Context conditional flavor preferences in the rat based on fructose and maltodextrin reinforcers.

In three experiments, rats were exposed to a flavor preference procedure in which flavor A was paired with the reinforcer and flavor B presented alone in Context 1, while in Context 2 flavor A was presented alone and flavor B with the reinforcer. With fructose as the reinforcer both two- and one-bottle training procedures produced a context-dependent preference (Experiments 1 and 2). With maltodextrin as the reinforcer two-bottle training produced a context-dependent preference (Experiment 1). Following one-bottle training with maltodextrin reinforcement rats demonstrated a context-dependent preference when the conditioned stimulus (CS)- was presented with a dilute solution of the reinforcer during training (Experiment 3B) but not when the CS- was presented alone (Experiments 2 and 3A). The pattern of results with maltodextrin reinforcement suggests that there was competition between the cue flavors and the taste of the maltodextrin as predictors of the postingestive consequences of the maltodextrin reinforcer. The fact that rats were able to display context-dependent flavor preferences is consistent with the idea that learned flavor preferences rely on the sort of cue-consequence associations that underpin other forms of conditioning which produce accurate performance on biconditional tasks. The differences between fructose- and maltodextrin-based preferences are discussed in terms of configural and elemental learning processes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reinforcer devaluation in palatability-based learned flavor preferences.

Rats exposed to simultaneous compounds of 1 neutral flavor with dilute (2%) sucrose and a 2nd flavor with dilute (2%) maltodextrin subsequently consumed both flavors in preference to a 3rd flavor that was never paired with a palatable taste. Brief training exposure under ad lib food and water minimized the postingestive effects of nutrients, emphasizing the contribution of palatability to these preferences. Devaluation of sucrose or maltodextrin by pairing with illness (Experiment 1) or sensory-specific satiety (Experiment 2) selectively reduced the preference for the flavor previously paired with the devalued reinforcer. Such reinforcer-specific devaluation effects suggest that palatability-based learned flavor preferences are underpinned by a Pavlovian process whereby the cue flavor is associated with the taste of the concurrently consumed palatable reinforcer. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Flavor preferences produced by backward pairing with wheel running.

In 3 experiments rats given 8 sessions of preexposure to wheel running acquired a preference for a flavor that was given immediately after each of 4 subsequent sessions of wheel running. Such flavor preference was less likely when rats were given the same conditioning procedure but without preexposure to wheels (Experiment 1) or when access to flavor was delayed by 30 min following a wheel session (Experiment 2). When rats were given a flavor before each wheel session, the resulting conditioned aversion was greater in rats that had no prior exposure to wheel running (Experiment 3). These results show that whether an aversion or preference for a flavor is produced by wheel running depends on an interaction between prior wheel experience and the sequence of events. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Flavor preferences conditioned by intragastric nutrient infusions in rats fed chow or a cafeteria diet

Numerous studies demonstrate that chow-fed rats learn to prefer flavors that are associated with the postingestive effects of nutrients. The rats> limited dietary experience (i.e. only lab chow) may have facilitated preference learning because of the novelty of the training stimuli. This possibility was investigated by comparing nutrient conditioning in rats fed chow or a varied "cafeteria" diet. Rats in Experiment 1 were trained during alternate sessions (30 min/day) to drink two different flavors paired with concurrent intragastric infusions of 16% Polycose or water. Both diet groups displayed similarly strong preferences (89%) for and increased acceptance of the Polycose-paired flavor. A more demanding learning task was used in Experiment 2: new flavors were paired with delayed (15 min) infusions of Polycose or water. The chow and cafeteria groups both showed reduced, but comparable (78%, 77%) preferences for the Polycose-paired flavor. In Experiment 3, new flavors were paired with concurrent infusions of 7.1% corn oil or water. Again, the cafeteria and chow groups developed similar preferences for the nutrient-paired flavor (85%, 78%). Also, both groups preferred the Polycose-paired flavor of Experiment 1 to the oil-paired flavor of Experiment 3 (76%, 78%). These results indicate that dietary variety does not interfere with nutrient-conditioned flavor preference learning in rats.     

Effects of lesions to the hippocampus on contextual fear: Evidence for a disruption of freezing and avoidance behavior but not context conditioning.

The effects of ibotenic lesions of the hippocampus on conditioning to contextual cues during classical fear conditioning in rats were evaluated by (a) the amount of freezing elicited by contextual cues and (b) the relative avoidance of a shock compartment. In Experiment 1, lesions to the hippocampus had no effect on contextual freezing and marginally affected avoidance after repeated sessions. Experiment 2 showed that lesions to the hippocampus disrupted avoidance when tested after a single conditioning session, while leaving unaffected the acquisition of contextual freezing. Experiment 3 indicated that these lesions decreased the acquisition of contextual freezing when higher footshock intensity was used but had no effect on avoidance after repeated conditioning sessions. These results show that freezing and avoidance do not quantify context conditioning similarly. They further indicate that lesions to the hippocampus may disrupt the expression of these behaviors used as measures of context conditioning but not the acquisition of context conditioning per se. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Area postrema lesions impair flavor-toxin aversion learning but not flavor-nutrient preference learning.

