Potentiation of odor by taste in rats: Tests of some nonassociative factors.

Three experiments with 94 male Sprague-Dawley rats tested the contribution of nonassociative neophobia and sensitization to the potentiation of odor by taste. In Exp I, neophobia for almond odor (O), saccharin taste (T), and odor-taste compound (OT) cues was tested before and after noncontingent LiCl poisoning and compared with conditioned aversions produced by OT–LiCl temporal pairing. The OT compound potentiated unconditioned neophobia, but there was no evidence of poison-enhanced neophobia, disinhibition of neophobia, or sensitization by noncontingent LiCl; temporal pairing produced aversions for the compound and its elements. In Exp II, generalization to a novel odor was tested after O–LiCl or compound OT–LiCl pairing. The potentiated odor aversion did not generalize to the novel odor; it was specific to the odor paired with taste and LiCl. In Exp III, potentiation of the odor component by a discriminant or nondiscriminant taste component was tested. Potentiation was evident only when a novel discriminant taste was in compound with odor prior to LiCl poisoning. Results from all experiments support an associative "indexing" hypothesis of the potentiation effect in rats. (14 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Taste potentiation of poisoned odor by temporal contiguity.

Investigated the synergistic interaction between odor and taste in flavor-toxicosis conditioning in 2 experiments with 85 male Sprague-Dawley rats, in which the temporal interval between a 2-min odor and a 2-min taste was varied for thirsty Ss licking at a water spout. In Exp I (34 Ss), taste was presented at 0 min, and odor was presented at –20, –2, 0, 1, and 10 min to independent groups in a simple compartment. In Exp II (51 Ss), taste was presented at 0 min, and odor was presented at –5, –2, and 0 min in a wind-tunnel apparatus. Results indicate that odor alone was an ineffective CS for a toxic UCS under the conditions of the present experiments. Simultaneous (0-min) presentation of odor with taste potentiated the odor component so that it became more effective than the taste component. A 2-min interval between odor and taste attenuated potentiation, and a 5-min interval disrupted the effect. The interaction was asymmetrical; odor had no systematic effect on the conditioning of taste. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Potentiation of latent inhibition.

Rats were given exposure either to an odor (almond) or a compound of odor plus taste (almond plus saline), prior to training in which the odor served as the conditioned stimulus. It was found, for both appetitive and aversive procedures, that conditioning was retarded by preexposure (a latent inhibition effect), and the extent of the retardation was greater in rats preexposed to the compound (i.e., latent inhibition to the odor was potentiated by the presence of the taste). In contrast, the presence of the taste during conditioning itself overshadowed learning about the odor. We argue that the presence of the salient taste in compound with the odor enhances the rate of associative learning, producing a rapid loss in the associability of the odor. This loss of associability will generate both overshadowing and the potentiation of latent inhibition that is observed after preexposure to the compound. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Representation-mediated overshadowing and potentiation of conditioned aversions.

Examined the ability of CS-evoked representations of flavored substances to modulate the conditioning of LiCl-based aversions to simultaneously presented flavors or odors. In Exps I–III, 156 thirsty Sprague-Dawley rats first received pairings of an auditory CS with a flavored-water UCS; they then received pairings of a compound stimulus with a toxin. Exp IV examined the potentiation of aversion conditioning to a novel odor using 32 Ss. In Exp I, conditioning of a flavor was partially overshadowed when it was presented in compound with a tone that had been previously paired with another flavor. Exp II replicated that result and also found that conditioning to a flavor was not overshadowed when the flavor was presented in compound with a tone that had been paired with that same flavored substance. In Exps III and IV, conditioning to an odor stimulus was potentiated when it was presented in compound with either a tone or another odor that had been previously paired with a flavor stimulus. Results suggest that evoked representations of stimuli may substitute for those events themselves in a variety of associative functions. (36 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Conditioned taste and taste-potentiated odor aversions in the Syracuse high- and low-avoidance (SHA/Bru and SLA/Bru) strains of rats (Rattus norvegicus).

