Effect of interpolated extinction after partial delay of reward training on subsequent reacquisition and extinction

Four groups of albino rats were run four trials a day in a straight runway for 44 days. On the first 15 days, two groups were given continuous immediate reward (IR) and two groups a 50 per cent, schedule of 30-sec. partial delay of reward (PDR). On the next 15 days, one IR group and one PDR group were extinguished, while the other IR and PDR groups remained on their original schedules. In the third phase, all groups received 8 days of training on IR. Finally, all groups were given 6 days of extinction training. In the first extinction, PDR produced greater resistance to extinction than IR. In the second extinction period, the PDR group which had previously been given extinction and the two IR groups extinguished relatively rapidly and at approximately the same rates, while the PDR group which had not been extinguished was significantly more resistant to extinction than the other three groups.     

The effects of post-acquisition-trial sodium amylobarbitone on subsequent extinction behaviour

In a one-trial-per-day runway task, previously trained rats were injected via temporary intravenous cannulae with Sodium Amylobarbitone (SA) 15 mg/kg, or saline, immediately following each of six acquisition trials, according to one of four regimes. The animals were then extinguished with no further drug or saline treatments. Those that had been consistently reinforced (CR) and consistently treated with saline extinguished faster than those that had been partially reinforced (PR) and consistently treated with saline: the brief PR schedule thus generated a typical PR extinction effect. PR animals that had received SA treatments following nonrewarded trials and saline treatments following rewarded trials extinguished faster than those that had received the opposite treatments. Post-nonreward SA treatment during acquisition thus led to a pseudo CR extinction effect, while post-reward SA treatment in acquisition led to an undistorted PR extinction effect. The results are interpreted as showing that there is a critical period occurring between some tens of seconds and a very few minutes after frustrative nonreward which is vulnerable to SA in a non-state-dependent manner, and on which frustrative nonreward's control of subsequent behaviour depends.     

Partial reinforcement and partial delay of reinforcement effects with 72-hour intertrial intervals and interpolated continuous reinforcement

Three groups of rats ran 108 trials in a straight runway, one trial every 3 days. On the first 44 trials, one group received continuous (and immediate) reinforcement (CRF), a second group 50 per cent partial reinforcement (PRF), and the third group a 50 per cent schedule of partial delay of reinforcement (PDR). All groups received CRF on the next 20 trials, and extinction on the last 44 trials. The PRF and PDR groups extinguished at approximately the same rate, and significantly more slowly than the CRF group.     

Evidence of a role for multiple memory systems in behavioral extinction

The acquisition of learned behavior involves multiple memory systems, and hippocampal system damage impairs cognitive learning while leaving stimulus-response habit learning intact. In view of evidence that extinction also involves new learning, the present experiments examined whether multiple memory systems theory may be applicable to the neural bases of extinction. Adult Long-Evans rats were trained to run in a straight-alley maze for food reward. Twenty-four hours later, rats matched for runway latencies during acquisition received extinction training. In a response extinction condition conducive to habit learning, rats performed a runway approach response to an empty food cup. In a latent extinction condition conducive to cognitive learning, rats were placed at an empty food cup without performing a runway approach response. Prior to daily extinction training, neural activity of the dorsal hippocampus was reversibly inactivated via infusion of bupivacaine (0.75%, 0.5 microl/side). Control rats receiving saline infusions displayed extinction behavior in both the response and latent training conditions. In contrast, rats receiving bupivacaine extinguished normally in the response condition, but did not display latent extinction. The findings (1) confirm that learning underlying extinction of the same overt behavior can occur with or without explicit performance of the previously acquired response, (2) indicate that extinction learning produced by response and latent training procedures can be neuroanatomically dissociated, and (3) suggest that similarly to initial task acquisition, the hippocampus may critically mediate extinction in situations requiring the use of cognitive learning, such as when performance of a previously acquired response habit is prevented.     

Extinction of a running response as a function of reinforcement magnitude

Four groups of rats were trained on different sucrose solutions in a straight runway. Terminal running speed was a monotonic function of reinforcement magnitude. After training each group was subdivided, one subgroup being extinguished under spaced, the other under massed conditions. In spaced extinction the animals trained on non extreme reward magnitudes showed most resistance to extinction. It was concluded that resistance to extinction is an inverted U-shaped function of reinforcement magnitude found in training. The massed extinction trials were conducted with a very short inter-trial interval. The animals showed an immediate drop in running speed followed by a gradual recovery and a subsequent decline. The number of trials taken to reach the peak recovery speed was a function of reinforcement magnitude found in training. Results on both massed and spaced extinction trials were interpreted in terms of the facilitatory and inhibitory effects of momentary and conditioned frustration.     

