Differential control by context in the inflation and reinstatement paradigms.

Examined, in 5 conditioned suppression experiments, the influence of summation between fear of the CS and the context in experimental paradigms in which the rat is exposed to UCSs following conditioning or extinction. Context-preference tests assessed contextual fear. In Exps I–III with 88 female Wistar rats, the inflation paradigm, in which fear of a CS paired with a weak UCS is enhanced by exposure to intense UCS alone, was investigated. Results show that the contextual fear that was present when the target CS was tested was reduced by presenting the intense UCSs in a different context, by exposing Ss to the context following their presentation, and by signaling the intense UCSs with a 2nd CS. In Exp IV with 32 female Wistar rats, UCS exposures following conditioning or extinction both produced contextual fear, but only fear of the extinguished CS was reinstated by that fear. In Exp V with 32 female Wistar rats, identical amounts of contextual fear reinstated fear of an extinguished CS, but not a nonextinguished CS, when the 2 types of CSs were arranged to evoke comparable amounts of fear prior to testing. It is suggested that contextual fear plays a role in the reinstatement paradigm but not in the inflation paradigm. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Contextual control of the extinction of conditioned fear: Tests for the associative value of the context.

When male Wistar rats received pairings of a CS with shock in one context and then extinction of the CS in another, fear of the CS was renewed when the CS was returned to and tested in the original context (Exps I and III; 40 Ss). No such renewal was obtained when the CS was tested in a 2nd context after extinction had occurred in the conditioning context (Exp IV; 24 Ss). In Exp II, shocks presented following extinction reinstated fear of the CS, but only if they were presented in the context in which the CS was tested. In each experiment, the associative properties of the contexts were independently assessed. Contextual excitation was assessed primarily with context-preference tests in which Ss chose to sit in either the target context or an adjoining side compartment. Contextual inhibition was assessed with summation tests. Although reinstatement was correlated with demonstrable contextual excitation present during testing, the renewal effect was not. There was no evidence that contextual inhibition developed during extinction. Results suggest that fear of an extinguished CS can be affected by the excitatory strength of the context but that independently demonstrable contextual excitation or inhibition is not necessary for contexts to control that fear. (41 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Recent Exposure to a Dangerous Context Impairs Extinction and Reinstates Lost Fear Reactions.

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. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Deepened extinction from compound stimulus presentation.

Three experiments with rats and 2 with pigeons explored the effect of presenting 2 extinguished excitatory stimuli in compound. Four learning situations were used: Pavlovian magazine approach, Pavlovian fear conditioning, and instrumental discriminative instrumental learning in rats, as well as Pavlovian sign tracking in pigeons. All 5 experiments confirmed D. Reberg's (1972) observation that even after extinction of the individual stimuli, presenting them in compound evoked substantial responding. Moreover, nonreinforcement of that compound deepened extinction of an element more substantially than did additional presentation of that element alone. Such compound exposure reduced spontaneous recovery, reduced reinstatement, and slowed subsequent reconditioning. The primary determinant seemed to be the enhanced associative strength rather than the enhanced conditioned responding that occurred during the nonreinforced compound. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of context on performance to conditioned stimuli with mixed histories of reinforcement and nonreinforcement.

Five conditioned suppression experiments, with 160 Wistar rats, explored the role of the conditioning history of the conditioned stimulus (CS) in determining the effects of contextual fear on performance to the CS. Contextual fear was produced by postconditioning exposure to unconditioned stimulus/stimuli (UCS) alone in the context of conditioning; it was independently assessed with context-preference tests. When the number of reinforced and nonreinforced trials was equated across extinction, partial reinforcement, and latent inhibition procedures, only the extinction procedure produced a CS whose performance was subsequently affected (i.e., augmented) by contextual fear. Contextual fear's relatively unique augmenting effect on fear of an extinguished CS was abolished by extensive, but not by less extensive, reacquisition training. Results indicate that, depending on the CS's conditioning history, contextual fear either augments or has little effect on fear of the CS. It is suggested that augmentation by context should be viewed as the restoration of fear that is otherwise depressed by extinction. (28 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effects of neurotoxic hippocampal lesions on two effects of context after fear extinction.

