Effects of temporal placement of response prevention on extinction of avoidance in rats

Two experiments investigated the effects of prior extinction trials upon the effectiveness of response prevention procedures (flooding) in facilitating extinction of avoidance in rats. The results showed that both prior CS only extinction trials and response prevention independently hastened extinction and that response prevention is enhanced if prior extinction has already taken place. The results were interpreted as being consistent with a relaxation interpretation of extinction of avoidance behavior providing a ‘distraction’ or ‘attention shift’ factor is incorporated into theory.     

Effects of progesterone and nesting materials on response prevention and extinction of avoidance in rats

Female rats received either progesterone or saline injections prior to learning a simple one-way avoidance response. During a 10-min response prevention procedure half of the animals in each group had nesting material present while the remaining rats did not. The availability of nesting material during response prevention hastened extinction while progesterone injections significantly increased the frequency of nesting activities during response prevention but did not affect rate of extinction. The availability of nesting materials increased the frequency of standing but reduced the frequency of crouching. The results were discussed in terms of the role of ethological displacement activities during response prevention as well as the role of ‘relaxational’ activities as discussed by Baum and Denny.     

Using drugs to modify the effect of response prevention on avoidance extinction

Amobarbital and chlordiazepoxide were administered during avoidance response prevention and the effect evaluated in the nondrugged state in a subsequent test for avoidance extinction. It was found that Ss administered 15 mg/kg and 30 mg/kg amobarbital, and 30 mg/kg chlordiazepoxide during response prevention differed significantly from the control Ss in extinction performance. Rather than showing either reduced avoidance performance or no difference with the nondrugged Ss, the Ss drugged during response prevention showed increased avoidance performance in the subsequent test of avoidance extinction. That is, preventing avoidance responding under a drugged (versus nondrugged) state produced increased resistance to extinction of the avoidance response.     

The development and the extinction of hyperthermia induced by conditioned avoidance behavior in rats

Hyperthermia was observed at the end of each conditioning session in rats trained to avoid electric shocks by jumping on a platform. The temperature rise was also observed after the conditioned behavioral response was well established and was elicited even in the absence of shocks. There was no tendency for the hyperthermia to diminish over the course of nine extinction sessions.     

On insirumental response interaction as explaining the influences of Pavlovian CSs upon avoidance behavior

The finding that Pavlovian signals for food or shock influence avoidance responding might be explained either by interaction of conditioned central mediational states or interaction of learned instrumental responses. Using three groups of dogs, the two hypotheses were pited one against the other in a three-stage transfer-of-control experiment. In the initial conditioning phase, tones were established as signals for food, shock, or neither; additionally the tones also cued a common instrumental response. Following avoidance training, the tone was tested for its influence upon avoidance. If the lone had signaled food, avoidance was suppressed; if shock, avoidance was facilitated; if neither, avoidance was unaffected. This was interpreted as supporting the hypothesis that interaction of central states mediates the transfer-of-control.     

Effects of naloxone on acquisition and extinction of jump-up avoidance behavior in rats

Two experiments were carried out to assess the effects of the opioid antagonist, naloxone, on the acquisition and extinction of shock avoidance by rats in the jump-up apparatus. In Experiment 1 naloxone pretreatment facilitated acquisition but had no effect on extinction of avoidance behavior. In the second experiment the effect of naloxone on acquisition was replicated and in addition, it was shown that naloxone enhanced freezing when a response prevention or flooding procedure was introduced. Again naloxone failed to alter the course of extinction, nor did it interact with the effects of flooding which, by itself, facilitated extinction. The results suggest that naloxone's effects are limited to increasing the functional intensity of the US, and provide further support for the dissociation between extinction of avoidance behavior and other indices of fear.     

ACTH produces long-lasting recovery following partial extinction of an active avoidance response

Recent data suggest that ACTH administration produces recovery of an extinguished passive avoidance response at an unusually long injection-to-test interval. The present experiment sought to explore further the durability of recovery by examining the effect of ACTH following extinction of one-way active avoidance. Adult rats were injected with 16 IU ACTH, an equivalent volume of the ACTH vehicle gel, or saline 48 h after a previously learned active avoidance response was partially extinguished. Different groups from each treatment condition were tested 15 min, 24 h, or 7 days after injection. ACTH improved avoidance performance at all injection-to-test intervals relative to saline and vehicle gel injected controls. These data indicate that unlike reversal of other types of performance decrements, in which the effect of ACTH appears to be transient, administration of the hormone following an extinction treatment can produce enduring improvement of avoidance performance.     

