The effect of conditioned inhibition on the specific Pavlovian-instrumental transfer effect

Four experiments examined the effect of Pavlovian conditioned inhibition on specific Pavlovian-instrumental transfer (PIT) in human participants. The task comprised an instrumental phase in which two responses (R1, R2) were each paired with one of two outcomes (O1, O2: R1-->O1, R2-->O2), and a Pavlovian phase, in which two CSs, CS1 and CS2 each signalled one of the two outcomes (CS1-->O1, CS2-->O2). In Experiments 1-2 a conditioned inhibitor, X, predicted the omission of one of the outcomes (e.g. CS1-->O1, CS1X-->nothing). In a subsequent test, performance of R1 and R2 was examined in the presence of CS1 and CS2. A specific PIT effect was observed: R1 was performed more than R2 during CS1, and R2 more than R1 during CS2. This PIT effect was significantly reduced by the presence of the inhibitor X in Experiment 1, in which the Pavlovian phase followed the instrumental phase, and in Experiment 2 in which it preceded it. No such effect was observed when X was presented in the absence of any expectation of the outcomes during the PIT test (Experiment 3a), or when X was trained as a signal for an alternative outcome (Experiment 3b). These results are consistent with the suggestion that the specific PIT effect occurs through a stimulus-outcome-response (S-O-R) mechanism, according to which the CS evokes a representation of the outcome which in turn elicits the response (e.g. CS1-->O1-->R1). The conditioned inhibitor suppresses performance of the response by suppressing activation of the outcome representation

US specificity of occasion setting: hierarchical or configural learning?

Four experiments in rats examined whether occasion setters and target CSs play qualitatively different roles in occasion-setting discriminations. Two visual occasion setters, A and B, signalled reinforcement of two auditory target CSs, x and y, with sucrose and oil (A…x → suc, B…y → oil, A−, B−, x−, y−); in addition two transfer CSs w and z were paired with sucrose and oil (w → suc, z → oil). When w and z were substituted for x and y (A…w, B…w, A…z, B…z) more responding was observed when both stimuli had been paired with the same outcome (Experiments 1 and 3a). No effect was observed when two visual “pseudo-occasion setters”, C and D (paired with sucrose and oil in a trace relation to the US:C… → suc, D… → oil), were substituted for the occasion setters A and B (C…x, D…x, C…y, D…y; Experiments 2, 3b and 4). These results could not be explained in terms of Pavlovian summation: responding to combinations of Pavlovian CSs paired with same or different outcomes was either the same, or lower when both stimuli had been paired with the same outcome (Experiment 4). Implications of these results for theories of occasion setting and configural learning are discussed

Can existing associative principles explain occasion setting? Some old ideas and some new data

Since occasion setting was identified as a type of learning independent of 'simple' associative processes, a great deal of research has explored how occasion setters are established and operate. Initial theories suggested that they exert hierarchical control over a target CS→US association, facilitating the ease with which a CS can activate the US representation and elicit the CR. Later approaches proposed that occasion setting arises from an association between a configural cue, formed from the conjunction of the occasion setter and CS, and the US. The former solution requires the associative principles dictating how stimuli interact to be modified, while the latter does not. The history of this theoretical distinction, and evidence relating to it, will be briefly reviewed and some novel data presented. In summary, although the contribution of configural processes to learning phenomena is not in doubt, configural theories must make many assumptions to accommodate the existing data, and there are certain classes of evidence that they are logically unable to explain. Our contention is therefore that some kind of hierarchical process is required to explain occasion-setting effects

Associative mechanisms involved in specific Pavlovian-to-instrumental transfer (PIT) in human learning tasks

