Dissociation of Pavlovian and instrumental incentive learning under dopamine antagonists.

The administration of the dopamine antagonists, pimozide and α-flupenthixol, to rats reduced Pavlovian–instrumental transfer when a conditioned stimulus (CS) that had been paired with a noncontingent food reward was tested on instrumental performance. The administration of the antagonists during Pavlovian conditioning and/or testing abolished the enhancement of instrumental performance by the CS. The effect of both antagonists on instrumental incentive learning was then examined. After training in which the rats performed 2 responses for different food rewards, they consumed 1 type food under the antagonists and the other type under vehicle during reexposure. When instrumental responding was subsequently tested in extinction, performance was unaffected by whether the rats had been reexposed to the training reward under the antagonists. These results suggest that Pavlovian and instrumental incentive learning are not mediated by a common process. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Choice and contingency in the development of behavioral autonomy during instrumental conditioning.

In two experiments hungry rats received extensive training to lever press for food outcomes before one outcome was devalued by aversion conditioning and responding tested in extinction. If the rats were trained on a concurrent schedule in which two responses yielded different outcomes, performance during the extinction test was reduced by devaluation of the associated outcome. By contrast, if a single response was trained concurrently with the noncontingent presentations of the other outcome, test performance was insensitive to devaluation of the contingent outcome. This finding demonstrates that training on a schedule that offers a choice between responses that yield different outcomes prevents the onset of behavioral autonomy. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dissociations between medial prefrontal cortical subregions in the modulation of learning and action.

The medial prefrontal cortex (mPFC) has been implicated in various attentional functions. This experiment examined the involvement of mPFC subregions in the allocation of attention in learning and action as a function of the predictive accuracy of cues. Rats with dorsal (encompassing anterior cingulate, prelimbic, and infralimbic cortices) or ventral (encompassing mainly infralimbic and dorsopeduncular cortices and tenia tecta) mPFC lesions were trained in a multiple-choice discrimination task in which operant nosepoke responses to some visual cues were consistently (100%) reinforced (CRF) with food, whereas responses to other visual cues were partially (50%) reinforced (PRF). In challenge tests designed to assess attention in the control of action, responding was directed more to CRF cues than to PRF cues in sham and dorsal mPFC-lesioned rats, but ventral mPFC-lesioned rats showed similar levels of responding to both CRF and PRF cues. Nevertheless, when given a choice between simultaneously presented CRF and PRF cues in a cue competition test, all groups responded more to CRF cues. In a subsequent Pavlovian overshadowing phase designed to assess attention in the acquisition of new learning, previously trained CRF cues overshadowed conditioning to novel auditory cues more than did PRF cues in dorsal mPFC-lesioned rats, whereas the opposite pattern was observed in sham and ventral mPFC-lesioned rats. These results suggest a dissociation within the mPFC in the use of reinforcement prediction information to allocate attention for new learning and for the control of action. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Overt attention and predictiveness in human contingency learning.

Two experiments used eye-tracking procedures to investigate the relationship between attention and associative learning in human participants. These experiments found greater overt attention to cues experienced as predictive of the outcomes with which they were paired, than to cues experienced as nonpredictive. Moreover, this attentional bias persisted into a second training phase when all cues were equally predictive of the outcomes with which they were paired, and it was accompanied by a related bias in the rate of learning about these cues. These findings are consistent with the attentional model of associative learning proposed by Mackintosh (1975), but not with that proposed by Pearce and Hall (1980). (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Autoshaping and instrumental learning in the rat.

Conducted 2 experiments to compare the effectiveness of P. L. Brown and H. M. Jenkins's (see record 1968-06958-001) autoshaping procedure with that of instrumental conditioning in the establishment and maintenance of instrumental responding. Ss were 40 male and 32 female Long-Evans rats. In a leverpressing situation, with presentation of the lever signaling trial onset, the 2 procedures were equally effective. When illumination of a key signaled trial onset and the response was pressing the key, the instrumental-training procedure was superior to the autoshaping procedure in establishing and maintaining instrumental responding. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Instrumental and Pavlovian incentive processes have dissociable effects on components of a heterogeneous instrumental chain.