Three conditioned suppression experiments with rats examined the role of the hippocampus in 2 effects of context after extinction. Reinstatement is the context-specific recovery of fear to an extinguished conditioned stimulus (CS) that occurs following independent presentations of the unconditioned stimulus (UCS), after extinction. Renewal is the recovery of fear when the CS is presented in the context in which it was conditioned, after extinction in a different context. Results indicated that neurotoxic lesions of the hippocampus, performed before conditioning, abolished reinstatement, which depends on context–UCS associations, but not renewal, which does not. This dissociation is not the result of differences in the recentness of context learning that ordinarily governs the 2 effects. The results suggest that the hippocampus is necessary for some, but not all, types of contextual learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

D-cycloserine facilitates extinction but does not eliminate renewal of the conditioned emotional response.

The effect of D-cycloserine (DCS), an NMDA partial agonist, on extinction of fear was investigated in rats using the conditioned emotional response preparation. Fear extinction was facilitated when the first 4 trials occurred with a 30-mg/kg dose of DCS. However, extinguished fear was "renewed" regardless of the drug treatment when the rats were returned to the context in which fear had been conditioned. Additional results suggest that DCS's facilitation of extinction is a small but meaningful effect in the current method. The results suggest caution regarding the use of DCS as an adjunct to extinction: Although the drug may modestly facilitate extinction learning, it does not necessarily destroy the potential for relapse. Behavioral mechanisms are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A developmental dissociation of context and GABA effects on extinguished fear in rats.

Although extinction has attracted considerable attention in recent years, there has been very little empirical work on extinction during development. Using Pavlovian fear conditioning, the authors provide evidence for developmental differences in extinction. Specifically, Postnatal Day (PND) 23 rats exhibited recovery of an extinguished freezing response to an auditory conditioned stimulus when tested in a context different from that in which extinction occurred (i.e., renewal) or when injected with the gamma-amino butyric acid (GABA) inverse agonist FG7142 prior to test. In contrast, PND 16 rats failed to exhibit either of these effects, although a subsequent experiment demonstrated that FG7142 alleviated spontaneous forgetting in PND 16 rats. Taken together, it appears that there are fundamental differences in the processes involved in extinction across development. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effect of yohimbine on the extinction of conditioned fear: A role for context.

Six experiments with rat subjects examined the effect of yohimbine, an alpha-2 adrenergic autoreceptor antagonist, on the extinction of conditioned fear to a tone. Experiments 1 and 2 demonstrated that systemic administration of yohimbine (1.0 mg/kg) facilitated a long-term decrease in freezing after extinction, and this depended on pairing drug administration with extinction training. However, Experiments 3 and 4 demonstrated that yohimbine did not eradicate the original fear learning: Freezing was renewed when the tone was tested outside of the extinction context. Experiments 5 and 6 found that the contextually specific attenuation of fear produced by yohimbine transferred to another extinguished conditional stimulus (CS) and not to a nonextinguished CS. The results suggest that yohimbine, when administered in the presence of a neutral context, creates a form of inhibition in that context that allows that specific context to reduce fear of an extinguished CS. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

State-dependent fear extinction with two benzodiazepine tranquilizers.

