Exposure techniques in the reduction of fear: A comparative review of the procedure in animals and humans

Successful implementation of cooperative handling eliminates the need for restraint in a complex non-human primate disease model

BACKGROUND

Streptozotocin-induced diabetic non-human primates are used to study efficacy and safety of innovative immunosuppression after islet transplantation. We implemented a training program for medical management of a chronic disease state.

METHODS

Cooperation with hand feeding and drinking, shifting, and limb presentation were trained utilizing predominately positive but also negative reinforcement in 52 animals compared with 28 macaques subjected to conventional physical and/or chemical restraint. The success and timing of behavior acquisition was evaluated in a representative subset of 14 animals.

RESULTS

Over 90% of animals were successful in behavior acquisition. Programmatically this resulted in complete elimination of chair restraint and negligible requirement for sedation. About half of the trained animals had no-to-moderate thymic involution, indicative of a substantial reduction in stress.

CONCLUSION

Cooperative handling enhances animal well-being. This contributes to validity of scientific results and eliminates model-induced confounding that can obstruct interpretation of safety and efficacy data.

Classical Conditioning: Still Going Strong

This paper summarizes developments in the field of classical conditioning. Attention is paid to four common misconceptions of what is classical conditioning. First, classical conditioning does not ensue as a simple result of temporal pairing of conditioned and unconditioned stimuli. Rather, conditioned reacting occurs if and to the degree that the subject is able to predict the occurrence of one stimulus from the presence of another one. Second, what is learned during classical conditioning is not necessarily a response to a cue, but rather a probabilistic relationship between various stimuli. Third, classical conditioning is not only manifested in responses mediated by the autonomic nervous system, but also in immunological parameters, in motoric behaviour and in evaluative judgments. Fourth, the nature of the conditioned and the unconditioned stimulus is (often) not a matter of indifference: particular combinations of CS and US produce more powerful conditioning effects than do other combinations. In the second part of the paper, the potential relevance of these developments is illustrated. Discussions are included about anxiety, addictions and food aversions/conditioned nausea.

Effects of d-cycloserine on extinction of learned fear to an olfactory cue

D-cycloserine (DCS), a partial NMDA receptor agonist, facilitates extinction of learned fear in rats and has been used to treat anxiety disorders in clinical populations. However, research into the effects of DCS on extinction is still in its infancy, with visual cues being the primary fear-eliciting stimuli under investigation. In both human and animal subjects odors have been found to associate strongly with aversive events. Therefore, this study examined the generality of the effects of DCS on extinction by testing odor cues. Sprague-Dawley rats were conditioned and extinguished to an odor using varying parameters, injected with either saline or DCS (15 mg/kg) following extinction, and then tested for a freezing response 24 h later. Experiment 1 demonstrated that after 3 odor-shock pairings, rats did not display short-term extinction and DCS had no effect on long-term extinction. Experiment 2 demonstrated that after 3 odor-noise pairings, rats displayed significant short-term extinction and DCS significantly facilitated long-term extinction. Following 2 odor-shock pairings in Experiment 3, half the rats displayed short-term extinction ("extinguishers") and half did not ("non-extinguishers"). DCS facilitated long-term extinction in the "extinguishers" condition but not in the "non-extinguishers" condition. In Experiment 4, following 2 odor-shock pairings and an extra extinction session, DCS had a significant facilitatory effect on long-term extinction. Thus, extinction of freezing to an odor cue was facilitated by systemic injections of DCS, but only when some amount of within-session extinction occurred prior to injection.

Effects of multiple exposures to d-cycloserine on extinction of conditioned fear in rats

Previous research has shown that an acute, post-training injection of D-cycloserine (DCS) facilitates extinction of conditioned fear in rats; however, the effects of multiple exposures to DCS in this situation are not known. In Experiment 1, rats were conditioned (light-shock pairings) and 24 h later given six extinction (light-alone) trials followed by an injection of DCS (15 mg/kg) or saline. The next day, all rats were tested for light-elicited freezing. In Experiment 2, the effect of DCS on extinction was tested in the same manner, except that rats were pre-exposed to DCS (0, 1, or 5 injections) just prior to conditioning. In Experiment 3, rats received five pre-exposures of DCS but conditioning occurred either 2 or 28 days after the last pre-exposure. The results showed that DCS facilitated extinction of conditioned freezing to the light CS when no drug pre-exposure had occurred, but pre-exposure to DCS just prior to conditioning disrupted the facilitation of extinction effect. When 28 days were interposed between pre-exposure and conditioning, the facilitatory effects of DCS on extinction were restored. These findings suggest that DCS has significant clinical value but that behavioral desensitization may occur with multiple exposures; however, desensitization is not permanent and is reduced by the passage of time.

