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Three experiments examined whether second-order conditioning resulted in the formation of a fully-featured temporal map, as proposed by the temporal coding hypothesis. Experiments 1 and 2 examined second-order conditioning with different first- and second-order relationships. Measures of the strength of second-order conditioning were mostly consistent with the temporal coding hypothesis; second-order conditioning was best with arrangements in which CS2 occurred prior to the time that the US normally occurred during CS1-US presentations. However, there was no evidence of anticipatory timing during CS2 during second-order conditioning. A third experiment directly examined whether a fully-featured temporal map was formed during second-order conditioning by examining the acquisition of anticipatory timing in subsequent reinforced second-order trials. The results of Experiment 3 suggested that the effects obtained in Experiments 1 and 2 were due to learning of the temporal order and coincidence of events that resulted in the formation of an ordinal temporal map, but that precise durations were not encoded.

A Pavlovian appetitive conditioning preparation with rats was used to assess the effect of an extinction cue on reinstatement after extinction. Reinstatement provides an animal analog to relapses following treatment in humans; it occurs when a conditioned stimulus elicits strong conditioned responding following extinction and presentation of the unconditioned stimulus. An extinction cue is a stimulus presented during extinction of behavior controlled by the conditioned stimulus and is also presented later when the behavior would be expected to return/relapse following extinction (i.e., when reinstatement occurs). An extinction cue has been shown previously to reduce and prevent other instances of relapse analogs (spontaneous recovery and renewal). The authors tested whether an extinction cue would also reduce reinstatement, and included controls for reinstatement and for potential alternative accounts of an extinction cue’s effect on reinstatement. The extinction cue reduced reinstatement, but a cue not presented during extinction did not affect reinstatement, bearing on several alternative explanations of the reduction effect. The authors suggest the extinction cue reduces reinstatement by helping to retrieve a memory encoded during extinction, and that reinstatement is due at least in part to a failure to retrieve that extinction memory.

Highlights • Attention and stimulus selection deficits in Gdi1-null Intellectual Disability model. • Behavioral deficits correlated with fronto-striatal system dysfunction. • A major role for glutamatergic activity in fronto-striatal circuitry dysfunction. • Correlation between reported patient’s cognitive deficits and present findings., RAB-GDP dissociation inhibitor 1 (GDI1) loss-of-function mutations are responsible for a form of non-specific X-linked Intellectual Disability (XLID) where the only clinical feature is cognitive impairment. GDI1 patients are impaired in specific aspects of executive functions and conditioned response, which are controlled by fronto-striatal circuitries. Previous molecular and behavioral characterization of the Gdi1-null mouse revealed alterations in the total number/distribution of hippocampal and cortical synaptic vesicles as well as hippocampal short-term synaptic plasticity, and memory deficits. In this study, we employed cognitive protocols with high translational validity to human condition that target the functionality of cortico-striatal circuitry such as attention and stimulus selection ability with progressive degree of complexity. We previously showed that Gdi1-null mice are impaired in some hippocampus-dependent forms of associative learning assessed by aversive procedures. Here, using appetitive-conditioning procedures we further investigated associative learning deficits sustained by the fronto-striatal system. We report that Gdi1-null mice are impaired in attention and associative learning processes, which are a key part of the cognitive impairment observed in XLID patients.

SUMMARYIn order to successfully forage in an environment filled with rewards and threats, animals need to rely on familiar structures of their environment that signal food availability. The central amygdala (CeA) is known to mediate a panoply of consummatory and defensive behaviors, yet how specific activity patterns within CeA subpopulations guide optimal choices is incompletely understood. In a paradigm of appetitive conditioning in which mice freely forage for food across a continuum of cues, we find that two major subpopulations of CeA neurons, Somatostatin-positive (CeASst) and protein kinase Cδ-positive (CeAPKCδ) neurons can assign motivational properties to environmental cues and encode memory of goal location. While the proportion of food responsive cells was higher within CeASst than CeAPKCδ neurons, only the activities of CeAPKCδ, but not CeASst, neurons were required for learning of contextual food cues. Since CeAPKCδ neurons are known to promote a range of defensive behaviors, our findings point to a model in which CeA circuit components are not organized in specialized functional units but can process both aversive and rewarding information in a context and experience dependent manner.HIGHLIGHTSTwo populations of central amygdala (CeA) neurons, CeAPKCδ and CeASst neurons can assign motivational properties to environmental cues and encode memory of goal location.The proportion of food responsive cells was higher among CeASst, than CeAPKCδ neurons.The activities of CeAPKCδ, but not CeASst, neurons are required for learning of contextual food cues. CeAPKCδ neurons represent a “general encoding” population selecting defensive and appetitive responses depending on context.

