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)     

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)     

Inhibition as a "slave" process: Deactivation of conditioned inhibition through extinction of conditioned excitation.

In 4 experiments with 176 male albino Sprague-Dawley rats, a conditioned-suppression paradigm was used to investigate why a conditioned inhibition (CS–) does not extinguish when presented alone. Exp I assessed the role of blocking by excitatory contextual cues and/or an evoked representation of the conditioned excitor (CS+), which had been nonreinforced in conjunction with the CS–. When the CS+ and context were extinguished prior to presentations of the CS– alone, the CS– showed a retardation effect, reflecting latent inhibition, because no inhibition was detected in controls for which presentation of the CS– alone had been omitted. Exp II showed that the loss of conditioned inhibition (CI) was due to excitatory extinction and not to time since conditioning. When excitation was reconditioned to the extinguished CS+ (Exp I) or to a novel CS in the same context (Exp II), CI was restored. Exps III and IV evaluated whether the maintenance of CI depended on excitation that was generic in form or associatively tied to the training context. Results indicate no loss of CI when groups received CS+ extinction in that context, with concomitant presentations in a different context of the UCS by itself, for a novel CS, or correlated either positively or negatively with the original CS+. Overall findings suggest that CI is dependent on excitation: When excitation is extinguished, CI is deactivated; when excitation is reconditioned to the original or a new CS+ in the same or a different context, CI is restored. (41 ref) (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Selective hippocampal lesions abolish the contextual specificity of latent inhibition and conditioning.

The contextual specificity of the CR and latent inhibition (LI) was examined in rats with selective hippocampal lesions. Acquisition of the CR to a novel CS was equally rapid in control and hippocampal rats (Exps 1 and 2), and CS preexposure disrupted acquisition (i.e., produced LI) to an equal extent in both groups (Exp 2). In control Ss, however, the CR established in one context transferred incompletely to a 2nd context (Exp 1), and LI was attenuated when CS preexposure and conditioning occurred in different contexts (Exp 3). This context specificity of the CR and LI was not apparent in hippocampal rats; the CR and LI transferred readily from one context to another. In addition, hippocampal rats were impaired in a spatial learning task (Exp 2) but were unimpaired in learning a Pavlovian contextual discrimination (Exp 3). Results suggest that a common contextual retrieval process underlies the contextual dependence of the CR and of LI and that this process is mediated by the hippocampus. (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)     

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)     

Analysis of the associative and occasion-setting properties of contexts participating in a Pavlovian discrimination.

In 3 conditioned suppression experiments with 64 male Wistar rats, contextual control of performance to a conditioned stimulus (CS) was generated by alternating CS–unconditioned stimulus (UCS) pairings in Context A with CS presentations alone in Context B. Suppression to the CS during discrimination training and during tests of the CS in a 3rd context suggested that Contexts A and B had both acquired an ability to modulate performance. Whether the contexts modulated behavior through their direct associations with the UCS or through their abilities to occasion-set the CS–UCS relation was explored. There was no evidence of direct context–UCS associations in either context. Repeated extinction exposures to Context A following discrimination training did not affect its ability to modulate CS performance. Excitatory conditioning of Context B, however, abolished its ability to modulate. It is suggested that demonstrable context–UCS associations are not necessary for the contextual control of CS performance and that although the parallel is not perfect, contexts share several critical properties with stimuli that occasion-set CS–UCS relations. The possible role of configural conditioning is discussed. (54 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of exposure to conditioned stimulus and control of its termination in the extinction of avoidance behavior.

Describes 2 experiments in which, following signaled shuttle box avoidance training, a total of 52 female Fischer344 rats were exposed to the conditioned stimulus (CS) during no-shock treatment trials and subsequently tested during extinction trials in which shock was also absent. In Exp I, Ss that could control the termination of the CS during treatment responded significantly more often during extinction than yoked partners that received the same pattern and duration of CS exposure but could not control its termination. Exp II revealed that the probability of responding during extinction was a decreasing function of the duration of CS exposure during treatment. Thus, in the absence of shock, both lack of control over CS termination and increasing CS exposure each independently facilitated the weakening of well-established avoidance responses. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of the rat hippocampal system in several effects of context in extinction.