Infantile stimulation and its effects on frustration- and fear-motivated behavior in rats

Infant rats that were either removed from the nest each day (handled) or left undisturbed (nonhandled) were, in adulthood, given 72 food-reinforced runway acquisition trials followed by 24 trials of extinction training with or without shock. Handled and nonhandled control animals were given runway training without food reinforcement. Reinforced rats ran faster than nonreinforced rats, and handled rats ran faster than nonhandled rats during the initial trials of runway acquisition irrespective of the reinforcement condition. Nonhadled rats stopped running sooner than handled rats when shock was introduced in the goalbox, but differences between handled and nonhandled rats given extinction training without shock were small. Results of a second experiment showed no differences between handled and non-handled rats in the magnitude of the depression effect after an incentive shift. It was concluded that infantile handling had little effect on frustration-motivated behavior, but did affect fear-motivated behavior.     

A further study of partial reinforcement in the turtle

Two matched groups of mature painted turtles, Chrysemys picta picta, were trained in a simple runway, one with partial and the other with consistent reinforcement, following which both groups were extinguished. The partially reinforced animals ran more slowly in acquisition, but showed somewhat greater resistance to extinction. The results are compared with those obtained in analogous experiments with other animals.     

Infantile handling and the extinction of responses acquired under food reward

A comparison was made of the runway behaviour of rats which had been handled from Days 1-21 and their non-handled litter mates. The training began on Day 70 after the animals were habituated to a restricted food schedule for 10 days. The subjects were given six trials each day in the runway and were rewarded with a 0.045 g. Noyes pellet. After 10 days of rewarded training trials, subjects were given 6 extinction trials a day for 10 days. Results showed that handled rats ran faster than non-handled rats during acquisition and during the first 3 days of extinction. The extinction data suggested that the relationship between emotionality and effects of frustrative non-reward should be re-evaluated.     

Escape conditioning and goal punishment: Effects of acquisition trials,initial punishment trials,and CS extent

In the first of three experiments in which albino rats were given spaced shockescape trials in a straight runway, groups of 6 animals were given 6 or 24 trials followed by extinction, with or without goal-box punishment. Punishment facilitated behavior after 24 trials but did not significantly affect it after 6. Both punishment and 24 trials led to more “abrupt” extinction. In the second experiment, 6 groups of 6 animals received 6, 12, or 24 trials followed by 54 extinction trials with or without goal punishment on the first 18. All punished groups ran self-punitively, and acquisition trials effects were apparent during and after punishment. In the third experiment, buzzer extent, or duration, was manipulated, and longer extents produced stronger self-punitive effects. The results of all three experiments were interpreted in the context of presumed directive effects of aversive and conditioned aversive stimuli.     

Extinction of a runway response following runway or goal box partial reinforcement

Rats were trained on a consistent reinforcement schedule in a straight runway. They were then switched to one of two partial reinforcement procedures. One group continued to run the full length of the runway, another was placed directly in the goal box. When extinguished in the full length of the runway both groups were more resistant to extinction than groups trained only on consistent reinforcement. An attempt was made to delineate the conditions for a demonstration of the partial reinforcement extinction effect. The results were discussed in relation to frustration theory.     

Determinants of instrumental extinction in terrestrial toads (Bufo arenarum)

Previous research in a water-reinforced instrumental training situation with toads (Bufo arenarum) has shown that performance in both acquisition and extinction is poorer after partial, rather than continuous reinforcement training. In Experiment 1, the performance of a group receiving 24 trials on a 50% partial reinforcement schedule was poorer in acquisition and extinction than that of continuously reinforced groups matched for trials or reinforcements. However, partially reinforced toads extinguished at the same rapid rate as a continuously reinforced group that received training only on the days in which the partial toads received water reinforcement. In Experiment 2, extinction was faster after 10 reinforced acquisition trials than after 30 trials. This evidence suggests that the deleterious effects of partial reinforcement in toads can be explained by a combination of two factors, namely, the distribution of reinforced trials across days and the total number of reinforcements.     