Two Pavlovian appetitive conditioning experiments with rats demonstrated that spontaneous recovery can be strongly reduced (prevented). The experiments also investigated potential common factors associated with that prevention of spontaneous recovery after extinction. After pairings of a conditioned stimulus (CS) with a food unconditioned stimulus (US), an extinction cue (EC) was presented during extinction and spontaneous recovery testing with the CS. Replicating Brooks and Bowker (2001), EC–US pairings in the CS extinction–test interval subsequently resulted in the EC strongly reducing (preventing) spontaneous recovery to the CS (Experiment 1). Experiment 1 also assessed an “erasure” hypothesis of how the EC may reduce spontaneous recovery. Experiment 2 assessed EC– or US–alone presentations, or unpairings of EC and US, in the CS extinction–test interval. Spontaneous recovery was also prevented when the EC was presented alone or unpaired with the US, but USs alone interfered with the EC’s spontaneous recovery–preventing effect. No evidence was found for the EC operating by erasure, conditioned inhibition, generalized extinction, or generalized extinction. Together the results suggest that after CS extinction additional EC presentations are sufficient to prevent spontaneous recovery.

Two Pavlovian appetitive conditioning experiments with rats assessed extinction cue (EC) transfer using spontaneous recovery tests. In each experiment, after conditioned stimulus (CS) A-US pairings, an EC (X) was presented during A-extinction, followed by spontaneous recovery testing with A. Experiment 1 tested for transfer between ECs; the additional CS (B) was conditioned and then was extinguished with a second EC (Y). CS A was tested with X and with Y (the possible transfer EC). Experiment 2 tested for transfer between an EC and an explicitly trained serial negative occasion setter (OS). Prior to testing with A, Y was trained in a serial Y→C-, C + discrimination; a Z→B-, B + discrimination was also trained. A was tested with X and with Y (with Y as the possible transfer OS). X and Y were also tested with B (where X with B tests possible EC-OS transfer). In each experiment Y did not reduce spontaneous recovery to A, showing no transfer of one EC to another (Experiment 1) and no transfer of a serial negative OS to a CS (A) extinguished with an EC (X; Experiment 2). X did not reduce responding to B, showing no transfer of an EC to the target CS of a serial negative OS discrimination, although Y did transfer to B (Experiment 2) showing transfer between serial OSs. X did reduce responding to the CS (A) it had occurred with during extinction (Experiments 1 and 2). The results are discussed in terms of EC characteristics and regarding theories of an EC's possible mechanisms.

Although eating desires can be easily learned, their extinction appears more difficult. The present two-session study aimed to investigate the role of eating expectancies in the short and longer-term extinction of eating desires. In addition, the relationship between eating desires and conditioned evaluations was examined to test whether they might share a similar mechanism. It was hypothesized that the short-term extinction of eating desires would be more successful after the disconfirmation of eating expectancies (instructed extinction or IE), while resulting in worse longer-term extinction because omission of the food reward during extinction is not surprising. In contrast to the hypotheses, it was found that IE had no effect on the short-term and longer-term extinction of eating desires. Eating desires correlated with conditioned evaluations only to some extent. It is concluded that eating expectancies do not mediate the short-term extinction of conditioned eating desires. In addition, their longer-term extinction does not appear to be facilitated by a greater violation of eating expectancies. This suggests that it might not be necessary to focus on expectancy violation in cue exposure therapy to reduce eating desires.

Background and objectives Successful long-term dieting appears to be difficult, and part of its difficulty might be explained by processes related to classical appetitive conditioning. Increasing the speed of extinction of appetitive responses to food cues and decreasing the magnitude of returns of these responses could help increase the long-term effectiveness of weight loss attempts. Two extinction techniques hypothesized to slow down rapid reacquisition of conditioned appetitive responses were investigated: the provision of 1) occasional reinforced extinction trials (OR) and 2) unpaired unconditioned stimuli (USs) during extinction (UNP). Methods After acquisition, participants (N = 90) received one of three extinction trainings: OR, UNP, or normal extinction (control), followed by a reacquisition phase. Their desire to eat, US expectancy, and salivation were measured. Effects of impulsivity on different phases of appetitive conditioning were also assessed. Results It was found that both extinction techniques were successful in reducing the rate of reacquisition of US expectancies. Participants in the OR condition also demonstrated a slower extinction of US expectancies and desires to eat. However, the reacquisition of conditioned desires was not affected by either extinction technique. Impulsivity did not moderate responses during acquisition or extinction, but appeared to slow down the reacquisition of conditioned desires. Limitations US expectancies and eating desires were not completely extinguished, and a few differences in baseline responses caused difficulty in interpreting some of the findings. Conclusions It is concluded that the provision of occasional reinforced extinction trials and unpaired USs seem promising techniques to slow down reacquisition, but that additional studies are needed.

