed froze when tested in another context. These findings suggest 2 roles for context in reinstatement: conditioning of the test context (M. E. Bouton, 1993) and mediated conditioning by the extinction context (P. C. Holland, 1990).

We used 1-, 2-, and 3-context designs to study the control exerted by contexts over freezing in rats exposed to a conditioned stimulus (CS) in advance of its pairing with a shock unconditioned stimulus. The latent inhibition observed when preexposure, conditioning, and testing occurred in the same context was attenuated if preexposure occurred in a different context to conditioning and testing. Latent inhibition (i.e., attenuated performance) was restored in a CS-specific manner if preexposure and testing occurred in the same context and conditioning in a different one. Latent inhibition was also reduced by a long retention interval but remained specific for a particular context-CS relation. Finally, CS preexposure resulted in contextual control over the expression of excitatory conditioned performance. The results are discussed in terms of memory, associative, and associative-performance models of CS-preexposure effects.

Four experiments studied contextual control over rats' freezing to conditioned stimuli (CSs) that had been paired with shock and were then extinguished. In Experiment 1, rats were exposed to a CS A-shock and a CS B-shock pairing in Context C. CS A was then extinguished in Context A, and CS B in Context B. Freezing was renewed when each CS was presented in the context where the other CS had been extinguished. In Experiments 2-4, rats were exposed to a CS A-shock pairing in A and a CS B-shock pairing in B. They were then exposed to Context C where one, both, or neither of the CSs were extinguished, or where both CSs continued to be reinforced. On test, the rats froze more to CS A than to CS B in Context A, and more to CS B than to CS A in Context B, but only if the CSs had been extinguished. Thus, after extinction, rats use contexts to regulate retrieval not only of their memory for extinction, but also of their memory for the original conditioning episode.

Rats acquired a preference for an aqueous odor (almond) presented in simultaneous compound with sucrose. Separate presentations of saccharin reduced this preference in rats with ad-lib access to food during training or at test, but not in rats that were hungry during both training and test. In contrast, separate presentations of sucrose reduced the preference for the almond irrespective of deprivation state during training and test. We interpret the results to mean that a hungry rat forms odor-taste and odor-calorie associations, and its motivational state on test determines which of these associations controls the preference. In contrast, a rat that is not hungry during training only forms an odor-taste association, and its performance on test is independent of its level of hunger.

Rats were injected with a benzodiazepine (midazolam) and shocked after presentation of an auditory conditioned stimulus (CS). They were then tested for fear reactions (freezing) to the CS in either the original context or a 2nd context after either a short (1-day) or long (21-day) retention interval. Rats tested in the original context froze less after 1 day than rats tested after that interval in the 2nd context or rats tested after 21 days. Moreover, rats tested after the long interval in the original context froze less than rats tested after that interval in the 2nd context. Therefore, midazolam does not impair the acquisition of conditioned fear but regulates when and where that fear is expressed. These effects of midazolam were interpreted as a contextually controlled deficit in the expression of conditioned fear that is similar to that associated with latent inhibition and extinction (M. E. Bouton, 1993).

Three experiments exposed rats (Rattus norvegicus) to a discriminative conditioning procedure whereby a specific fluid was followed by lithium in one environment but not in another. This produced context-specific aversion to water, as detected by 2-bottle tests in Experiment 1, and a context-dependent saccharin aversion, which was unaffected by context extinction, in Experiment 2. Experiment 3 found that sucrose preexposure increased contextual control over the aversion established by sucrose-lithium pairings but had no effect on the target context. By contrast, target context exposure during conditioning reduced aversion to this context but did not affect contextual control of the sucrose aversion. In conclusion, depending on the conditioning procedures, contextual control of a taste aversion can be independent of the context's Pavlovian properties.

Hypoalgesia and fear co-occurred in rats trained on a heated floor and tested for their latencies to paw lick on that floor and to step down onto a nonheated floor. These responses were extinguished, suggesting a mediation by aversive conditioning processes. A benzodiazepine impaired the acquisition of aversive conditioning, but it did not attenuate the expression of conditioned hypoalgesia. The opioid agonist morphine also impaired acquisition across a range of drug doses and variations in hypoalgesic tolerance, whereas the opioid antagonist naloxone facilitated acquisition. The results are discussed in terms of the perceptual-defensive-recuperative (Fanselow, 1986) and working memory (Grau, 1987) models of the mechanisms for the co-occurrence of conditioned hypoalgesia and fear.

Six experiments employed an odor-aversion paradigm to investigate the role of the duration of exposure to an odor in determining that odor's subsequent associability with illness. Rats were exposed to an odor at times T1 and T2, and the second of these exposures was followed by toxicosis. When the initial odor exposure was brief, the odor aversion was attenuated with a moderate T1-T2 interval of 3 hr (Experiment 1) but not with long intervals of 28 hr and 76 hr (Experiment 2). In contrast, when the initial odor exposure was long, the odor aversion was attenuated at a long T1-T2 interval (Experiment 3). With a T1-T2 interval of 24 hr, a brief initial exposure did not attenuate odor aversions when the context either remained the same or was changed from T1 to T2, whereas a long initial exposure attenuated such aversions when the context remained the same but not when the context was changed (Experiment 4). With a T1-T2 interval of 3 hr, a brief initial exposure attenuated odor aversions when the context remained the same or was changed from T1 to T2, whereas a long initial exposure attenuated such aversions when the context remained the same but not when the context was changed (Experiment 5). A brief exposure at T1, either with or without a subsequent context "extinction," attenuated odor aversions when the T1-T2 interval was 3 hr but not when this interval was 24 hr; a long initial exposure at T1, without a subsequent context "extinction," attenuated odor aversions when the T1-T2 interval was 4 hr and 24 hr but with a subsequent context "extinction" did not attenuate such aversions at either 4-hr or 24-hr T1-T2 intervals (Experiment 6). The results demonstrate that the duration of exposure to an odor determined whether that odor presentation caused short- or long-term decrements in odor conditionability and are discussed in terms of the relation between self- and retrieval-generated processes.