Partial reinforcement in rat autoshaping with a long CS: Effects of pramipexole and chlordiazepoxide on sign and goal tracking

Separate and combined effects of prenatal and postnatal exposure to ethanol on activity, emotionality, learning, and hippocampal neuroanatomy were examined in infant rats. Neonatal rats from mothers that were fed either a liquid ethanol (E) or control (C) diet on Gestational Days (G) 1-21 were artificially reared during Postnatal Days (P) 4-12 on either 3% ethanol (E) or isocaloric maltose/dextrin (C) in a milk formula. Pups in these treatment groups (EE, EC, CE, and CC) were tested for activity and emotionally in an open field on P19, for acquisition and extinction of an appetitive, straight runaway task on P20-P21, and for the effects of ethanol treatments on alterations in hippocampal neuroanatomy on P21. Differences in activity and emotionally were slight. Ethanol affected both the partial reinforcement acquisition effect and the partial reinforcement extinction effect. Hippocampal cell density (compared with Group CC) showed a 12% reduction in CA1 pyramidal cells and an 11% reduction in mature granule cells in Groups EC and EE; the CA4 area (compared with Group CC) was significantly larger after postnatal exposure (Groups CE and EE). Significant positive correlations were found between rate of extinction after partial reinforcement (PRF) training and CA1 pyramidal cell density in Groups CC and CE. A significant negative correlation was found between extinction rate after PRF training and CA4 area in Group EE.

Conditioned responding extinguishes more slowly after partial (inconsistent) reinforcement than after consistent reinforcement. This Partial Reinforcement Extinction Effect (PREE) is usually attributed to learning about nonreinforcement during the partial schedule. An alternative explanation attributes it to any difference in the rate of reinforcement, arguing that animals can detect the change to nonreinforcement more quickly after a denser schedule than a leaner schedule. Experiments 1a and 1b compared extinction of magazine responding to a conditioned stimulus (CS) reinforced with 1 food pellet per trial and a CS reinforced with 2 pellets per trial. Despite the difference in reinforcement rate, there was no reliable difference in extinction. Both experiments did demonstrate the conventional PREE comparing a partial CS (50% reinforced) with a consistent CS. Experiments 2 and 3 tested whether the PREE depends specifically on learning about nonreinforced trials during partial reinforcement. Rats were trained with 2 CS configurations, A and AX. One was partially reinforced, the other consistently reinforced. When AX was partial and A consistent, responding to AX extinguished more slowly than to A. When AX was consistent and A was partial, there was no difference in their extinction. Therefore, pairing X with partial reinforcement allowed rats to show a PREE to AX that did not generalize to A. Pairing A with partial reinforcement meant that rats showed a PREE to A that generalized to AX. Thus, the PREE depends on learning about nonreinforced trials during partial reinforcement and is not because of any difference in per-trial probability of reinforcement. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Transfer between anticipatory and consummatory tasks involving reward loss

Amphetamine and the multitrial Partial Reinforcement Extinction Effect (PREE) in an operant chamber: Procedural modifications that lead to an attenuation of the PREE

Effects of partial reinforcement on autoshaping in inbred Roman high- and low-avoidance rats

Incentive salience attribution under reward uncertainty: A Pavlovian model

When the conditioned stimulus (CS) is located some distance from the unconditioned stimulus (US), pairings of the CS and US can yield either conditioned approach to the CS (sign tracking) or conditioned approach to the US (goal tracking). However, goal tracking is the more common outcome, and, because of that, goal tracking has come to serve as a “standard” measure of associative learning in several laboratories. In contrast, in previous studies of sexual conditioning with domesticated quail, only sign tracking was observed. In the present study, quail continued to show sign tracking rather than goal tracking whether or not the US was highly localized (Experiment 1), whether food or a sexual US was used (Experiment 2), whether the CS was mobile or immobile (Experiment 3), and whether the CS was 91 or 233 cm from the US compartment (Experiment 4). The present findings encourage caution in the routine use of goal tracking as a measure of learning. The possible mechanisms of goal tracking are discussed in terms of occasion setting and behavior systems theory.

Partial reinforcement schedules, wherein a conditioned stimulus (CS) is intermittently paired with an unconditioned stimulus (US) during associative learning, have been widely studied and found to affect the extinction and recall of learned behaviors. Notably, behaviors conditioned under partial (as opposed to consistent) reinforcement are more resistant to extinction, an effect known as the partial reinforcement extinction effect (PREE). The present study initially aimed to examine the effects of partial reinforcement on the acquisition and recall of fear extinction (FE) when altering the contextual environment. However, our systematic investigation of partial reinforcement using C57BL/6J mice challenges the well-established PREE within the domain of FE learning. Across multiple experimental setups altering CS duration, US intensity, and reinforcement schedules, we consistently found no significant impact of partial reinforcement on the acquisition, consolidation, or recall of FE. Mice exhibited similar patterns of extinction and spontaneous recovery of conditioned fear responses regardless of reinforcement schedule. These findings suggest that partial reinforcement during fear acquisition may not confer resistance to extinction of conditioned freezing, challenging the established understanding of the PREE and prompting a reexamination of how reinforcement schedules affect learning and memory of fear-related behaviors.