The partial punishment effect following minimal acquisition training: Sodium amobarbital and the stimulus properties of early punished trials

In a runway investigation, six groups of rats received limited runway training such that partial punishment, partial reinforcement, or continuous reinforcement was accompanied by sodium amobarbital or saline. Following an interpolated phase of continuous reinforcement without injections, all groups were given punished extinction. The entire experiment was conducted under widely spaced conditions (ITI = 24 hr). It was found that partial punishment increased resistance to punished extinction relative to partially and continuously reinforced controls when acquisition was given under saline. When partial punishment training was accompanied by amobarbital this effect was eliminated. The drug was observed to have no effect on the punished extinction performance of the partial reinforcement and continuous groups, respectively. Moreover, the partial reinforcement effect (PRE) did not generalize to punished extinction. These data provide information concerning the difference between the stimuli associated with the early trials of punishment and nonreward and indicate that the former but not the latter contain emotional elements.     

Occasional reinforced trials during extinction can slow the rate of rapid reacquisition

Two appetitive conditioning experiments with rats examined reacquisition after conditioned responding was eliminated by either extinction or by a partial reinforcement procedure in which reinforced trials were occasionally presented among many nonreinforced trials. In Experiment 1, reacquisition to a conditional stimulus (CS) that had been conditioned and extinguished was more rapid than acquisition in a group that had received no prior conditioning. However, the addition of occasional reinforced trials to extinction slowed this rapid reacquisition effect. Experiment 2 replicated the result and showed that a procedure in which the CS and the unconditional stimulus (US) were unpaired in extinction interfered even further with reacquisition. The results suggest that rapid reacquisition is ordinarily produced when reinforced trials provide a contextual cue that can renew responding by signaling other acquisition trials (Ricker & Bouton, 1996). The effects of partial reinforcement in extinction are surprising from several theoretical perspectives and have useful clinical implications.     

Different mechanisms of fear extinction dependent on length of time since fear acquisition

Fear extinction is defined as a decline in conditioned fear responses (CRs) following nonreinforced exposure to a feared conditioned stimulus (CS). Behavioral evidence indicates that extinction is a form of inhibitory learning: Extinguished fear responses reappear with the passage of time (spontaneous recovery), a shift of context (renewal), and unsignaled presentations of the unconditioned stimulus (reinstatement). However, there also is evidence to suggest that extinction is an "unlearning" process corresponding to depotentiation of potentiated synapses within the amygdala. Because depotentiation is induced more readily at short intervals following LTP induction and is not inducible at all at a sufficient delay, it may be that extinction initiated shortly following fear acquisition preferentially engages depotentiation/"unlearning," whereas extinction initiated at longer delays recruits a different mechanism. We investigated this possibility through a series of behavioral experiments examining the recoverability of conditioned fear following extinction. Consistent with an inhibitory learning mechanism of extinction, rats extinguished 24-72 h following acquisition exhibited moderate to strong reinstatement, renewal, and spontaneous recovery. In contrast, and consistent with an erasure mechanism, rats extinguished 10 min to 1 h after acquisition exhibited little or no reinstatement, renewal, or spontaneous recovery. These data support a model in which different neural mechanisms are recruited depending on the temporal delay of fear extinction.     

Imitation, social facilitation, and the effects of ACTH 4-10 on rats' bar-pressing behavior

The effects of ACTH 4-10 on rats' imitation learning was examined during the acquisition and extinction of a bar-press response for water reinforcement. Rats were exposed to either a bar-pressing conspecific (OB), an experimentally naive conspecific (ON), or an empty box (OE) during bar-press acquisition. In a factorial design, each rat was then exposed to one of the same three conditions during extinction. An 80 mcg dose of ACTH 4-10 was administered to half of the rats in each group prior to observation. Performance differences during acquisition were generally small, but significant performance differences during extinction were found. Social facilitation was indicated by the finding that rats extinguished in the presence of a conspecific exhibited significantly greater resistance to extinction than rats extinguished in the presence of an empty box. An imitation effect was also found. Rats that observed a bar-pressing conspecific during both acquisition and extinction (group OB-OB) showed significantly greater resistance top extinction than did groups OB-ON, CB-OE, or OE-OE. There were no significant effects of the hormone, however, relative to saline controls.     