The effect of fornix lesions on some effects of manipulating the context on performance in extinction were studied. In renewal, subjects' responding to an extinguished CS recovered when the CS was presented in the context in which it had been conditioned after extinction in a different context. In reinstatement, it recovered when the CS was tested after independent presentation of the unconditioned stimulus (UCS; an effect mediated by contextual conditioning.) In spontaneous recovery, it recovered after the passage of time, that is, when the CS was tested in a new temporal context. In the conditioned suppression method, fornix lesions had no effect on conditioning, extinction, renewal, or spontaneous recovery; however, they abolished the reinstatement effect. The results suggest that the hippocampal system may be important in the formation of context–UCS associations, but not in other types of learning about the context. (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)     

Effect of signaling intertrial unconditioned stimuli in autoshaping.

Context–UCS associations have been suggested as the mediator of the response decrement that occurs when extra UCSs are added to the intertrial intervals (ITIs) of a standard Pavlovian conditioning situation. The present autoshaping experiments were concerned with the effect of signaling those extra UCSs, since such signaling might be expected to lessen their ability to condition the context. In Exp I, 16 female Carneaux pigeons were trained in Skinner boxes before receiving pretraining with the CS to be used as the signal of the ITI UCSs. During the main training, Ss were given autoshaping with a keylight CS. Exp II used a tone CS with 31 Ss. Results show that signaling the ITI UCSs did reduce their detrimental effects in responding to the CS. To determine whether that reduction was due to an impact of signaling on the target-CS/UCS association or on performance to the target-CS, Exp III examined responding to differentially trained CSs in a common context, as well as responding to identically trained CSs in differentially trained contexts with 32 Ss. More responding occurred to the CS trained with signaled, as compared with unsignaled, ITI UCSs; further, there was more responding to that CS in the more highly valued context. Results suggest that contextual value does interact with CS–UCS learning and may also affect performance to the CS. (42 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of contingency violations on the extinction of a conditioned fear inhibitor and a conditioned fear excitor.

In 4 experiments, 192 male Holtzman and Sprague-Dawley rats were used in a conditioned-suppression paradigm to assess the effects of contingency variations on responding to a conditioned stimulus (CS) inhibitor (CS–) and a conditioned stimulus excitor (CS+). In Exp I, various unconditioned stimulus/stimuli (UCS) frequencies were equated across the presence and absence of a CS– in the context of either background cues (continuous-trial procedure) or an explicit neutral event (discrete-trial procedure). With both procedures, a CS-alone treatment enhanced inhibition, whereas treatments involving 50 or 100% reinforcement for the CS– eliminated inhibition without conditioning excitation to that CS. The latter outcome also occurred in Exp II, with discrete-trial training equating considerably reduced UCS frequencies for the presence and absence of the CS–. In further evidence that inhibition was eliminated without conditioning excitation to the CS–, Exp III showed that a novel CS did not acquire excitation when 25, 50, or 100% reinforcement was equated across the presence and absence of that CS in the context of a discrete-trial event. Using the procedures of Exp I, Exp IV showed that a CS+ was extinguished by a CS-alone treatment but was substantially maintained by treatments involving 50 or 100% uncorrelated reinforcement. These effects for a CS+ and a CS– implicate CS–UCS contiguity, rather than contingency, as the factor determining the extinction of a CS. (33 ref) (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)     

Disruptive effects of posttraining perirhinal cortex lesions on conditioned fear: Contributions of contextual cues.

Lesions placed in the rostral perirhinal cortex (rPRh) after fear conditioning interfere with the expression of conditioned fear responses elicited by auditory and visual conditioned stimuli when these stimuli are presented in a context that differs from the conditioning context. The present study examined whether lesions of the rPRh have similar effects when animals are tested in the conditioning context. Two days after male rats received classical fear conditioning, involving the pairing of an auditory CS with footshock, bilateral electrolytic lesions were produced in the rPRh. Five days later conditioned freezing behavior was measured during a 60-s exposure to the CS in a novel context and then 1 hr later in the conditioning context. There were 3 major findings: rPRh-lesioned Ss froze significantly less than controls to the CS in the novel context, thus confirming previously reported findings. rPRh-lesioned Ss also froze less than controls to the CS in the conditioning context, but froze significantly more to the CS in the conditioning than in the novel context, suggesting that at least part of the deficit in the novel context is due to the absence of contextual cues. Ss with rPRh lesions froze significantly less than controls to the conditioning context itself.… (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)     

Pavlovian second-order conditioned analgesia.