Two experiments compared the effects of Pavlovian stimuli and incentive learning on the performance of a heterogeneous chain of instrumental actions. Using a Pavlovian-instrumental transfer design, the authors found that only a stimulus paired with the same outcome as that earned by performance of the chain produced positive transfer, an effect that was restricted to the action in the chain most proximal to reward delivery. In contrast, after a shift to a nondeprived state, only animals that had previously consumed the instrumental outcome when they were nondeprived decreased instrumental performance. Furthermore, this effect of the incentive learning treatment was limited to performance of the distal action. Together these data suggest that Pavlovian and instrumental incentive manipulations have dissociable effects on instrumental performance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stimulus-outcome interactions during instrumental discrimination learning by rats and humans.

The associative structure mediating goal-directed action was investigated using congruent and incongruent conditional discriminations. The stimulus was the same as the outcome in each component of the congruent discriminations, whereas the stimulus of one component of the incongruent discriminations was the same as the outcome of the other component. Humans, but not rats, learned the congruent discrimination more rapidly than the incongruent discrimination, a difference that the authors attribute to the fact that outcome-response associations caused response conflict in the incongruent discrimination. Moreover, responding was resistant to outcome devaluation following incongruent, but not congruent, training, suggesting that both humans and rats adopted a stimulus-response strategy to resolve the incongruent discrimination. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Endo-N-acetyl-beta-D-glucosaminidases and their potential substrates: structure/function relationships

Endo-N-acetyl-beta-D-glucosaminidases (ENGases) have been defined as the enzymes that hydrolyse the glycosidic bond between an N-acetyl-beta-D-glucosamine residue and the adjacent (partner) monosaccharide within an oligosaccharide chain. Three types of enzymes have been distinguished according to this definition: ENGases acting on murein (type I), those acting on chitin (type II) and, finally, those acting on N-glycans (type III). Considering that N-acetylmuramic acid is a derivative of N-acetylglucosamine (3-O-substituted by a lactyl group), only ENGases acting between two N-acetylglucosamine residues are actually known despite the fact that other possibilities of partner monosaccharides for N-acetyl-beta-D-glucosamine are reported. Similarities in the amino acid sequences were found to occur only between chitin-ENGases and N-glycan-ENGases, but the substrate specificities of these two types of enzymes are different. However, it is possible that certain enzymes are able to cleave more than one type of substrate, and this could in particular explain why the N-glycan-ENGases are largely produced by bacteria in which no potential substrate for this type of enzymes was identified. Further study in this area is expected.     

Stimulus control in instrumental discrimination learning and reinforcement schedule situations.

Investigated ways in which control is exercised over responding by cues associated with reinforcement (RC) as well as nonreinforcement (NC) in discrimination tasks. In Phase 1 of Exp I, with 20 male albino Holtzman rats, either RC or NC was reinforced. In Phase 2, RC and RN were employed as the brighter stimulus (S+) and the less bright stimulus (S–) cues. Results show that differential responding developed less rapidly when the cue reinforced in Phase 1 was the S– rather than the S+ cue in Phase 2, regardless of whether that cue was RC or NC. In Exp II, using 16 male albino Holtzman rats, the S+ cue was a compound of a hedonic cue and a brightness cue, as was the S– cue. Differential responding developed less rapidly when the hedonic cue reinforced in S– was the same as that reinforced in S+, again regardless of whether the cue was RC or NC. Results show that both cues regulated responding and that neither was frustrating to Ss. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Social class and the nature of the incentive in discrimination learning.

"… it… [was] predicted that an interaction exists between social class and the nature of the incentive. Supecifically, it was believed that a nonmaterial incentive is as effective as a material incentive for middle-class Ss, whereas, for lower-class Ss a material incentive is more effective than a nonmaterial one." This belief was tested and results indicate that middle-class "children learn more quickly when given a nonmaterial incentive than when given a material incentive, while the reverse [was] true of lower-class children." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

PIPkins1, their substrates and their products: new functions for old enzymes

The phosphatidylinositolphosphate kinases (PIPkins) are a unique family of enzymes that catalyse the production of phosphorylated inositol lipids. Recent advances have revealed that, due to their ability to utilise a number of different lipid substrates (at least in vitro), this family is potentially able to generate several distinct, physiologically important inositol lipids. Despite their importance, however, our understanding of the regulation of the PIPkins and of their physiological role in cellular signalling and regulation is still poor. Here we describe in turn the diverse physiological functions of the known substrates and major products of the PIPkins. We then examine what is known about the members of the PIPkin family themselves, and their characteristics and regulation.     