Pavlovian conditioned inhibition of fear during shuttlebox avoidance behavior

Three experiments explored the development and function of conditioned inhibition of fear during the acquisition and maintenance of shuttlebox avoidance behavior. The development of inhibition to an exteroceptive feedback stimulus was found to be a function of the number of successive avoidance responses to which the animal had been trained and of the duration of the intertrial interval, a parameter shown also to affect the rate of acquisition of avoidance learning. Master animals who learned the instrumental avoidance response, and yoked animals who did not, showed equivalent inhibitory fear conditioning in each experiment. The results of one experiment suggest that conditioned inhibition plays no important role in “protecting” fear conditioned to the discrete warning signal during avoidance maintenance. These data indicate that feedback stimuli develop their inhibitory properties by a Pavlovian process and that certain aspects of their function may, therefore, be readily understood within the framework of mediational two-process learning theory.     

Passive avoidance behavior in rats after electroconvulsive shock: facilitative effect of response retardation.

Rats were trained in a one-trial passive avoidance task and then were submitted to electroconvulsive shock (ECS) or to sham ECS. Twenty-four hours later they were tested for retention, with the door opened either immediately or 30 sec after the beginning of the test. Rats initially forced to avoid for 30 sec continued to avoid for the entire test, but the others had the usual low step-through latencies seen with ECS-treated animals. Activity measures for those animals stepping through differentiated groups having received footshock from those not having footshock and ECS. A retest 5--10 min later showed "recovery" in the amnestic animals and continued avoidance behavior for those that avoided on the first test. Results are taken as evidence that ECS effects are not on memory storage but on the capacity of the animal to organize information effectively and quickly in order to produce an adaptive response.     

Spontaneous recovery after extinction of the conditioned proboscis extension response in the honeybee

In honeybees, the proboscis extension response (PER) can be conditioned by associating an odor stimulus (CS) to a sucrose reward (US). Conditioned responses to the CS, which are acquired by most bees after a single CS-US pairing, disappear after repeated unrewarded presentations of the CS, a process called extinction. Extinction is usually thought to be based either on (1) the disruption of the stored CS-US association, or (2) the formation of an inhibitory "CS-no US" association that is better retrieved than the initial CS-US association. The observation of spontaneous recovery, i.e., the reappearance of responses to the CS after time passes following extinction, is traditionally interpreted as a proof for the formation of a transient inhibitory association. To provide a better understanding of extinction in honeybees, we examined whether time intervals during training and extinction or the number of conditioning and extinction trials have an effect on the occurrence of spontaneous recovery. We found that spontaneous recovery mostly occurs when conditioning and testing took place in a massed fashion (1-min intertrial intervals). Moreover, spontaneous recovery depended on the time elapsed since extinction, 1 h being an optimum. Increasing the number of conditioning trials improved the spontaneous recovery level, whereas increasing the number of extinction trials reduced it. Lastly, we show that after single-trial conditioning, spontaneous recovery appears only once after extinction. These elements suggest that in honeybees extinction of the PER actually reflects the impairment of the CS-US association, but that depending on training parameters different memory substrates are affected.     

Pavlovian processes and response competition as determinants of avoidance response-prevention effects

Two experiments investigated the facilitation of avoidance extinction by exposure to lengthy (5-sec) shock during avoidance response prevention. In Experiment 1, animals exposed to light only or to light-shock pairings during response prevention showed equal facilitation of extinction relative to shock-only animals or to animals receiving no response prevention. Preshock rearing, directly antagonistic to the avoidance response, developed for shocked animals during response prevention and persisted during extinction for light-shock animals. Immediately before extinction, half of each group was permitted a single escape from a light-shock compound by means of the response previously required for avoidance. The only effect was upon the extinction performance of light-shock animals. Rearing was eliminated and extinction responding increased to a level far above that for any of the other animals. Experiment 2 demonstrated that the shock-only treatment affected the extinction performance and rearing of nonescape and escape animals in a manner entirely equivalent to the effects of the light-shock treatment of Experiment 1, provided stimulus conditions (light absent) were the same for all experimental phases. Thus, lengthy shock during avoidance response prevention simultaneously leads to the acquisition of competing behavior and enhances control by a warning signal or contextual stimuli over the avoidance response. Implications for the CS-only response-prevention treatment and the transfer of aversive control are discussed.     

Prior exposure to inescapable electric shock in rats affects extinction behavior after the successful acquisition of an escape response

In Expt 1, rats exposed to 64 inescapable electric shocks in a restrainer or merely restrained were later given either 0, 5, 15 or 30 escape/avoidance training trials with a two-way shuttlebox procedure that does not lead to interference with escape acquisition due to prior exposure to inescapable shock. After escape training all rats were given an escape/avoidance extinction procedure in which shock was inescapable. The rats which had received prior exposure to inescapable shock responded less often and with longer latencies in extinction than did the restrained rats. Experiment 2 demonstrated that this effect is caused by the inescapability of the initial shock treatment. These results were explained in terms of (a) associative interference which minimized the effect of shuttlebox escape training for the preshocked subjects, and (b) a stronger tendency to recognize the presence of an inescapable shock situation during extinction for the preshocked subjects. The relationship between these results and previous work demonstrating that exposure to the escape contingency mitigates the effects of inescapable shock exposure was also discussed.