Dorsomedial striatum lesions affect adjustment to reward uncertainty, but not to reward devaluation or omission

In rats, the pharmacological (interoceptive) effects of nicotine can serve as a signal (conditional stimulus) in a Pavlovian (classical) conditioning task. In this task, nicotine administration (0.4 mg base/kg, subcutaneous) is typically paired with intermittent access to a liquid sucrose unconditional stimulus; sucrose is withheld on saline sessions. An increase in sucrose receptacle entries (goal tracking) on nicotine sessions indicates conditioning. Given our limited understanding of the functional relationships controlling conditioned responding to a nicotine conditional stimulus, the present research examined nicotine's sensitivity to several manipulations shown to affect the conditioned responding in more widely studied Pavlovian conditioning tasks that use exteroceptive conditional stimuli: number of nicotine conditional stimulus-sucrose unconditional stimulus pairings per session (0, 3, 9, 18, or 36) and the impact of sucrose deliveries in saline sessions. Differential goal tracking developed in fewer sessions and asymptotic conditioned responding magnitude was greater with more nicotine-sucrose pairings. Further, goal tracking was more resistant to extinction (unconditional stimulus withheld) with more conditional-unconditional stimulus pairings during the acquisition phase. The discrimination was not acquired when sucrose presentations (9 or 18) also occurred during saline sessions. Furthermore, expression of the discrimination was disrupted when sucrose was presented in saline sessions; this disruption resulted from goal tracking in saline sessions. These results are consistent with the notion that nicotine-evoked goal tracking results from interoceptive conditioning processes.

Orbitofrontal participation in sign- and goal-tracking conditioned responses: Effects of nicotine

An earlier history of partial or continuous reinforcement produces differential behavioural effects during extinction in the runway, with an earlier partial reinforcement (PRF) leading to an increased resistance to extinction. This effect has been attributed to conditioned frustration or generalization-decrement processes. The actions of antianxiety drugs in this procedure are most easily interpreted as for reducing the emotional or aversive effects of nonreinforcement. In this study, C57Bl/6 mice were trained to asymptotic performance with food reinforcement on 50 or 100% of six trials in daily sessions. The anxiolytic benzodiazepine, chlordiazepoxide (15 mg/kg, intraperitoneally) or saline was administered before subsequent daily extinction sessions. Under saline, earlier PRF produced an increased resistance to extinction. Drug administration increased resistance to extinction, as measured by start, run and goal times, after either continuous or PRF. These findings are consistent with earlier findings of rats, but different from those obtained with chlordiazepoxide during extinction after operant training with either rats or mice. These findings can be interpreted in terms of frustration, anxiety or generalization-decrement theories of PRF.

Five experiments used a magazine approach paradigm with rats to investigate whether learning about nonreinforcement is impaired in the presence of a conditioned stimulus (CS) that had been partially reinforced (PRf). Experiment 1 trained rats with a PRf CS and a continuously reinforced (CRf) CS, then extinguished responding to both CSs presented together as a compound. Probe trials of each CS presented alone revealed that extinction was slower for the PRf CS than the CRf CS, despite being extinguished in compound. In Experiment 2, a CRf light was extinguished in compound with either a CRf CS or a PRf CS that had been matched for overall reinforcement rate. Responding to the light extinguished at the same rate regardless of the reinforcement schedule of the other CS. Experiment 3 replicated this result with a PRf light. Thus, we found no evidence that a PRf CS impairs extinction of another CS presented at the same time. Experiments 4 and 5 extended this approach to study the acquisition of conditioned inhibition by training an inhibitor in compound with either a PRf or CRf excitatory CS. The reinforcement schedule of the excitatory CS had no effect on the acquisition of inhibition. In sum, conditioning with a PRf schedule slows subsequent extinction of that CS but does not affect learning about the nonreinforcement of other stimuli presented at the same time. We conclude that the Partial Reinforcement Extinction Effect is not attributable to a decrease in sensitivity to nonreinforcement following presentation of a PRf CS. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Sign-tracking and goal-tracking are essentially conditioned approach responses which are induced by pairings of conditioned stimulus (CS) and unconditioned stimulus (US). The predictive and incentive motivational properties of CS are important mechanisms of sign-tracking and goal-tracking. The nucleus accumbens, the central nucleus of the amygdala and the anterior cingulate cortex are required for sign-tracking and goal-tracking. But lesions of the cerebral cortex and hippocampus have little effect on sign and goal tracking. Reduced brain dopaminergic function impairs acquisition and expression of sign-tracking. Increased dopamine content in brain can promote goal-tracking. It will be important for future research to standardize categories and settings of CSs and USs, separately or simultaneously measuring sign-tracking and goal-tracking in terms of different research purposes.

Learning under partial reinforcement in the toad ( Bufo arenarum): Effects of lesions in the medial pallium