Objective: Emotional eating has been suggested to be a learned behaviour; more specifically, classical conditioning processes might be involved in its development. In the present study we investigated whether a negative mood facilitates appetitive conditioning and whether trait impulsivity influences this process. Method: After undergoing either a negative or neutral mood induction, participants were subjected to a differential classical conditioning procedure, using neutral stimuli and appetizing food. Two initially neutral distinctive vases with flowers were (CS+) or were not (CS-) paired with chocolate mousse intake. We measured participants' expectancy and desire to eat (4 CS+ and 4 CS- trials), salivation response, and actual food intake. The BIS-11 was administered to assess trait impulsivity. Results: In both mood conditions, participants showed a classically conditioned appetite. Unexpectedly, there was no evidence of facilitated appetitive learning in a negative mood with regard to expectancy, desire, salivation, or intake. However, immediately before the taste test, participants in the negative mood condition reported a stronger desire to eat in the CS+ compared to the CS- condition, while no such effect occurred in the neutral group. An effect of impulsivity was found with regard to food intake in the neutral mood condition: high-impulsive participants consumed less food when presented with the CS+ compared to the CS-, and also less than low-impulsive participants. Discussion: An alternative pathway to appetitive conditioning with regard to emotions is that it is not the neutral stimuli, but the emotions themselves that become conditioned stimuli and elicit appetitive responses. (C) 2015 Elsevier Ltd. All rights reserved.

Although post-traumatic stress disorder (PTSD) and addiction are very different disorders, both are characterized by hyperreactivity to trauma- or drug-related cues, respectively. We investigated whether an appetitive conditioning task, Pavlovian conditioned approach, which predicts vulnerability to reinstatement of cocaine-seeking, also predicts fear incubation, which may be a marker for vulnerability to PTSD. We classified rats based on whether they learned to approach and interact with a food predictive cue (sign-trackers), or, whether upon cue presentation they went to the location of impending food delivery (goal-trackers). Rats were then exposed to extensive Pavlovian tone-shock pairings, which causes the fear response to increase or “incubate” over time. We found that the fear incubation effect was only present in sign-trackers. The behavior of goal-trackers was more consistent with a normal fear response – it was most robust immediately after training and decayed slowly over time. Sign-trackers also had lower levels of brain-derived neurotrophic factor (BDNF) protein in the prefrontal cortex than goal-trackers. These results indicate that, while many factors likely contribute to the disproportionate co-occurrence of PTSD and substance abuse, one such factor may be a core psychological trait that biases some individuals to attribute excessive motivational significance to predictive cues, regardless of the emotional valence of those cues. High levels of BDNF in the prefrontal cortex may be protective against developing excessive emotional and motivational responses to salient cues.

The majority of experiments exploring context-dependent extinction learning employ Pavlovian fear conditioning in rodents. Since mechanisms of appetitive and aversive learning are known to differ at the neuronal level, we sought to investigate extinction learning in an appetitive setting. Working with pigeons, we established a within-subject ABA renewal paradigm based on Rescorla (Q J Exp Psychol 61:1793) and combined it with pharmacological interventions during extinction. From the fear conditioning literature, it is known that both prefrontal cortex and the hippocampus are core structures for context-specific extinction learning. Accordingly, we transiently inactivated the nidopallium caudolaterale (NCL, a functional analogue of mammalian prefrontal cortex) and the hippocampus in separate experiments by intracranial infusion of the sodium-channel blocker tetrodotoxin immediately before extinction training. We find that TTX in both structures non-specifically suppresses conditioned responding, as revealed by a reduction of response rate to both the extinguished conditioned stimulus and a control stimulus which remained reinforced throughout the experiment. Furthermore, TTX during extinction training impaired later extinction retrieval assessed under drug-free conditions. This was true when responding to the extinguished stimulus was assessed in the context of extinction but not when tested in the context of acquisition, although both contexts were matched with respect to their history of conditioning. These results indicate that both NCL and hippocampus are involved in extinction learning under appetitive conditions or, more specifically, in the consolidation of extinction memory, and that their contribution to extinction is context-specific.