Benzodiazepine-induced outcome revaluation and the motivational control of instrumental action in rats

It has been argued that the control of instrumental action by motivational states is indirect, being mediated by the effects these states have on the incentive value of the instrumental outcome (A. Dickinson & B. W. Balleine, 1994). In this study, the benzodiazepine agonist midazolam was found to control instrumental action in a similar manner. Midazolam (1 mg/kg) increased rewarded instrumental performance in rats trained undeprived but only elevated performance in extinction when rats were reexposed to the instrumental outcome under midazolam before the test. This effect of reexposure under midazolam did not transfer to a test conducted under food deprivation, suggesting that it was not produced by drug-induced hunger. Finally, in animals trained hungry, midazolam was found to block outcome devaluation induced by a reduction in food deprivation, indicating that midazolam and food deprivation affect outcome value via a common substrate.     

Evaluative learning with single versus multiple unconditioned stimuli: The role of contingency awareness.

Evaluative conditioning (EC) is obtained when an initially neutral conditioned stimulus (CS) becomes evaluated positively (negatively) after being paired with an evaluatively positive (negative) unconditioned stimulus (US). Most EC studies have paired a given CS with a single US, but EC has also been obtained when a CS was paired with multiple USs of the same valence. This study compares how both variants of CS–US pairing affect awareness for CS–US pairings and ultimately EC effects. EC was assessed directly and indirectly, using evaluative ratings and the Extrinsic Affective Simon Task. Memory for US identity and US valence was assessed to investigate effects of awareness. The multiple-US condition showed attenuated EC effects compared with the single-US condition. The direct measure showed EC effects when awareness of US valence or US identity was present. The indirect measure showed EC effects only when awareness of US identity was present. Results are discussed with regard to the role of contingency awareness in EC. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Associations between the discriminative stimulus and the reinforcer in instrumental learning.

In three experiments we examined whether reinforcement of a response in the presence of a discriminative stimulus (S{d}) resulted in associations between the S{d} and the reinforcer. In Experiments 1 and 2, animals were given food pellets contingent on responding in the presence of one S{d}, and sucrose contingent on responding in the presence of a different S{d}. Next, they were trained to make two new instrumental responses, one reinforced with pellets and one with sucrose. Finally, those responses were tested in the presence of S{d}s. The presence of S{d}-reinforcer associations was inferred from the preferential enhancement of the S{d} of performance of the instrumental response trained with the same reinforcer. In Experiment 3 we compared the transfer obtained with an S{d} and a Pavlovian excitor (CS+). Both stimuli showed preferential transfer on the basis of reinforcer identity, but the level of enhancement was lower for the CS+. These results show that the S{d} provides information about the identity of the reinforcer earned by a response in the normal course of instrumental learning. Several ways in which that knowledge might be encoded are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Magnitude and shift of reward in instrumental aversive learning in rats.

Conducted 3 experiments in which 4 groups of female hooded rats (N = 192) were given 35 classical fear-conditioning trials in 1 side of a 2-compartment box. Ss were then allowed to jump a hurdle to the adjacent box and escape the fear-eliciting stimuli. Reward magnitude (fear reduction) during hurdle jumping for 2 groups was either large or small throughout while for 2 groups it was increased or decreased after some training. Manipulated and nonmanipulated reward varied between experiments. Preshift performance was better with large than with small reward. Positive contrast effects were not found, but a negative contrast effect was obtained in Exp. III. The concepts of incentive motivation and frustration, used to account for performance in appetitively motivated learning tasks, are applied to the findings. (27 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Adolescents exhibit behavioral differences from adults during instrumental learning and extinction.

Adolescence is associated with the development of brain regions linked to cognition and emotion. Such changes are thought to contribute to the behavioral and neuropsychiatric vulnerabilities of this period. We compared adolescent (Postnatal Days 28–42) and adult (Postnatal Day 60+) rats as they performed a simple instrumental task and extinction. Rats were trained to poke into a hole for a food-pellet reinforcer. After six days of training, rats underwent extinction sessions in which the previously rewarded behavior was no longer reinforced. During extinction, we examined the effects of continued presentation of a cue light and food restriction. Adults and adolescents exhibited similar performance during training, although adolescents made more task-irrelevant pokes, consistent with increased exploration. Adults made more premature pokes, which could indicate a more exclusive focus on the task. During extinction, adolescents made more perseverative (previously reinforced) pokes than adults. This behavior was strongly modulated by the combination of motivational factors present (food restriction and cue light), indicating that adolescents were differentially sensitive to them. Furthermore, food restriction induced greater open-field activity in adolescents but not in adults. Thus, as the neural circuitry of motivated behavior develops substantially during adolescence, so too does the behavioral sensitivity to motivational factors. Understanding how such factors differently affect adolescents may shed light on mechanisms that lead to the development of disorders that are manifested during this period. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Random motor generation in a finger tapping task: influence of spatial contingency and of cortical and subcortical hemispheric brain lesions