SHA/Bru and SLA/Bru rats were selectively bred for good and poor active-avoidance learning. However, SLA/Bru animals are superior to SHA/Bru rats in conditioned suppression and passive avoidance learning. In this experiment, saccharin taste and almond odor were the components of a compound CS (flavor) in an illness-induced aversive conditioning paradigm. SLA/Bru rats (n?=?17) showed stronger conditioned flavor, taste, and odor aversion than did SHA/Bru animals (n?=?18). Unselected Long-Evans rats (n?=?18) were intermediate between the selected strains. SLA/Bru and Long-Evans rats showed taste-potentiated odor aversion in this experiment, whereas SHA/Bru animals did not. The results provide evidence that genetic factors, as exemplified by the different strains, are importantly involved in the mechanisms underlying interoceptive and exteroceptive aversive conditioning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Temporal dynamics of the rabbit's nictitating membrane response in serial compound conditioned stimuli.

Two experiments, with 88 female albino rabbits, investigated conditioning of the nictitating membrane response to a reinforced serial compound stimulus. The serial compound was composed of a 400-msec CS (CSA), a trace interval of at least 2 sec, and a brief 2nd CS (CSB) prior to the UCS. The CSB duration was either 150, 250, or 400 msec in Exp I, and the CSB duration in Exp II was 400 msec. Exp I compared serial compound training to an "uncoupled" condition, which contained intermixed CSA–UCS trials and CSB–UCS trials. Exp II compared serial compound training with uncoupled training, 2nd-order conditioning (CSA–CSB/CSB–UCS), trace conditioning (CSA–UCS), and generalization testing that entailed CSB–UCS training and unreinforced tests with CSA. The serial compound, uncoupled, and 2nd-order conditioning procedures all produced high levels of responding during CSA, but only the reinforced serial compound procedure yielded an appreciable likelihood of CR initiation during the trace interval between CSA and CSB. The CRs during the trace interval were temporally distinct from the CRs during CSA and did not appear to be belated CRs to CSA itself. Results are discussed in connection with stimulus selection phenomena, for example, overshadowing and potentiation of toxicosis conditioning. (46 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Carbohydrate-conditioned odor preferences in rats.

The effectiveness of odor cues to support nutrient-conditioned flavor preferences in rats was studied. When the rats drank fluid, the CS+ odor was paired with intragastric (IG) infusions of Polycose, and the CS– odor with IG water. In Experiment 1, rats trained with almond and anise odors presented with plain drinking water failed to acquire a CS+ odor preference. In contrast, rats in Experiment 2 formed a strong aversion to anise (or almond) paired with lithium chloride, which indicated that the odors were distinguishable to the rats. Experiment 3 showed that providing unique tastes (bitter or sour) in combination with the odors during training potentiated odor conditioning. The rats displayed a strong preference for the odor?+?taste CS+ and for the odor component alone. Experiment 4 showed that with another pair of odors (peppermint and vanilla), CS+ preferences could be conditioned in the absence of taste cues during training. These results demonstrate that rats can acquire strong nutrient-conditioned odor preferences. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A comparison of taste aversions induced by radiation and lithium chloride in CS-US and US-CS paradigms.

Describes 3 experiments with a total of 454 albino male Charles-River rats. Conditioned taste aversions induced by ionizing radiation and lithium chloride (LiCl) were compared with both forward (CS-UCS, conditioned stimulus-unconditioned stimulus) and backward (UCS-CS) conditioning paradigms. Taste aversions were produced when a saccharin CS preceded or followed a 100-r radiation UCS by as much as 6 hrs, but a 2%-of-body-weight, .15-mol LiCl UCS was effective only in CS-UCS pairings. It is argued that the ineffectiveness of an LiCl stimulus in UCS-CS pairings was not attributable to differences in the "strength" of the respective LiCl and radiation doses in that these doses yielded comparable aversions in forward pairings. These results are related to inadequacies of a "sickness" model of taste aversion conditioning. (22 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Simultaneous conditioning in honeybees (Apis mellifera).