Summary Accurately predicting an outcome requires that animals learn supporting and conflicting evidence from sequential experience. In mammals and invertebrates, learned fear responses can be suppressed by experiencing predictive cues without punishment, a process called memory extinction. Here, we show that extinction of aversive memories in Drosophila requires specific dopaminergic neurons, which indicate that omission of punishment is remembered as a positive experience. Functional imaging revealed co-existence of intracellular calcium traces in different places in the mushroom body output neuron network for both the original aversive memory and a new appetitive extinction memory. Light and ultrastructural anatomy are consistent with parallel competing memories being combined within mushroom body output neurons that direct avoidance. Indeed, extinction-evoked plasticity in a pair of these neurons neutralizes the potentiated odor response imposed in the network by aversive learning. Therefore, flies track the accuracy of learned expectations by accumulating and integrating memories of conflicting events., Graphical Abstract, Highlights • Omission of expected punishment extinguishes learned avoidance behavior • Lack of punishment is learned as a positive experience • The original aversive and the new appetitive memory co-exist in different places • Opposing memories are integrated within specific output neurons to steer behavior, The omission of punishment is remembered as a rewarding experience, and this positive memory then competes against prior aversive memory to mediate the extinction of avoidance behavior.

Appetitive conditioning is considered a central mechanism for the vulnerability to psychiatric disorders. However, the investigation of individual differences that are related to altered appetitive learning has been almost neglected so far. The aim of this study was to investigate the link between neuroticism and appetitive conditioning processes. 79 subjects participated in a differential conditioning procedure in which a conditioned stimulus (CS+) was paired with a reward (money) after a fast behavioral response, while a second conditioned stimulus (CS−) was never followed by a reward, irrespective of the behavioral response. As a main result, neuroticism correlated negatively with the underlying neural processes of appetitive conditioning in females, but not in males. In detail, higher levels of neuroticism were associated with decreased neural responses in the left (p = .001) and right amygdala (p = .011), left (p = .063) and right (p = .019) nucleus accumbens, and left (p = .002) and right (p = .021) orbitofrontal cortex (all results are family-wise-error-corrected). The present results support previous findings, which also showed an inverse sex-specific effect in the context of neuroticism and emotional processing in females. In addition, the findings suggest that neuroticism is not solely linked to increased amygdala sensitivity during the processing of negative stimuli but also to decreased neural responses when processing rewarding stimuli. Possible explanations for the sex differences and implications are discussed.

An extinction cue (EC) is a discrete stimulus that is presented during Pavlovian extinction, contingent and with close contiguity to the conditioned stimulus (CS) under extinction treatment. When this EC is presented during a recovery test (e.g., renewal, spontaneous recovery), it typically prevents response recovery. At least two associative mechanisms have been proposed to explain this effect: an EC might become a conditioned inhibitor, or it might become a negative occasion setter. Three experiments, using rats as subjects, assessed whether an EC prevented renewal, and evaluated with summation and retardation tests as to whether it acquired conditioned inhibition. Experiment 1 was conducted in a fear conditioning preparation, and experiments 2 and 3 in an appetitive conditioning paradigm. The results of the three experiments showed that an EC did not attenuate renewal compared to a novel cue, and subsequent inhibition tests also showed no difference between the EC and a novel stimulus. These results suggest that the effect might be more difficult to detect than expected, and are discussed within the framework of previous studies.

Animals can learn that specific contexts are associated with important biological events such as food intake through classical conditioning. Very few studies suggest this is also possible in humans and contextual appetitive conditioning might even be a main determinant of habitual overeating in vulnerable humans. A Virtual Reality laboratory was used to test whether humans show conditioned responding (increased food desires and expectations, increased salivation and increased food intake) to a specific context after repeated pairings of this context with intake. It was also examined whether the personality trait impulsivity strengthens this contextual appetitive conditioning. Conditioned context-induced reactivity was indeed demonstrated and impulsivity predicted increased intake in only the intake-associated context. It is concluded that humans easily learn desires to eat in intake-related environments. The data also suggest that in particular more impulsive people are vulnerable for conditioned context-induced overeating. This relatively easy learning of associations between specific contexts and intake might stimulate habitual overeating and contribute to increased obesity prevalence.

SummaryIt is broadly accepted that long-term memory (LTM) is formed sequentially after learning and short-term memory (STM) formation, but the nature of the relationship between early and late memory traces remains heavily debated [1–5]. To shed light on this issue, we used an olfactory appetitive conditioning in Drosophila, wherein starved flies learned to associate an odor with the presence of sugar [6]. We took advantage of the fact that both STM and LTM are generated after a unique conditioning cycle [7, 8] to demonstrate that appetitive LTM is able to form independently of STM. More specifically, we show that (1) STM retrieval involves output from γ neurons of the mushroom body (MB), i.e., the olfactory memory center [9, 10], whereas LTM retrieval involves output from αβ MB neurons; (2) STM information is not transferred from γ neurons to αβ neurons for LTM formation; and (3) the adenylyl cyclase RUT, which is thought to operate as a coincidence detector between the olfactory stimulus and the sugar stimulus [11–14], is required independently in γ neurons to form appetitive STM and in αβ neurons to form LTM. Taken together, these results demonstrate that appetitive short- and long-term memories are formed and processed in parallel.