Four experiments compared the effect of forward and backward conditioning procedures on the ability of conditioned stimuli (CSs) to elevate instrumental responding in a Pavlovian-to-instrumental transfer (PIT) task. Two responses were each trained with one distinct outcome (R1->O1, R2->O2), either concurrently (Experiment 1) or separately (Experiments 2, 3 and 4). Then, in Experiments 1 and 2, four CSs were either followed or preceded by one outcome (A->O1, B->O2, O1->C, O2->D). In Experiment 3 each CS was preceded and followed by an outcome: for one group of participants both outcomes were identical (e.g., O1->A->O1, O2->B->O2), but for the other they were different (e.g., O1->A->O2, O2->B->O1). In Experiment 4 two CSs were preceded and followed by identical outcomes, and two CSs by different outcomes. In the PIT tests participants performed R1 and R2 in the presence and absence of the CSs. In Experiments 1 and 2 only the CSs followed by outcomes in Pavlovian training elevated responding. In Experiments 3 and 4 all the CSs elevated responding but based on the outcome that followed them in training. These results support the stimulusoutcome-response (S-O-R) mechanism of specific PIT, according to which CSs elevate responding via activation of its associated outcome representation

Deficits in object-in-place but not relative recency performance in the APPswe/PS1dE9 mouse model of Alzheimer's disease: implications for object recognition

Performance was examined on three variants of the spontaneous object recognition (SOR) task, in 5-month old APPswe/PS1dE9 mice and wild-type littermate controls. A deficit was observed in an object-in-place (OIP) task, in which mice are preexposed to four different objects in specific locations, and then at test two of the objects swap locations (Experiment 2). Typically more exploration is seen of the objects which have switched location, which is taken as evidence of a retrieval-generated priming mechanism. However, no significant transgenic deficit was found in a relative recency (RR) task (Experiment 1), in which mice are exposed to two different objects in two separate sample phases, and then tested with both objects. Typically more exploration of the first presented object is observed, which is taken as evidence of a self-generated priming mechanism. Nor was there any impairment in the simplest variant, the spontaneous object recognition (SOR) task, in which mice are preexposed to one object and then tested with the familiar and a novel object. This was true regardless of whether the sample-test interval was 5 minutes (Experiment 1) or 24 hours (Experiments 1 and 2). It is argued that SOR performance depends on retrieval-generated priming as well as self-generated priming, and our preliminary evidence suggests that the retrieval-generated priming process is especially impaired in these young transgenic animals

Learning about the CS during latent inhibition: preexposure enhances temporal control

In three experiments rats were given nonreinforced preexposure to an auditory stimulus, after which this stimulus and a second, novel cue were paired with food. Lower rates of conditioned responding were observed to the preexposed stimulus across the three experiments, indicative of latent inhibition. The degree to which animals used these cues to time the occurrence of food delivery was also examined. Paradoxically, the response slopes - indicating the rate of increase in responding over the course of the CS - were greater for the preexposed than for the novel cues, consistent with the suggestion that the preexposed stimulus exerted greater temporal control. Moreover, this was the case irrespective of whether the duration of the cue during preexposure differed from that during conditioning. These results suggest that although CS preexposure retards conditioning, it may enhance timing. The findings are discussed in terms of current models of conditioning and timing

Timing impairments in early Alzheimer's disease: Evidence from a mouse model

A key characteristic of Alzheimer's disease (AD) is loss of episodic memory-memory for what happened, where and when; this final aspect-timing-is the focus of the present article. Although timing deficits have been reported in AD patients, few parallel studies have been performed in animals, compromising the translational potential of these findings. We looked for timing impairments in the APPswe/PS1dE9 mouse model of AD at 4-5 months of age, before significant plaques have developed. In Experiments 1 and 2a mice were trained with auditory stimuli that were followed by food, either immediately (delay stimulus; Experiments 1 and 2a) or after a short interval (trace stimulus; Experiment 1). In Experiment 1 APPswe/PS1dEdE9 mice conditioned normally, but showed more variable timing of the delay-conditioned cue. Experiment 2 examined timing of two delay-conditioned CSs, with Experiment 2a using mice 4-5 months old, and Experiment 2b mice at 6-8 months. With the longer conditional stimulus (CS) the transgenic mice showed both more variable timing and earlier timed peak responding than wild-type mice; these effects were not influenced by age. Our results bear similarity to those seen in AD patients, raising the possibility that they have diagnostic potential. They also resemble deficits in animals with dorsal hippocampal lesions, suggesting that they could be mediated by this area. Activated microglia, a component of the immune response thought to be driven by the elevated levels of ?-amyloid, were elevated in both dentate gyrus and striatum of young transgenic mice, providing some support for this proposal. (PsycINFO Database Record (c) 2020 APA, all rights reserved)