Honeybees were classically conditioned with odor as conditioned stimulus/stimuli (CS), sucrose as unconditioned stimulus/stimuli (UCS), and proboscis extension as response. The purpose of Exp 1 (Ns?=?26 and 27) was to look for facilitation of forward conditioning by CS–UCS overlap, but rapid conditioning without overlap left little room for improvement. In 2 further experiments, CS and UCS were simultaneous, and response to odor alone was measured in subsequent tests. In Exp 2, a simultaneous group (N?=?25) responded more to the training odor than did an unpaired control group (N?=?25). In Exp 3, a differentially conditioned simultaneous group (N?=?29) responded more to an odor paired with sucrose in training (S+) than to an odor presented alone (S–). The implications of the results for the problem of the role of amount of reward in honeybee learning are considered. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Taste-potentiated odor aversion learning based on amphetamine

This study sought to determine whether a taste can potentiate a conditioned odor aversion based on amphetamine as well as those based on lithium. A taste-potentiated odor aversion (TPOA) based on lithium was obtained in Experiment 1 only with a low concentration of an almond odor. This concentration was used in Experiment 2 where the taste, 0.1% saccharin, potentiated an odor aversion based on 1 mg/kg d-amphetamine. This was replicated in Experiment 3 where potentiation was found with doses of both 1 and 3 mg/kg amphetamine, and no effect of dose was detected. It was concluded that TPOA learning is not restricted to drugs such as lithium that produce conditioned unpalatability as well as conditioned aversions to a taste, because amphetamine does not produce conditioned unpalatability at the doses used here. Furthermore, because in Experiment 3 postconditioning extinction of the saccharin aversion removed the potentiation effect, it appears that this form of TPOA may depend on an association between the odor and taste, as proposed by within-compound theory.     

Acquisition of conditioned associations in Hermissenda: Additive effects of contiguity and the forward interstimulus interval.

Examined conditioned suppression of photokinesis (CSPK) by the marine mollusc in 3 experiments. In each experiment, groups of Ss received light (conditioned stimulus, CS) paired with high-speed orbital rotation (unconditioned stimulus, UCS), light and rotation explicitly unpaired, or no exposure to these stimuli. 24 hrs after training, all Ss were tested for CSPK in the presence of the light. 50 CS–UCS pairings resulted in a marginal CSPK, whereas 100 and 150 pairings produced strong CSPK. In Exp 2, delay between CS onset and UCS onset was varied between 1 and 10 s. The 10-s interstimulus interval (ISI) did not support conditioning, whereas 1-s and 2-s ISIs were effective. In Exp 3, CS–UCS pairings in which the CS preceded the onset of the UCS and ended with the offset of the UCS evoked stronger CSPK than either a CS that preceded the UCS and ended with its onset or a CS that was paired in simultaneous compound with the UCS. CS–UCS contiguity and the forward ISI act additively to establish the CS–UCS association. No differences were observed between groups that were untreated and that received the CS and UCS unpaired. Similarities are noted in the temporal characteristics of associative learning in these Ss and vertebrate species. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Flavor-illness aversions: Gustatory neocortex ablations disrupt taste but not taste-potentiated odor cues.

Two studies evaluated the contribution of the gustatory neocortex (GN) to the potentiation of odor by taste during illness-induced aversions in 130 male Sprague-Dawley rats. In Exp I, Ss lacking GN and controls were given an odor, a taste, or an odor–taste compound cue followed by intragastric gavage of LiCl. Prior to conditioning, neophobia for flavored solutions was absent in Ss with GN lesions. After pairing with LiCl, GN Ss developed normal conditioned odor aversions, whereas conditioned taste aversions were attenuated or totally blocked. Potentiation of odor by taste after compound conditioning was evident in both control and GN Ss. In Exp II, normal Ss were given compound conditioning to induce potentiated odor aversions and then given GN lesions prior to tests with the odor and taste components. Taste aversion retention was totally disrupted by GN ablation; potentiated odor aversions were retained by both groups, although the GN group extinguished faster. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Malleability of conditioned associations: Path dependence.