Effects of relaxation training on fear and arousal during in vivo exposure to a caged snake among DSM-III-R simple (snake) phobics

Eight pairs of DSM-III-R snake phobic subjects (Ss) were exposed to a caged snake while seated in front of a package-conveyor apparatus during eight 4-minute trials. Heart rates and skin-conductance levels were recorded before and during each of the eight trials. Self-reports of fear were obtained after each trial. One S in each pair controlled the conveyor on alternating trials. One subject (S) in each pair had received a representative regimen of relaxation training beforehand. Heart-rate decreased more in Ss controlling the conveyor than in their yoked partners. Ss who had received relaxation training showed lower heart-rate change, lower skin-conductance change, and lower self-reports of fear after the exposure trials. Relaxed Ss also moved the snake closer to themselves than did unrelaxed subjects on some trials.

Control and attention during exposure influence arousal and fear among insect phobics

Heart beats, skin conductance, and subjective fear levels were recorded among eight pairs of DSM-III-R spider-phobic subjects (Experiment 1) and among eight pairs of DSM-III-R cockroach-phobic subjects (Experiment 2) who were exposed simultaneously to an approaching specimen during eight 4-minute trials. Control over the approach of the specimen alternated between subjects over trials. On different trials, both subjects were instructed either to attend closely to the features of the specimen or to attend closely to their bodily fear reactions. Among spider-phobic subjects (Experiment 1), Self-Control over the specimen produced higher skin conductance during exposure than did Partner-Control over the specimen; instructions to attend closely to the features of the specimen produced higher skin-conductance than did instructions to attend closely to one's bodily fear reactions. Among cockroach-phobic subjects (Experiment 2), Self-Control over the specimen produced higher skin conductance and higher self-reported fear than did Partner-Control over the specimen during the early exposures. Instructions to attend closely to the specimen produced higher skin conductance and higher self-reported fear throughout the experiment and higher heart rates early during the experiment than did instructions to attend to one's bodily reactions. Empirical generalizations based on these data are intended as contributions toward a fund of experimental information that, in due course, will be used to conceptualize the means by which exposure to feared stimuli leads to fear reduction.

Feather picking disorder and trichotillomania: an avian model of human psychopathology

Animal models of psychopathology have been extremely valuable in conceptualizing various human disorders. The human condition known as trichotillomania (compulsive hair pulling) has considerable similarities with an avian disorder called feather picking, with respect to analogous behavior, proposed etiologies, evoking cues, response to behavior therapy, and response to pharmacological treatments based on serotonin re-uptake inhibitors. We suggest that feather picking disorder has the potential to be a useful animal model of trichotillomania, and lends itself to studies on the experimental psychopathology of compulsive hair pulling.

Extinction of a conditioned emotional response: massed and distributed exposures

Using the lick-suppression methodology of Jacobs, Buttrick & Kennedy (Pavlovian Journal of Biological Science, 23, 29-34, 1988), a conditioned emotional response (CER) was established in 24 rats using off-the-baseline pairings of a light (the conditional stimulus) and brief footshock (the unconditioned stimulus). Following conditioning, the rats were assigned to one of three extinction groups differing in whether they received massed or distributed off-the-baseline exposure to the conditional stimulus. The effects of differential treatment were assessed on-the-baseline on test days, when the extinction of the CER was monitored. Rats receiving a single, long exposure to the conditional stimulus showed greater resistance to extinction than the rats in the distributed groups. They also showed a difference pattern of CER extinction. The results were discussed and compared to similar studies that have explored the massed vs distributed dimension, both in CER and avoidance-extinction (using response prevention or flooding). The relation of animal studies to parallel human studies using exposure therapy was also discussed.

The derailment of behavior therapy: a tale of conceptual misdirection

Forty years ago it was shown that neuroses are persistent unadaptive anxiety response habits that can be systematically overcome by deconditioning procedures collectively known as behavior therapy. Indispensable to behavior therapy is behavior analysis--detailed and accurate specification of the antecedents of the individual's neurotic patterns. In recent years, the behavior therapy movement has been infiltrated by two alien orientations--"exposure therapy" and cognitivism--which repudiate conditioning theory and dispense with the characteristic behavior analysis. By claiming to be more effective, the alien approaches have induced widespread abandonment of the conditioning model. In fact, outcomes have not been improved by the alien methodologies, and in many cases have become worse. Also, no viable theory of change has been proposed in place of conditioning. The result is an amorphous eclecticism to which psychoanalysis and primal scream could readily be added. Some first steps are suggested towards restoring conditioning principles to their central role in the behavior therapy field.

Veterinary use of exposure techniques in the treatment of phobic domestic animals

Exposure techniques as a treatment for human phobias are reviewed, as well as exposure's use in the extinction of avoidance behavior in laboratory animal studies. A third arena in which exposure is employed is reconsidered--in the veterinary treatment of phobic domestic animals. Veterinary use of exposure is illustrated, and the advantages and disadvantages of the veterinary study of exposure are discussed.