Ethanol's motivational consequences have been related to the actions of acetaldehyde, a metabolic product of ethanol oxidation. The present study assessed the role of acetaldehyde in the motivational effects of ethanol on pre-weanling rats. In Experiment 1 pups (postnatal days 13–14, PD 13–14) were given systemic administration of d-penicillamine (DP, a drug that sequesters acetaldehyde: 0, 25, 50 or 75 mg/kg) before pairings of 1.0 g/kg ethanol and a rough surface (sandpaper, conditioned stimulus, CS). At test, pups given sandpaper-ethanol pairings exhibited greater preference for the CS than unpaired controls, but this preference was not expressed by pups given DP. Pre-training administration of 25 or 50 mg/kg DP completely blocked the expression of ethanol-mediated appetitive conditioning. D-penicillamine did not alter blood ethanol levels. Subsequent experiments revealed that ethanol-induced activation was blocked by central (intra-cisterna magna injections, volume: 1 μl, dose: 0 or 75 μg) but not systemic treatment with DP (0, 25, 50 or 75 mg/kg; ip). These results indicate that: (a) pre-weanling rats are sensitive to the reinforcing effect of ethanol, and (b) that this effect is associated with the motor activating effect of the drug. These effects seem to be mediated by the first metabolite of ethanol, acetaldehyde.

d-Cycloserine, a partial NMDA agonist, significantly accelerated extinction of a cocaine-induced conditioned place preference (CPP) when rats were given systemic injections immediately, but not 4h, after each extinction trial. Infusions directly into the basolateral amygdala had a similar effect. The facilitative effect of d-cycloserine on the extinction of appetitive conditioning is consistent with the idea of the formation of new learned associations during extinction.

Although environmental enrichment is presumed to enhance learning, appetitive behavior may also be altered by this experience: anticipatory responding for sucrose is reduced in environmentally enriched (EE) rats [van der Harst, J.E., Baars, A.M. and Spruijt, B.M. Standard housed rats are more sensitive to rewards than enriched housed rats as reflected by their anticipatory behaviour. Behav Brain Res 2003;142:151-156]. To assess the impact of differential environmental experience on learning and appetitive behavior, we trained 17 EE and socially isolated (SI) rats in a three-phase, operant-shaping procedure for sucrose reinforcement. In phase one, a feeder cue was paired with sucrose availability. In phase two, a nose poke to either one of two lit holes on the opposing wall activated the feeder cue. In phase three, the feeder cue was elicited by a poke to a single lit hole. While acquisition rates in phase one and phase two were similar, EE animals reached phase-three criteria [completion of 100 trials in 45 min and 15 or fewer bad pokes] faster than SI animals. These two groups showed similar session completion rates, reinforced and non-reinforced licking responses, and overall behavioral activity during phase three acquisition; however, SI rats performed more bad pokes (responses to the non-lit hole after nose-poke cue onset) and intertrial interval (ITI) pokes during this training period. Because all ITI (and presumably many bad) pokes were initiated before onset of nose-poke cue, this difference indicates greater anticipatory responding in SI animals. This experience-dependent alteration in appetitive behavior may explain, in part, the tendency of SI rats to show attenuated learning rates in appetitive contexts in which complex contingencies exist.

The amygdala is a heterogeneous structure that has been implicated in a wide variety of functions, most notably in fear conditioning. From this research, an influential serial model of amygdala processes has emerged in which aversive learning is mediated by the amygdala basolateral nucleus whereas performance, in this case of various defensive reflexes, is mediated by the central nucleus. By contrast, recent evidence from appetitive conditioning studies suggests that the basolateral and central nuclei operate in parallel to mediate distinct incentive processes: the basolateral nucleus encodes emotional events with reference to their particular sensory-specific features, whereas the central nucleus encodes their more general motivational or affective significance. Given that there is little if any direct behavioral evidence for the serial model, we suggest that more attention should be given to the claims of the parallel view.