Using conditioned suppression of barpressing to investigate the stability of a conditioned stimulus–unconditioned stimulus (CS–UCS) association, the present authors gave 151 water-deprived rats either a few pairings of the CS with a strong footshock UCS or many pairings with a weak footshock UCS so that barpress suppression in response to CS was equated. Exp I established training parameters that yielded this equivalence. Specifically, rapid acquisition to a preasymptotic level of responding with strong shock produced suppression comparable to the asymptotic level reached more slowly with weak shock. Exp II showed that although equivalent performance was obtained from extensive conditioning with a weak shock or limited conditioning with a strong shock, only extensive conditioning with weak shock resulted in retarded acquisition of an association between that same CS and a footshock level perceived as midway between the 2 initial training shock intensities as implied by asymptotic performance in Exp I. Exp III demonstrated that the observed retardation in Ss given many conditioning trials with weak shock was CS-specific. It is concluded that the malleability of learned behavior is not simply a function of initial associative strength but is dependent on the path during initial acquisition. (18 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Role of temporal order and odor intensity in taste-potentiated odor aversions.

The role of the temporal order of odor and taste was studied in two experiments, and a third experiment studied the role of odor intensity in flavor-toxicosis conditioning with thirsty rats licking water spouts in a "wind tunnel." In all experiments, odors and tastes were presented for 2 min to rats, and 30 min later, a toxin (lithium chloride) was intubated. In Experiment 1, an odor was presented 90 s before, during, or 90 s after a taste to independent groups. Experiment 2 was a within-subjects partial replication of the first. Each rat was presented with one odor, then a taste, then a second odor with each stimulus separated by 45 s. The results of Experiments 1 and 2 indicated that (a) odor alone is not associated with illness under our conditions, (b) presenting an odor and a taste at the same time potentiates the odor component so that it is associated with illness, (c) 45-s and 90-s intervals between odor and taste eliminate potentiation, and (d) taste and odor interact asymmetrically; that is, odor has little effect on the development of taste-illness associations. In Experiment 3, an odor and a taste were presented simultaneously, and odor intensity varied. As odor intensity increased, the strength of the taste-potentiated odor aversion increased, whereas the aversion to the taste remained constant. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Overshadowing and summation in compound stimulus conditioning of the rabbit's nictitating membrane response.

Examined acquisition of the rabbit's nictitating membrane response to a light?+?tone simultaneous compound stimulus and its components as a function of the intensity of the tone. In Exp I, the tone intensity was varied across the values of 85, 89, and 93 db, and the CS–UCS interval was 400 msec. In Exp II, the tone intensities were 73, 85, and 93 db, and the CS–UCS interval was 800 msec. Exps III and IV further examined the effects of the 73-db CS–UCS tone at CS–UCS intervals of 400 and 800 msec. All experiments included control groups, which were trained with either a light or a tone CS. Overall results show repeated instances of overshadowing: the impairment of CR acquisition to one or both of the components of a compound. Two types of summation were obtained: within-Ss summation, in which Ss trained with a compound showed a higher level of responding to the compound than to either of its component CSs; and between-groups summation, in which a group trained with a compound showed faster CR acquisition than either of its corresponding control groups trained with a single CS. Results are discussed in terms of perceptual and distributive processing models of compound stimulus conditioning. (37 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Human blink startle during aversive and nonaversive Pavlovian conditioning.

Potentiation of blink startle during aversive and nonaversive Pavlovian single-cue conditioning was assessed in human Ss. In Exp 1 (N?=?89), the conditioning group received paired presentations of a visual CS and an unconditioned stimulus/stimuli (UCS), whereas the control group was presented with a random sequence. The UCS was an electric shock for half the Ss and a nonaversive reaction time (RT) task for the other half. Electrodermal conditioning was evident regardless of the nature of the UCS, but blink potentiation was found only in the conditioning group that had been trained with the aversive UCS. These results were replicated in Exp 2 (N?=?65), in which a nonaversive UCS of increased motivational significance was used. Thus, only aversive conditioning seems to affect the affective valence of the CS, at least as reflected by changes in a skeletal reflex. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Element pretraining influences the content of appetitive serial compound conditioning in rats.