Three experiments, with 118 Sprague-Dawley rats, assessed conditioned analgesia in a Pavlovian 2nd-order conditioning procedure by using inhibition of responding to thermal stimulation as an index of pain sensitivity. In Exp I, Ss receiving 2nd-order conditioning showed longer response latencies during a test of pain sensitivity in the presence of the 2nd-order conditioned stimulus (CS) than Ss receiving appropriate control procedures. Exp II found that extinction of the 1st-order CS had no effect on established 2nd-order conditioned analgesia. Exp III evaluated the effects of post 2nd-order conditioning pairings of subcutaneous morphine sulfate (10–20 mg/kg) and the shock unconditioned stimulus/stimuli (UCS). Ss receiving paired morphine–shock presentations showed significantly shorter response latencies during a hot-plate test of pain sensitivity in the presence of the 2nd-order CS than did Ss receiving various control procedures; 2nd-order analgesia was attenuated. Data extend the associative account of conditioned analgesia to 2nd-order conditioning situations and are discussed in terms of the mediation of both 1st- and 2nd-order analgesia by an association between the CS and a representation or expectancy of the UCS, which may directly activate endogenous pain inhibition systems. (52 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mechanisms underlying retarded emergence of conditioned responding following inhibitory training: Evidence for the comparator hypothesis.

The comparator hypothesis posits that conditioned responding is determined by a comparison at the time of testing between the associative strengths of the conditioned stimulus/stimuli (CS) and stimuli proximal to the CS at the time of conditioning. The hypothesis treats all associations as being excitatory and treats conditioned inhibition as the behavioral consequence of a CS that is less excitatory than its comparator stimuli. Conditioned lick suppression by rats was used to differentiate 4 possible sources of retarded responding to an inhibitory CS. These include habituation to the unconditioned stimulus/stimuli (UCS), latent inhibition to the CS, blocking of the CS-UCS association by the conditioning context, and enhanced excitatory associations to the comparator stimuli. Prior research has demonstrated the 1st 3 phenomena. Therefore, we employed parameters expected to highlight the 4th one—the comparator process. In Exp I, our negative contingency training produced a conditioned inhibitor that passed inhibitory summation and retardation tests. In Exp II we found transfer of retardation from an inhibitory CS to a novel stimulus when the location where retardation-test training occurred was excitatory. In Exp III, extinction of the conditioning context attenuated retardation regardless of whether extinction occurred before or after the CS-UCS pairings of the retardation test. Exp IV demonstrated that habituation to the UCS did not contribute to retardation in the present case. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Associative effects of US preexposure: Modulation of conditioned responding by an excitatory training context.

Conducted 2 experiments with 120 naive Sprague-Dawley rats to examine factors that contribute to retarded emergence of conditioned responding to a conditioned stimulus/stimuli (CS) trained in a context in which unsignaled unconditioned stimulus/stimuli (UCS) had previously been administered. In both experiments, water-deprived Ss were used in a conditioned lick suppression task to measure the conditioned response (CR) elicitation potential of the CS and the training context. From Exp I, it was determined that nonreinforced exposure to the excitatory context after UCS preexposure and prior to CS–UCS pairings in that context eliminated the CR deficit observed on a subsequent test of the CS. From Exp II, it was determined that the recovery induced by contextual deflation after CS training was specific to deflation of the context in which the CS was trained as opposed to another excitatory context. (28 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A retrieval cue for extinction attenuates response recovery (renewal) caused by a return to the conditioning context.

When conditioning and extinction are conducted in different contexts, a return to the conditioning context causes a renewal of conditioned responding. The results of 4 experiments with rats in an appetitive conditioning preparation suggest that renewal results from a failure to retrieve extinction outside the extinction context. Presentation of a cue from extinction during renewal testing attenuated the renewal effect; attenuation depended on the cue's correlation with extinction. On its own, the cue did not elicit responding, suggesting it was not a conditioned excitor; it also failed tests for conditioned inhibition. The authors propose that it worked by retrieving a memory of extinction. The findings parallel previous results with spontaneous recovery and are thus consistent with the view that renewal and spontaneous recovery result from a common mechanism. (PsycINFO Database Record (c) 2010 APA, all rights reserved)