Four experiments with rats investigated whether the time between appetitive conditioning trials can serve as a discriminative cue for responding during the next conditional stimulus (CS). In Experiment 1, rats that received extinction trials with a 4-min intertrial interval (ITI) showed spontaneous recovery after a retention interval of 16 min, whereas rats that received extinction with a 16-min ITI did not. Experiments 2 and 3 investigated more explicit discriminations between the 4- and 16-min ITIs. When a 16-min ITI signaled that the CS would be reinforced and a 4-min ITI signaled that it would not, the ITIs modulated responding to the CS. But when the 4-min ITI signaled reinforcement and the 16-min ITI did not, there was less evidence of modulation by the ITIs. This asymmetry was due at least partly to a difficulty in performance rather than learning. Experiment 4 investigated similar discriminations with 1- and 4-min ITIs. Here the results took a different form: time in the reinforced ITI elicited responding directly, but did not modulate responding to the CS. ITI can function as a contextual cue, and the results suggest new similarities between the processes behind interval timing and associative learning.

Three experiments examined absolute (Experiment 1) and relative (Experiments 2a and 2b) duration effects on blocking. In Experiment 1, rats were pretrained with a short or long conditioned stimulus (CS1) followed by food, after which they were given reinforced short-short or long-long CS1-CS2 simultaneous compounds. Compared to overshadowing control groups, both pretrained groups displayed blocking, and there was no clear effect of absolute stimulus duration on the magnitude of blocking. In Experiments 2a and 2b, the rats received partially overlapping short-long CS1-CS2 compounds. In both experiments, a long CS1 blocked a short CS2, but not vice versa. This was the case when the long CS1 was nine times (Experiment 2a) or only 1.5 times (Experiment 2b) the duration of the short CS2. The pattern of results is most consistent with a real-time model of conditioning, such as the Sutton and Barto [Sutton, R.S., Barto, A.G., 1990. Time derivative models of Pavlovian reinforcement. In: Gabriel, M.R., Moore, J.W. (Eds.), Learning and Computational Neuroscience: Foundations of Adaptive Networks. MIT Press, Cambridge, MA, 497-537] temporal difference model.

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.

Two experiments examined the susceptibility of excitation and inhibition to contextual change when the conditioned stimulus (CS) was ambiguous using an appetitive conditioning paradigm. In Experiment 1, excitation to a CS was lost with a context switch when inhibition had been learned to the CS in a prior feature-negative (FN) discrimination. Control groups that had received either more or less excitatory conditioning in the absence of inhibitory pretraining showed no loss. In Experiment 2 inhibition was lost with a context switch in a group that had received excitatory and then inhibitory conditioning with the CS. No loss was observed in a group that had not received excitatory pretraining. The results suggest that contexts are especially likely to control performance to ambiguous CSs when they can modulate the second of two learned associations. Results are discussed in terms of their implications for occasion setting and modern conditioning theory.

Two appetitive conditioning experiments with rats investigated whether the degree of generalization between a compound and its component parts is fixed or variable. Both experiments used a two-stage transfer design. In Stage 1, the elemental groups learned that a compound and its component parts signaled the same outcome (i.e. C+, D+, CD+), whereas the configural groups learned that a compound and its component parts signaled different outcomes (i.e. C+, D+, CD−, where ‘+’ is pellets and ‘−’ is no pellets). In Stage 2, the rats were tested for reductions in generalization. Experiment 1 found no evidence that past configural learning reduced generalization when a new set of alike-treated A and B elements were presented in compound for the first time. Experiment 2 found no evidence that past configural learning reduced generalization when the stimuli of Stage 1 were presented in a new C−, D−, CD+ relation. In contrast to findings with humans, these results suggest that past experience plays a minor role in how stimuli are encoded in animal conditioning.

Item does not contain fulltext Three experiments examined spontaneous recovery from extinction of appetitive conditioned responding (CR) as a function of training history. Rats first received reinforced and non-reinforced conditioning trials. Groups of rats were equated for total number of reinforced trials but differed in the number of non-reinforced trials, or in the order of reinforced and non-reinforced trials. CR was then extinguished in all groups. Subsequently, the extent of recovery of CR was assessed in a test session performed either 1 or 17 days after the last extinction session. After a 17-day delay, rats that had received all reinforced trials immediately prior to the first extinction session showed stronger recovery than did rats having received all reinforced trials at the beginning of training, or interspersed among non-reinforced trials. No significant spontaneous recovery was observed after a 1-day test delay. These results, which may be of clinical relevance with respect to relapse after therapy, are explained in terms of the training schedules generating differences in strength of inhibitory associations, and a relatively long, but not a short, test delay attenuating these associations.