Investigated whether fear extinction conducted under the influence of a benzodiazepine transfers to the undrugged state in rats. Fear was conditioned by pairing an experimental chamber with footshock and was assessed by observing freezing, a characteristic response of the rat to stimuli associated with shock. In Exp 1, both chlordiazepoxide (librium) and diazepam (valium) interfered wih extinction in a dose-dependent manner as indicated by freezing during an undrugged test. Further results with chlordiazepoxide suggested that the effect depended on the drug's specific combination with extinction and that it occurred even though the extinction procedure otherwise eliminated fear completely (Exp 2). Repeated preexposure to the drug, and the development of partial tolerance to its sedative effects, did not weaken the interference effect (Exp 3). Other evidence suggested that the drug signaled or retrieved extinction instead of disrupting learning or consolidation (Exp 4). The results are consistent with research suggesting that extinguished fear can be "renewed" if the exteroceptive contextual stimuli are changed after extinction. Extinction combined with either unique exteroceptive or interoceptive cues may be specific to its context. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A role for α?-adrenergic receptors in extinction of conditioned fear and cocaine conditioned place preference.

Previous work has demonstrated an important role for adrenergic receptors in memory processes in fear and drug conditioning paradigms. Recent studies have also demonstrated alterations in extinction in these paradigms using drug treatments targeting β- and α2-adrenergic receptors, but little is known about the role of α?-adrenergic receptors in extinction. The current study examined whether antagonism of α?-adrenergic receptors would impair the consolidation of extinction in fear and cocaine conditioned place preference paradigms. After contextual fear conditioning, injections of the α?-adrenergic receptor antagonist prazosin (1.0 or 3.0 mg/kg) following nonreinforced context exposures slowed the loss of conditioned freezing over the course of 5 extinction sessions (Experiment 1). After cocaine place conditioning, prazosin had no effect on the rate of extinction over 8 nonreinforced test sessions. Following postextinction reconditioning, however, prazosin-treated mice showed a robust place preference, but vehicle-treated mice did not, suggesting that prazosin reduced the persistent effects of extinction (Experiment 2). These results confirm the involvement of the α?-adrenergic receptor in extinction processes in both appetitive and aversive preparations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Experimental renewal in human participants.

Two experiments with human participants are presented that differentiate renewal from other behavioral effects that can produce a response after extinction. Participants played a video game and learned to suppress their behavior when sensor stimuli predicted an attack. Contexts (A, B, & C) were provided by fictitious galaxies where the game play took place. In Experiment 1, participants who received conditioning in A, extinction in B, and testing in A showed some context specificity of conditioning during extinction and a recovery of suppression on test. Experiment 2 demonstrated recovery of extinguished responding when participants were conditioned in A, extinguished in B, and tested in C, a third, neutral context. The experiment also demonstrated that the context of extinction did not control performance by becoming inhibitory. Results are discussed in terms of mechanisms that can produce a response recovery after extinction. The experiments demonstrated a renewal effect: a response recovery that was not attributable to the contexts acting as simple conditioned stimuli and is the first work with human participants to conclusively do so. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Backward conditioning: Mediation by the context.

The information acquired in backward conditioning (i.e., outcome→cue) was assessed in 3 Pavlovian lick-suppression experiments with water-deprived rats as subjects. Experiment 1 confirmed previous research that few outcome→cue pairings made the cue into a conditioned excitor and additionally showed that massive posttraining extinction of the training context attenuated a backward-trained cue's excitatory value. Experiment 2 found that many outcome→cue pairings made the cue into a conditioned inhibitor and that the same context manipulation attenuated this inhibitory value. Experiment 3 confirmed the observations of Experiments 1 and 2 and demonstrated that these effects of context extinction were specific to backward-trained cues conditioned in the extinguished context. These results are interpreted in terms of cue→context and context→outcome associations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reinstatement of fear to an extinguished conditioned stimulus: Two roles for context.

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). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Persistence of fear-reducing behavior: Relevance for the conditioning theory of neurosis.