Rats with lesions of the area postrema. (APX) or sham lesions were trained to associate flavored solutions with positive or negative postingestive consequences. The APX rats were similar to controls in learning preferences for flavors paired with concurrent intragastric infusions of maltodextrin or corn oil and for a flavor paired with delayed maltodextrin infusions. In contrast, the APX rats displayed impaired aversion learning for flavors paired with toxic drug treatments (lithium chloride infusion or methylscopolamine injection). The aversion learning deficit ranged from mild to total, depending on training procedures. These findings confirm the important role of the area postrema in flavor-toxin learning but provide no evidence for its involvement in flavor-nutrient conditioning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

"Cue interactions in flavor preference learning: A configural analysis": Correction to Dwyer et al. (2011).

Reports an error in "Cue interactions in flavor preference learning: A configural analysis" by Dominic M. Dwyer, Mark Haselgrove and Peter M. Jones (Journal of Experimental Psychology: Animal Behavior Processes, 2011[Jan], Vol 37[1], 41-57). There was an error in Figure 3. The X-axis of both panels of this figure should be labeled “3-trial block” and not “trial.” The analysis of the simulations presented in Figure 3 are unaffected by this change. The corrected figure is provided in the erratum. (The following abstract of the original article appeared in record 2011-01268-001.) Four experiments showed that the preference normally established to a neutral flavor cue that was paired with maltodextrin was attenuated when that cue was conditioned in compound with another flavor—overshadowing. Furthermore, two experiments showed that the preference for a neutral flavor conditioned as part of a compound was further attenuated if the other element in that compound was separately paired with the reinforcer—blocking. These results stand in contrast to a number of previous compound flavor preference conditioning experiments, which have not revealed reliable cue competition effects. These discrepant findings are discussed in terms of the effects of within-compound associations and a configural perspective on potentiation. Modeling of this configural perspective predicts that a compound of two separately trained cues will elicit a similar response to the individual cues themselves—absence of summation. Two experiments confirmed this prediction. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Odor of Taste Stimuli in Conditioned "Taste" Aversion Learning.

The present research addresses whether rats can express odor aversions to the odor of taste stimuli. In Experiment 1, saccharin or salt were either mixed in distilled water, so the rats could taste and smell them, or presented on disks attached to the tubes' metal spouts so the rats could only smell them. Aversions were established to taste stimuli under both conditions. The results of Experiment 2 indicate that conditioning was to the odor of the tastes when they were presented on disks in Experiment 1, hence both taste and odor aversions were established by means of "taste" stimuli. Taste aversion learning thus may more properly be termed flavor aversion learning, with flavor referring to both taste and odor components. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Conditioned flavor preference and aversion: Role of the lateral hypothalamus.

Food-restricted rats with ibotenic acid lesions of the lateral hypothalamus (LH) and sham controls were trained to associate flavored solutions with positive or negative postingestive consequences. The LH rats learned to prefer a flavor that was paired with concurrent intragastric infusions of maltodextrin. Unlike controls, the LH rats failed to learn a preference for a flavor paired with delayed maltodextrin infusions and showed an attenuated preference for a flavor paired with concurrent fat infusions. The LH rats did not differ from controls in learning to avoid flavors paired with concurrent or delayed infusions of lithium chloride. These data indicate that the LH is not essential for all types of flavor-postingestive consequence conditioning but is critical for learning to associate flavors with delayed nutrient feedback. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Conditions Favoring Superconditioning of Irrelevant Conditioned Stimuli.

Three appetitive conditioning experiments with rats found partial learning of complex XA+ , XB+ , XAB- (+ stands for reinforced; - stands for unreinforced) negative patterning discriminations with intermixed A+ and B+ trials (Experiment 1). AB+ trials (Experiment 2), and A+ , B+ , and AB+ trials (Experiment 3). In all experiments, differential responding emerged more slowly during the learning of the negative patterning discriminations than during learning of the XA+ , XB+ , XC- control discriminations. Additionally, the negative patterning groups responded more to X than to a separately reinforced Y on unreinforced test trials: thus, X derived superexcitatory properties. This pattern was reversed in the control groups. Results are consistent with theories that allow for different activation patterns when elements are combined. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Pavlovian conditioning with ethanol and lithium: Effects on heart rate and taste aversion in rats.