Two experiments with rats examined behavioural control by feature stimuli in appetitive conditioning using latency of food-magazine visits as the dependent measure. In experiment 1, a feature-positive (FP) discrimination was presented in which a target stimulus was consistently followed by food when preceded by a serial feature and accompanied by a simultaneous feature, and not followed by food when presented alone. The reverse condition, a feature-negative (FN) discrimination procedure, was in effect in experiment 2. Groups of rats differed in the physical identity of the stimuli used as target and features. In the FP discrimination, all groups came to respond faster on reinforced than on nonreinforced trials. Subsequent tests revealed that the serial feature was responsible for this performance in all groups, whereas the simultaneous feature had not acquired significant control in all groups. Only one half of the groups solved the FN discrimination and they did this on the basis of only the simultaneous feature, which was a relatively intense stimulus in these groups. These results suggest a propensity to use the serial feature in FP discriminations and the simultaneous feature in FN discriminations.

We determined MDA's effects on: 1. (a) conditioning of the rabbit's jaw movement response (JMR) (Experiment 1) 2. (b) nonassociative JMRs and unconditioned JMRs (Experiment 2). Rabbits were administered 3,4-methylene-dioxyamphetamine (MDA; 0, 2, or 4 mg/kg) into the marginal ear vein 20–30 min prior to each of 10 daily sessions. Experiment 1 involved 30 daily training trials of 15 tone- and 15 light-conditioned stimuli (CSs) paired with a 1-ml squirt of water, as the unconditioned stimulus (UCS), injected into the oral cavity. The study revealed that MDA impaired conditioned response (CR) acquisition to tone-CS trials while augmenting CRs to light-CSs. In Experiment 2, the animals received 15 tone- and 15 light CS-alone and 30 UCS-alone presentations daily. The study revealed that MDA produced a modest increase in nonassociative responses over days that interacted with CS modality. Accordingly, these nonassociative effects could not account for MDA's influences on CR acquisition. Moreover, MDA's decrementing and enhancing of CRs to tone- and light-CSs, respectively, appears to be attributable to the drug's enhancing or decrementing tone- and light-CS intensity.

Fourteen Arabian foals were used to determine if a one-trial appetitive conditioning task, developed for laboratory rats, could be adapted for use in equine learning research. The learning apparatus consisted of a 1.5 m × 0.6 m wooden grid containing 40 compartments. Seven foals received a complete learning test which consisted of placing a foal in a pen with the learning apparatus on one wall, recording the foal's behavior for 5 min and then placing a food reinforcer in a target compartment (TC). After location of the food, the foal's behavior was recorded for an additional 5 min. Total visits made to the apparatus and compartments visited by the foal were recorded. The remaining seven foals received a test in which no reinforcer was placed in the TC. These foals were re-tested the next day with reinforcement. After location of the food reinforcer, all foals exhibited more visits to the apparatus, visits to the TC, visits one compartment from the TC, and visits greater than one and less than or equal to two compartments from the TC (P

RATIONALE: It is generally assumed that cue-reactivity results from appetitive pavlovian learning. This is the reason for applying cue exposure with response prevention interventions in the treatment of substance and eating disorders. However, not all appetitive conditioned responses are equally sensitive to extinction. Additionally, impulsivity traits appear to moderate cue-reactivity. Nevertheless, there has been little research on the role of impulsivity traits in the learning of different appetitive response systems. OBJECTIVES: The purpose of the present study was i) to replicate Van Gucht et al.'s (2010) findings, in particular, the acquisition and the differential extinction of appetitive learned responses and ii) to investigate the role of impulsivity traits in appetitive learning. METHODS: Participants (n = 50) took part in a single laboratory session. Impulsivity traits (reward sensitivity, response inhibition, sensation seeking) were measured at the beginning of the session. A paradigm similar to Van Gucht et al.'s (2010) was used for the acquisition and extinction of subjective conditioned responses for milk chocolate (craving, expectancy, and liking). RESULTS: The acquisition of appetitive responses was successful. Unlike craving and liking, the extinction of expectancy was fully successful. Impulsivity traits played no role in the acquisition and extinction of appetitive conditioning. CONCLUSIONS: The results support the differential sensitivity of different appetitive response systems to extinction. The lack of findings for the role of impulsivity traits in appetitive learning shows that the question of how impulsivity affects appetitive behaviour still remains open. Theoretical and methodological issues and clinical implications of the findings are discussed.

Three experiments explored the effects of response dependent stimuli which have had different types of contingent relationships with positive reinforcement. Results showed consistent differences in the effects of response dependent appetitive Pavlovian CS + s, CS − s, and truly random control (TRC) stimuli on the acquisition of a new response. These differences were shown in both a free operant and a discrete-trial learning situation. Appetitive Pavlovian CS−s consistently produced lower levels of responding than did TRC stimuli, even in an experimental situation free of possible contrast effects. The results of these experiments extended a contingency analysis of acquired associations to appetitive conditioning and provided a clear demonstration of a conditioned reinforcement effect against a variety of control procedures.