Changes Accompanying Practice upon Successive Samples of Verbal Material

Three groups of rats received either continuous, partial, or zero reinforcement in a first acquisition phase which was followed by an extended extinction phase. Then all Ss were given a reacquisition phase under continuous reinforcement conditions followed by a second extinction phase. While the usual partial reinforcement extinction effect (PREE) was found during the major part of the first extinction phase, it disappeared during the last few trials of that phase. No PREE was obtained during the second extinction phase in any of the three sections of the runway. The abolition of the PREE was attributed to the extinction of the r_F-s_F mechanism in the partial reinforcement group.     

Response persistence in the rat following intermittent punishment and partial reward: Effects of trial sequence

Thirty-six rats were given 16 days of partial reward training in a runway. During the final 12 days each of the animals received one foot-shock experience each day. One group received shock on an N trial preceding an R trial (P-R), a second group was shocked on N trials not followed by an R trial (R-P), and the third group received shock after completing all daily trials (Control). Following acquisition the rats were split within each group (one half received 24 trials of unpunished extinction and one half continued to receive partial reward but were punished on every trial). During consistent punishment the P-R animals were more persistent than the R-P or Control rats and during unpunished extinction the P-R and Control animals were equal in persistence but both were superior to the R-P animals. The results were discussed in terms of Capaldi's sequential trial theory.     

Stimulus control of responding in the early trials of differential conditioning

In Experiment 1 two groups of rats were given 12 differential conditioning trials, seven to the rewarded alley (S+) and five to the nonrewarded alley (S?), prior to being extinguished in both alleys. Group S?S+ received S+ trials, following S? trials in acquisition, while Group S+S? did not receive S+ trials following S? trials in acquisition. In extinction S+ and S? trials were presented according to a quasi-random sequence for both groups. Running on the last 3 trials of acquisition was found to be faster following S+ than following S? trials. Group S?S+ showed greater resistance to extinction and less discriminative responding in extinction than Group S+S?. These results suggest that responding in differential conditioning is controlled not merely by S+ and S? but by the memories of reward (S^R) and of nonreward (S^N) as well. When the joint effects of both classes of cues were considered, e.g., S^R+S+, responding in the early trials of differential conditioning was shown to be highly orderly. Experiment 2 was highly similar to Experiment 1 except that Groups S?S+ and S+S? were equated along dimensions not equated in Experiment 1. The results obtained in Experiment 2 were highly similar to those obtained in Experiment 1.     

Dissociations between ABA-, ABC-, and AAB-renewal of Pavlovian modulation in human sequential feature positive discrimination learning

Using a conditioned suppression preparation, we investigated extinction and aba-, abc-, and aab-renewal of Pavlovian modulation in human sequential Feature Positive (FP) discrimination learning, X → A+/A-. Extinction treatment was administered in the acquisition context a (aaa- and aab-groups) or in a new context b (aba- and abc-groups) and comprised X → A- extinction trials. Discriminative X → A/A responding was lost in all groups when tested in the extinction context. In the aba-group, the discriminative X → A/A responding totally recovered when retested in the acquisition context a. For the aaa-, the aab-, and the abc-group, discriminative X → A/A responding did not reappear when tested for renewal in, respectively, contexts a, b, and c. The demonstration of aba-renewal of extinguished modulation, but not abc- and aab-renewal, suggests that extinction in a context different from the acquisition context and a return to the original acquisition context might both be critical for renewal of Pavlovian modulation in human FP-discrimination learning.     

Generalization gradients for acquisition and extinction in human contingency learning

Two experiments investigated the perceptual generalization of acquisition and extinction in human contingency learning. In Experiment 1, the degree of perceptual similarity between the acquisition stimulus and the generalization stimulus was manipulated over five groups. This successfully generated a generalization gradient of acquisition. In the subsequent phase, the response to the generalization stimulus was extinguished in each group. Finally, the acquisition stimulus was presented again. The response recovered differently over groups, thereby establishing the generalization gradient of extinction. In Experiment 2, the acquisition stimulus itself was extinguished before the set of generalization stimuli was tested between groups. One group evidenced a response recovery at test, which suggests that the gradient of acquisition is somewhat broader than the gradient of extinction.