20 female albino Simonsen rats received paired injections of either ethanol or saline as the CS and LiCl as the UCS in a Pavlovian differential conditioning paradigm. LiCl evoked a large deceleration in heart rate (80–200 beats/min) as a UCR. As a result of 10 conditioning trials, the substance paired with LiCl elicited a lower average heart rate than that elicited by the unpaired substance. Moreover, Ss that received ethanol–LiCl injections subsequently were more averse to the taste of ethanol than Ss receiving saline–LiCl pairings. However, there were no differences in ethanol's ability to serve as the UCS to induce an aversion to a novel flavor solution (i.e., the Avfail phenomenon was not observed). The overall pattern of results underscores the value of using multiple indexes of learning in drug–drug conditioning paradigms. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cerebellar stimulation as an unconditioned stimulus in classical conditioning.

Implanted rabbits with chronic stimulating electrodes in white matter underlying lobule HVI of the cerebellar cortex. Stimulation elicited movements of the face or neck and, when paired with a tone CS, produced learning comparable to that seen with peripheral unconditioned stimulus/stimuli (UCS). CS-alone trials produced extinction. Reinstatement of paired trials produced reacquisition with savings. Additional groups received either explicitly or randomly unpaired CS–UCS trials before paired conditioning. Low-frequency responding during these sessions indicated that the paired training results were associative and not due to pseudoconditioning or sensitization. Explicitly unpaired sessions retarded learning on subsequent paired trials compared with groups that received either randomly unpaired or no CS–UCS preexposure. These results are interpreted in terms of the role of the cerebellum and associated pathways in classical conditioning of motor responses. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of telencephalic NO and cGMP in avoidance conditioning in goldfish (Carassius auratus).

Our previous study with N-methyl-D-aspartate (NMDA) receptor antagonist D-AP5 suggested that NMDA receptors were involved in learning but not memory consolidation of avoidance conditioning. The present study investigated whether nitric oxide (NO) and cyclic guanosine monophosphate (cGMP) were involved in memory consolidation but not learning of avoidance conditioning in goldfish. Experiments 1 to 3 investigated amnestic and performance effects of NO inhibitor L-NAME and cGMP inhibitor LY-83583. Experiment 4 investigated whether posttraining intratelencephalic injection of NO donor SNAP ameliorated anterograde amnestic effects of pretraining NO inhibitor L-NAME. The results showed that L-NAME and LY-83583 produced significant anterograde and retrograde amnesia at doses that did not impair performance processes, and the drugs produced more severe retrograde than anterograde amnesia. Furthermore, posttraining SNAP significantly ameliorated anterograde amnestic effects of pretraining L-NAME. Thus, our previous results with D-AP5 and current results with L-NAME and LY-83583 together suggest that the NMDA receptors are involved in learning or the process that is completed during training, whereas the NO and cGMP are involved in memory consolidation or the process that is normally completed sometime following the learning experience. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Common toads (Bufo arenarum) learn to anticipate and avoid hypertonic saline solutions.

Toads (Bufo arenarum) were exposed to pairings between immersion in a neutral saline solution (i.e., one that caused no significant variation in fluid balance), followed by immersion in a highly hypertonic saline solution (i.e., one that caused water loss). In Experiment 1, solutions were presented in a Pavlovian conditioning arrangement. A group receiving a single neutral-highly hypertonic pairing per day exhibited a greater conditioned increase in heart rate than groups receiving either the same solutions in an explicitly unpaired fashion, or just the neutral solution. Paired toads also showed a greater ability to compensate for water loss across trials than that of the explicitly unpaired group. Using the same reinforcers and a similar apparatus, Experiment 2 demonstrated that toads learn a one-way avoidance response motivated by immersion in the highly hypertonic solution. Cardiac and avoidance conditioning are elements of an adaptive system for confronting aversive situations involving loss of water balance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

CS-US preexposure effects on trace eyeblink conditioning in young rats: Potential implications for functional brain development.

Recent studies of delay eyeblink conditioning (EBC) in young rats have demonstrated different effects of various conditioned and unconditioned stimulus (CS-US) preexposure conditions on learning at different ages. The present study extends this research to trace EBC. Subjects experienced 1 of 3 preexposure conditions (paired CS-US, unpaired CS-US, or no stimuli) at either 20 or 24 days of age. Four days later, they were conditioned using either trace (Experiment 1) or delay (Experiment 2) EBC parameters. Results were similar at both ages tested. Paired preexposure facilitated acquisition of delay but not trace relative to context preexposure. Unpaired preexposure impaired acquisition of both delay and trace. These behavioral findings provide a foundation for hypotheses about the functional maturation of cerebellar, hippocampal, and entorhinal learning circuits. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

CER suppression, passive-avoidance learning, and stress-induced suppression of drinking in the Syracuse high- and low-avoidance strains of rats (Rattus norvegicus).