To examine time-dependent recovery from ECS-induced amnesia, 44 hooded rats were trained to leverpress for food. On treatment day the first leverpress was followed by footshock and ECS or sham ECS (SECS). Animals in both treatment conditions then experienced a 10-min extinction session either 1 or 3 days following treatment. For both the 1-day and 3-day delay ECS groups, the latencies to the first response during extinction were lower than the latencies of the corresponding SECS groups. When extinction followed treatment by 1 day, the ECS rats also made more responses during the test than the SECS rats; however, when tested 3 days after treatment, the ECS and SECS groups did not differ on extinction response rate. In this operant setting, therefore, time-dependent recovery from amnesia can be demonstrated with response rate as the amnesia measure. In addition, since both groups of SECS animals exhibited significant interrelationships of measures following treatment and the same measures were not associated in the ECS groups, it was hypothesized that the proactive effects of ECS include a reduction in the stability of performance.

•Experiment I studied ihe effect of several Pavlovian appetitive conditioning procedures on rats' headpoking into a food tray (goal tracking). The procedures included forward delay conditioning, CS-alone extinction, differential condition­ ing, and simultaneous compound conditioned inhibition training. In general. the head poke behaved in all of these treatments much like a Pavlovian CR; however. one couid also say that the headpoke behaved like· an adventitiously reinforced operant for which the CS was an S 0 • Experiment 2. therefore. used the differential-nondifferential technique (E. Gamzu & D. R. Williams. Science, 1971, 171, 923-925), and Experiment 3 used an omission technique (F. D. Sheffield, in W. F. Prokasy. Ed .. Classical conditioning, New York: Appleton­ Century-Crofts. 1965; D: R. Williams & H. Williams. Journal ofthe Experimema/ Analysis of Behavior, 1%9, U, 511-520), to try to separate the role of stimulus­ reinforcer and response-reinforcer relations in controlling the headpoke. These techniques proved inadequate. The results of Expe.riment2 could be given either operant or Pavlovian interpretations. Those of Experiment 3 showed that head­ poking is dominated by response-reinforcer, rather· than by stimulus-reinforcer. relations when the t\VO compete but forced no conclusion about which dominates when the two act together as in acquisition. Implications for pigeon autoshaping are discussed.

In Experiment I acquisition and extinction of instrumental escape conditioning with rats (N = 64) were studied as a function of reinforcement magnitude under conditions of partial and continuous reinforcement. In Experiment II the effects of partial and continuous reinforcement were studied in rats (N = 96) during acquisition followed by small, medium, and large reductions in reinforcement magnitude. A water-tank escape apparatus was used with temperature as the relevant variable. It was found that (1) with large reinforcement magnitude a continuously reinforced group was superior in acquisition to one that was partially reinforced; there were no differences with small reinforcement; (2) disruptive effects of a nonreinforced trial (a) appear early in learning, (b) are quite strong after each nonreinforced trial, and (c) persist through several succeeding reinforced trials; (3) major competing behaviors persist throughout acquisition for small reinforcement magnitude regardless of schedule, decline with large reinforcement (more so with continuous than with partial), and return to a high level in extinction for all conditions; (4) the partial reinforcement extinction effect occurs after large reinforcement but not after small, and it appears only with large reductions in reinforcement magnitude which approach extinction conditions. Only the first part of the last finding appears to be consistent with the appetitive conditioning literature.

A study conducted to determine the effects of level of water deprivation (30 cc, 90 cc, 180 cc, or ad lib daily water availability) on classical appetitive conditioning of jaw movement in the rabbit revealed that: (a) frequency of jaw movement CRs varied as a direct function of deprivation level; (b) frequency of jaw movement responses in unpaired control groups varied as a direct function of deprivation level, but at levels substantially lower than their respective experimental groups; (c) spontaneous responding was not differentially affected by deprivation level, but remained at a constant, low level throughout training; and (d) frequency of UCR occurrence varied as a direct function of deprivation level.

Continuous, random 50%, and single alternation (SA) schedules of reinforcement were employed in an investigation of classical appetitive conditioning of the jaw movement response in the rabbit. It was found that: ( a ) random 50% and SA reinforcement schedules led to lower levels of acquisition performance than continuous reinforcement; ( b ) evidence of response patterning to the SA schedule appeared only within and not across acquisition sessions; and ( c ) extinction performance decreased at a faster rate under continuous than under the partial reinforcement schedules. The findings are discussed with regard to Spence's (1960) account of partial reinforcement effects in instrumental reward conditioning, and Capaldi's (1966) sequential hypothesis of partial reinforcement extinction effects.