Provided experimental support for O. H. Mowrer's (1939) conditioning theory of neurosis. 16 female naive hooded rats were given conditioned stimulus/stimuli (CS) shock trials (fear conditioning) in one side of a 2-compartment apparatus. Then, in the absence of shock, Ss were allowed to escape fear by jumping a hurdle to a safe compartment. The hurdle-jumping response was considered to be analogous to anxiety-based symptomatic behavior indicative of psychopathology in that the performance of the response was unrelated to the receipt of further shock. All Ss learned the hurdle-jumping response, and then performance gradually declined until an extinction criterion was reached. Thus, a response instrumental in reducing fear was learned and was maintained over many trials. A subsequent single fear-conditioning trial led immediately to a high level of performance followed by gradual extinction. Findings imply that, when fear is extinguished, instrumental responding can cease even though some response strength remains; the importance for therapy of focusing on the extinction of both instrumental (symptomatic) behavior and fear is suggested. Evidence for the spontaneous recovery of fear is also provided. (41 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Expression of renewal is dependent on the extinction-test interval rather than the acquisition-extinction interval.

A recent finding suggested that when extinction occurs shortly after acquisition, renewal of an extinguished fear response (fear-potentiated startle) to a light conditioned stimulus (CS) is diminished (Myers, Ressler, & Davis, 2006). The present study attempted to extend this finding using a white-noise CS and freezing as the behavioral measure of fear. In Experiments 1A and 1B, we observed renewal whether extinction occurred 10 min or 24 hr after acquisition. In contrast, renewal was not observed if test occurred 10 min after extinction (Experiment 2). Experiment 3 demonstrated that expression of extinction at the 10-min extinction-test interval was attenuated by a pretest subcutaneous injection of the γ-aminobutyric acid (GABA) inverse agonist FG7142. These findings suggest that renewal is influenced more by the extinction-test interval than the acquisition-extinction interval. Further, the failure to see renewal 10 min after extinction suggests that there is a separate context memory that undergoes a different consolidation function than the CS-no US memory formed during extinction. Finally, the expression of extinction appears to be GABA dependent regardless of the extinction-test interval or the test context. (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)     

Timing of extinction relative to acquisition: A parametric analysis of fear extinction in humans.

Fear extinction is a reduction in conditioned fear following repeated exposure to the feared cue in the absence of any aversive event. Extinguished fear often reappears after extinction through spontaneous recovery. Animal studies suggest that spontaneous recovery can be abolished if extinction occurs within minutes of acquisition. However, a limited number of human extinction studies have shown that short interval extinction does not prevent the return of fear. For this reason, we performed an in-depth parametric analysis of human fear extinction using fear-potentiated startle. Using separate single-cue and differential conditioning paradigms, participants were fear conditioned and then underwent extinction either 10 min (Immediate) or 72 hr (Delayed) later. Testing for spontaneous recovery occurred 96 hr after acquisition. In the single cue paradigm, the Immediate and Delayed groups exhibited differences in context, but not fear, conditioning. With differential conditioning, there were no differences in context conditioning and the Immediate group displayed less spontaneous recovery. Thus, the results remain inconclusive regarding spontaneous recovery and the timing of extinction and are discussed in terms of performing translational studies of fear in humans. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spontaneous recovery of extinguished fear responses deepens their extinction: A role for error-correction mechanisms.

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. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differential contribution of amygdala and hippocampus to cued and contextual fear conditioning.

The contribution of the amygdala and hippocampus to the acquisition of conditioned fear responses to a cue (a tone paired with footshock) and to context (background stimuli continuously present in the apparatus in which tone–shock pairings occurred) was examined in rats. In unoperated controls, responses to the cue conditioned faster and were more resistant to extinction than were responses to contextual stimuli. Lesions of the amygdala interfered with the conditioning of fear responses to both the cue and the context, whereas lesions of the hippocampus interfered with conditioning to the context but not to the cue. The amygdala is thus involved in the conditioning of fear responses to simple, modality-specific conditioned stimuli (CS) as well as to complex, polymodal stimuli, whereas the hippocampus is only involved in fear conditioning situations involving complex, polymodal events. Findings suggest an associative role for the amygdala and a sensory relay role for the hippocampus in fear conditioning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)