The Syracuse strains of Long-Evans rats were selectively bred for good (SHA) or poor (SLA) avoidance learning in a two-way shuttle box, which resulted in a phenotypic difference that is correlated with behavior patterns indicative of emotional reactivity, SLA animals showing evidence of greater emotional reactivity than SHA animals. The first three experiments examined conditioned suppression of bar pressing and compared paired and unpaired conditioned- and unconditioned-stimulus presentations to evaluate the influence of conditioning versus primary aversive stimulation on baseline responding. SLA animals acquired conditioned suppression faster than SHA animals and also showed greater suppression of baseline responding than SHA animals. In Experiment 4, SLA animals learned a passive-avoidance task faster than SHA animals. In Experiment 5, SLA animals showed greater stress-induced suppression of drinking a weak quinine solution than SHA animals. These data are consistent with the hypothesis that SLA animals are more emotionally reactive than SHA animals. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Muscarinic receptor antagonism of the nucleus accumbens core causes avoidance to flavor and spatial cues.

Pharmacological blockade of muscarinic receptors in the nucleus accumbens reduces food intake and instrumental behaviors that are reinforced by food delivery. Nucleus accumbens muscarinic antagonism may specifically suppress the hedonic or reinforcing effects of food, thus blocking its capacity to direct behavior. Alternatively, muscarinic receptor blockade may cause a negative hedonic state that interferes with appetitive learning and food intake. In these experiments, rats received infusions of scopolamine methyl bromide (10 μg/0.5 μl) into the nucleus accumbens core, following exposure to a novel flavor of liquid diet (Experiment 1) or prior to being placed into a place preference apparatus (Experiment 2). In both experiments, nucleus accumbens muscarinic receptor antagonism caused subsequent avoidance of the paired cue (flavor or spatial location). This effect was specific to cholinergic manipulation; no conditioned taste avoidance was observed after pairing the novel flavor with nucleus accumbens core antagonism of N-methyl-D-aspartate, dopamine D?, or opioid receptors (Experiment 3). These experiments confirm previous reports of a critical role for striatal acetylcholine in modulating goal-directed behaviors, but suggest caution when interpreting behavioral effects of pharmacological manipulation of striatal acetylcholine. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Correlations between paradoxical sleep and shuttle-box conditioning in rats.

Eighteen male Wistar rats were given one daily two-way active avoidance conditioning session followed immediately by 5 hr of sleep recording, for 5 consecutive days. The group of rats that achieved 80% or greater avoidance in some of the 5 training sessions showed significant linear increases of paradoxical sleep (PS), compared with baseline levels, throughout the successive conditioning sessions. Furthermore, (a) the group of rats showing PS increases (more than 1 SD above baseline) after some of the training sessions achieved a significantly higher final number of avoidances than the remaining animals; (b) a high and positive correlation was observed between avoidance increases in the 3rd conditioning session and previous PS; and (c) maximum increases in correct performance often occurred following PS increases. It is concluded that PS increases facilitate the consolidation of learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stimulus Processing and Associative Learning in Wistar and WKHA Rats.

This study assessed basic learning and attention abilities in Wistar-Kyoto hyperactive (WKHA) rats using appetitive conditioning preparations. Two measures of conditioned responding to a visual stimulus, orienting behavior (rearing on the hind legs), and food cup behavior (placing the head inside the recessed food cup) were measured. In Experiment 1, simple conditioning, but not extinction, was impaired in WKHA rats compared with Wistar rats. In Experiment 2, nonreinforced presentations of the visual cue preceded the conditioning sessions. WKHA rats displayed less orienting behavior than Wistar rats but comparable levels of food cup behavior. These data suggest that WKHA rats exhibit specific abnormalities in attentional processing as well as in learning stimulus-reward relationships. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Modulation by the stimulus properties of excitation

Three experiments with pigeons investigated the role of excitation in a Pavlovian modulatory paradigm where the reinforcement contingencies of a conditioned stimulus (CS) were signaled by modulatory stimuli. In Experiment 1, excitatory training of the modulator that signaled reinforcement, the positive modulator, had a greater facilitative impact on discrimination learning than did excitatory training of both modulators. Although this could have resulted from simple excitatory summation, Experiment 2 revealed that excitatory training of the negative modulator also enhanced learning more than did excitatory training of both modulators. In Experiment 3, responding to CSs that had come under the control of differentially excitatory modulators was similarly controlled by new stimuli that had received simple differential excitatory training. Results suggest that excitation can play a modulatory role in Pavlovian conditioning.