Blocking by fixed and variable stimuli: effects of stimulus distribution on blocking

An experiment with rats compared the ability of fixed and variable duration cues to produce blocking. Rats in Group B (Blocking) were trained that both fixed- (F) and variable- (V) duration cues would be followed by food delivery. In a subsequent training stage F and V continued to be reinforced, but F was accompanied by X, and V by Y. In the test phase responding to X and Y was examined. Control Group O (Overshadowing) received identical treatment, except that F and V were nonreinforced in the first training stage. In Group B there was evidence for blocking, but only of X which had been conditioned in compound with the fixed-duration F; there was no evidence for blocking of Y, which had been conditioned in compound with the variable duration V. It is suggested that this result may occur because fixed cues reach a higher, more stable asymptote of associative strength than their variable equivalents

Under the influence of the environment: children’s responding invigorated and biased by predictive cues

Cues that signal motivationally significant consequences can elevate responding and bias choice. A task known as Pavlovian-to-instrumental transfer (PIT) has been used to assess the influence of these cues on independently trained responses, and to study the effect of drug-related and food-related cues on behavior in adult populations, but has not yet been employed in children. This study aimed to develop a simple computer task to study PIT in children. Participants, aged between 7 and 11 years, observed a screen in which different pairings of distinct cartoon images and specific outcomes were presented (images of foods/drinks in Experiment 1, and images of pets in Experiment 2). After this, the participants pressed two keys, each consistently reinforced with one of the two outcomes. Finally, the children pressed both keys in the absence of any outcome, and each cartoon image was presented periodically so that the effect of these cues on behavior could be measured. Experiment 1 showed that the cartoons’ presentations biased responding towards the key that was trained with the same outcome as the cartoon being presented, i.e. outcome- specific PIT. Experiment 2 replicated this finding, and also showed that a cartoon trained with an outcome different than those used to reinforce the responses, elevated performance of both responses, relative to a cartoon that was not paired with any outcome in training, i.e. general PIT. These findings are consistent with those reported in the adult population, and might be a useful tool to study the early development of maladaptive behaviors

When to hold that thought: an experimental study showing reduced inhibition of pre-trained associations in schizophrenia.

Schizophrenia encompasses a wide variety of cognitive dysfunctions, a number of which can be understood as deficits of inhibition. To date, no research has examined ‘conditioned inhibition’ in schizophrenia - the ability of a stimulus that signals the absence of an expected outcome to counteract the conditioned response produced by a signal for that outcome (a conditioned excitor). A computer-based task was used to measure conditioned excitation and inhibition in the same discrimination procedure, in 25 patients with a confirmed diagnosis of schizophrenia and a community-based comparison sample. Conditioned inhibition was measured by a ratio score, which compared the degree to which the inhibitory stimulus and a neutral control stimulus reduced conditioned responding to the excitatory cue: the lower the ratio, the greater the inhibitory learning. At test the ratios were 0.45 and 0.39 for patient and control groups respectively, and the relevant interaction term of the ANOVA confirmed that the degree of inhibition was reduced in the patient group, with an effect size of r = 0.28. These results demonstrate for the first time that inhibitory learning is impaired in schizophrenia. Such an impairment provides an attractive framework for the interpretation of the positive symptoms of schizophrenia. However, we were unable to demonstrate any relationship between the level of conditioned inhibition and medication. Similarly, in the present study it must be emphasised that the available data did not demonstrate any relationship between individual variation in inhibitory learning and the level of positive symptoms as measured by the PANSS. In fact inhibitory learning impairment was relatively greater in participants with a predominantly negative symptom profile and their excitatory learning was also reduced. Accordingly the next step will be to investigate such relationships in a larger sample with a priori defined sub-groups displaying predominantly positive versus predominantly negative symptoms