Mark E. Bouton

A modern learning theory perspective on the etiology of panic disorder

Several theories of the development of panic disorder (PD) with or without agoraphobia have emerged in the last 2 decades. Early theories that proposed a role for classical conditioning were criticized on several grounds. However, each criticism can be met and rejected when one considers current perspectives on conditioning and associative learning. The authors propose that PD develops because exposure to panic attacks causes the conditioning of anxiety (and sometimes panic) to exteroceptive and interoceptive cues. This process is reflected in a variety of cognitive and behavioral phenomena but fundamentally involves emotional learning that is best accounted for by conditioning principles. Anxiety, an anticipatory emotional state that functions to prepare the individual for the next panic, is different from panic, an emotional state designed to deal with a traumatic event that is already in progress. However, the presence of conditioned anxiety potentiates the next panic, which begins the individuals spiral into PD. Several biological and psychological factors create vulnerabilities by influencing the individuals susceptibility to conditioning. The relationship between the present view and other views, particularly those that emphasize the role of catastrophic misinterpretation of somatic sensations, is discussed.

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

Four conditioned suppression experiments examined the influence of contextual stimuli on the rats fear of an extinguished conditioned stimulus (CS). When rats received pairings of a CS with shock in one context and then extinction of the CS in another context, fear of the CS was renewed when the CS was returned to and tested in the original context (Experiments 1 and 3). No such renewal was obtained when the CS was tested in a second context after extinction had occurred in the conditioning context (Experiment 4). In Experiment 2, 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 the rats 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. Moreover, there was no evidence that contextual inhibition developed during extinction. The 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.

Contextual control of the extinction of conditioned fear

Abstract Rats received 15 pairings of a CS and shock in one context, and then a series of CS-alone trials in a second context. Even though this extinction procedure produced a complete loss of conditioned suppression, when the animals were returned to the site of original conditioning, suppression was renewed to a level comparable to that of animals that had not undergone extinction. Controls indicated that the renewed suppression was not due solely to pseudoconditioning, suggesting that the CS-US association had survived extinction. Renewed suppression was also demonstrated in a third context that was never associated with shock. Loss of suppression did not necessarily depend upon inhibitory conditioning of the extinction context. The data suggest that extinction of conditioned fear is specific to the context in which it occurs. They also suggest the possibility that animals might discriminate episodes in which a CS is reinforced and nonreinforced independently of the excitatory or inhibitory status of cues, like contextual stimuli, that are coincidentally present during those episodes.

Contextual and temporal modulation of extinction : Behavioral and biological mechanisms

Extinction depends, at least partly, on new learning that is specific to the context in which it is learned. Several behavioral phenomena (renewal, reinstatement, spontaneous recovery, and rapid reacquisition) suggest the importance of context in extinction. The present article reviews research on the behavioral and neurobiological mechanisms of contextual influences on extinction learning and retrieval. Contexts appear to select or retrieve the current relationship of the conditional stimulus (CS) with the unconditional stimulus (US), and they are provided by physical background cues, interoceptive drug cues, emotions, recent trials, and the passage of time. The current article pays particular attention to the effects of recent trials and trial spacing. Control of fear extinction by physical context involves interactions between the dorsal hippocampus and the lateral nucleus of the amygdala. This interaction may be mediated by gamma-aminobutyric acid (GABA)-ergic and adrenergic mechanisms.

Role of conditioned contextual stimuli in reinstatement of extinguished fear.

If the unconditioned stimulus (US) is presented independently of the conditioned stimulus (CS) following extinction, the conditioned response may be reinstated to the CS. Three experiments are reported that suggest that reinstatement is mediated by conditioning to contextual stimuli that are present during both US presentation and testing. Shocks presented to rats following the extinction of conditioned suppression reliably reinstated suppression to the CS, but only when they were presented in the context in which testing was later to occur. Reinstatement was also reversed by extinguishing fear to the context through nonreinforced exposure to the context between shock presentation and testing. Reinstatement was obtained in these experiments in spite of procedures that have been used in the past to minimize the influence of context conditioning. Moreover, fear of the context was never detected directly by depressed bar-press rates in the absence of the CS. The results do not support the hypothesis that reinstatement results from an increment in the strength of a memory of the US that has been weakened during extinction. Problems inherent in controlling and detecting levels of context conditioning that may influence behavior toward nominal CSs are discussed.

Hippocampus and context in classical conditioning

Recent evidence suggests that contextual learning encompasses a variety of changes in learning and performance processes. Only some of these changes depend on the hippocampus. Specialized functions proposed for the hippocampus in contextual learning include the construction and consolidation of contextual memory representations, incidental contextual learning, and inhibitory contextual learning.

Sources of relapse after extinction in Pavlovian and instrumental learning

Abstract Extinction may be related to therapeutic procedures designed to eliminate unwanted thoughts, emotions, or behaviors. This article reviews animal learning research which suggests that extinction does not erase the original learning, but rather makes behavior especially sensitive to the background, or context, in which it occurs. Context-dependence of responding is evident after extinction in both Pavlovian and instrumental (operant) learning. In either case, memories of conditioning and extinction are both retained through extinction, and are available for retrieval by appropriate retrieval cues. When the context promotes retrieval of extinction, extinction performance is observed. But when the context is changed, or when the current context promotes retrieval of conditioning, conditioning performance is often restored. These effects are produced by contexts provided by stimuli as diverse as physical environments, reinforcer after-effects, drug states, emotions, and the passage of time. The results have implications for relapse, and its prevention, following therapy.

Conditioning, remembering, and forgetting

Theories of learning and of memory have been artificially separated for many years. In this article it is argued that the separation should be abandoned. Remembering and forgetting play an important role in simple conditioning experiments. For example, conditioned performance can readily recover after extinction because extinction is susceptible to forgetting. Memory itself involves the kind of associative learning that conditioning experiments are designed to investigate (e.g., conditioning experiments provide insight into the mechanisms of memory retrieval). Learning, remembering, and forgetting all occur within the same biological context; their adaptive functions are therefore intertwined. Then together, they shed light on some of the mechanisms of clinical relapse

Conditioned fear assessed by freezing and by the suppression of three different baselines

Rats received either forward or backward pairings of an auditory CS and shock. They were then tested for conditioned suppression to the CS while barpressing for food, licking a sucrose solution, or being spontaneously active. Behavior was simultaneously observed using a time-sampling method. In each case, forward-conditioned animals exhibited more freezing than controls, and freezing was reliably correlated with suppression of the baseline. These results suggest that the different loss-of-baseline measures of aversive conditioning reflect the amount of defensive behavior evoked by the CS. They also suggest the utility of freezing as an index of conditioning. Freezing assayed by the time-sampling method was comparable to the more conventional indices of conditioning in sensitivity to the effects of conditioning.

Renewal of extinguished responding in a second context.

In three experiments with rats, we demonstrated that a conditioned response that is learned and extinguished in one context (Context A) can be renewed when the conditioned stimulus (CS) is tested in a second context (Context B). In Experiments 1 and 3, the effect was observed in conditioned suppression; in Experiment 2, it was produced in appetitive conditioning. The result occurs when Contexts A and B are equally familiar, equally associated with reinforcement, or equally associated with both reinforcement and nonreinforcement. The results extend the range of conditions known to produce the renewal effect, and they are consistent with the view that retrieval of extinction depends more on the context than does retrieval of conditioning.