OBJECTIVE: To test the hypothesis that, during random motor generation, the spatial contingencies inherent to the task would induce additional preferences in normal subjects, shifting their performances farther from randomness. By contrast, perceptual or executive dysfunction could alter these task related biases in patients with brain damage. METHODS: Two groups of patients, with right and left focal brain lesions, as well as 25 right handed subjects matched for age and handedness were asked to execute a random choice motor task--namely, to generate a random series of 180 button presses from a set of 10 keys placed vertically in front of them. RESULTS: In the control group, as in the left brain lesion group, motor generation was subject to deviations from theoretical expected randomness, similar to those when numbers are generated mentally, as immediate repetitions (successive presses on the same key) are avoided. However, the distribution of button presses was also contingent on the topographic disposition of the keys: the central keys were chosen more often than those placed at extreme positions. Small distances were favoured, particularly with the left hand. These patterns were influenced by implicit strategies and task related contingencies. By contrast, right brain lesion patients with frontal involvement tended to show a more square distribution of key presses--that is, the number of key presses tended to be more equally distributed. The strategies were also altered by brain lesions: the number of immediate repetitions was more frequent when the lesion involved the right frontal areas yielding a random generation nearer to expected theoretical randomness. The frequency of adjacent key presses was increased by right anterior and left posterior cortical as well as by right subcortical lesions, but decreased by left subcortical lesions. CONCLUSIONS: Depending on the side of the lesion and the degree of cortical-subcortical involvement, the deficits take on a different aspect and direct repetions and adjacent key presses have different patterns of alterations. Motor random generation is therefore a complex task which seems to necessitate the participation of numerous cerebral structures, among which those situated in the right frontal, left posterior, and subcortical regions have a predominant role.     

Effects of concurrent load on feature- and rule-based generalization in human contingency learning.

The effect of concurrent load on generalization performance in human contingency learning was examined in 2 experiments that employed the combined positive and negative patterning procedure of Shanks and Darby (1998). In Experiment 1, we tested 32 undergraduates and found that participants who were trained and tested under full attention showed generalization consistent with the application of an opposites rule (i.e., single cues signal the opposite outcome to their compound), whereas participants trained and tested under a concurrent cognitive load showed generalization consistent with surface similarity. In Experiment 2, we replicated the effect with 148 undergraduates and provided evidence that it was the presence of concurrent load during training, rather than during testing, that was critical. Implications for associative, inferential, and dual-process accounts of human learning are discussed. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Disciplinary encounters between young boys and their mothers and fathers: Is there a contingency system?

In a study with 46 sets of male twins and 44 male singletons (mean age 32.4 mo), parents' actions preceding verbal control, considered in addition to their verbal control, were analyzed as 2nd-order antecedents of child compliance. When added to a simple command, physical control detracts from the effectiveness of the command to procure compliance, but positively toned action increases it. Analysis of parents' responses to children's compliance or noncompliance revealed that they were both most often followed by parental nonresponse. The mother tended to react more often to compliance than the father did. The father's presence affected the mother–child interactions beneficially, but she was the major disciplinarian. The kind of response made by parents was generally more a function of the overall base rate of the different parental action categories than a response determined contingently by the child's act. In natural encounters, the control system seems somewhat erratic. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Conjunctive representations in learning and memory: Principles of cortical and hippocampal function.

The authors present a theoretical framework for understanding the roles of the hippocampus and neocortex in learning and memory. This framework incorporates a theme found in many theories of hippocampal function: that the hippocampus is responsible for developing conjunctive representations binding together stimulus elements into a unitary representation that can later be recalled from partial input cues. This idea is contradicted by the fact that hippocampally lesioned rats can learn nonlinear discrimination problems that require conjunctive representations. The authors' framework accommodates this finding by establishing a principled division of labor, where the cortex is responsible for slow learning that integrates over multiple experiences to extract generalities whereas the hippocampus performs rapid learning of the arbitrary contents of individual experiences. This framework suggests that tasks involving rapid, incidental conjunctive learning are better tests of hippocampal function. The authors implement this framework in a computational neural network model and show that it can account for a wide range of data in animal learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)