Examined the effects of prior pairings of conditioned stimulus/stimuli (CS)2 with the unconditioned stimulus/stimuli (UCS) on the nature of the associations formed in CS1?→?CS2?→?UCS serial compound conditioning, in 4 experiments with 72 male and 32 female albino rats. In Exps I and II, prior training of CS2 prevented the acquisition of stimulus–stimulus (S–S) associations between CS1 and stimulus features of CS2 but enhanced the acquisition of stimulus–response (S–R) associations between CS1 and the emotional conditioned response (CR) evoked by CS2. In Exps III and IV, the effects of CS2 pretraining were not due to CS2 training itself, but rather to its endowing CS2 with the ability to evoked a strong CR during the early stages of serial compound conditioning. In Exp III, suppression of the CR to a pretrained CS2 during serial compound conditioning permitted the establishment of S–S associations. In Exp IV, the induction of a CR in the presence of an untrained CS2 during serial compound conditioning prevented the acquisition of S–S associations. (31 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Motivational state regulates the content of learned flavor preferences.

Rats acquired a preference for an aqueous odor (almond) presented in simultaneous compound with sucrose. Separate presentations of saccharin reduced this preference in rats with ad-lib access to food during training or at test, but not in rats that were hungry during both training and test. In contrast, separate presentations of sucrose reduced the preference for the almond irrespective of deprivation state during training and test. We interpret the results to mean that a hungry rat forms odor–taste and odor–calorie associations, and its motivational state on test determines which of these associations controls the preference. In contrast, a rat that is not hungry during training only forms an odor-taste association, and its performance on test is independent of its level of hunger. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Function of the "onset of illness" in the preference changes of alloxan-diabetic rats.

144 male Sprague-Dawley rats were given access to saccharin or NaCl solutions as a conditioned stimulus (CS) at 1 of several times before and after injection with alloxan as an unconditioned stimulus (UCS) and were compared with controls (given UCS but no CS exposure) on their preference for the CS 7 days after the diabetes was well established. Results indicate that Ss exposed to the UCS at 1 or 2 hrs prior to the CS or at 1, 2, or 6 hrs following the CS all formed a conditioned aversion, whereas those with 6, 24, or 48 hrs between UCS and CS showed no greater aversion to the CS than controls. It is suggested that while the onset of alloxan diabetes can serve as the UCS for a conditioned taste aversion, the behavior of alloxan-diabetic rats towards saccharin does not depend upon this process. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Classical conditioning of proboscis extension in honeybees (Apis mellifera).

Conditioned extension of the proboscis in restrained honeybees with odor as the CS and sucrose solution—delivered to the antenna (to elicit extension of the proboscis) and then to the proboscis itself—as the UCS. In a 1st series of experiments, acquisition was found to be rapid, both in massed and in spaced trials; its associative basis was established by differential conditioning and by an explicitly unpaired control procedure. Both extinction and spontaneous recovery in massed trials were demonstrated. In experiments on the nature of the UCS, eliminating the proboscis component lowered the asymptotic level of performance, whereas eliminating the antennal component was without effect; reducing the concentration of sucrose from 20% to 7% slowed acquisition but did not lower the asymptotic level of performance; and second-order conditioning was demonstrated. In experiments on the role of the UCS, an omission contingency designed to eliminate adventitious response-reinforcer contiguity was found to have no adverse effect on acquisition. In experiments designed to analyze the resistance to acquisition found after explicitly unpaired training in the 1st experiments, no significant effect was found of prior exposure either to the CS alone or to the UCS alone, although the unpaired procedure again produced resistance that was shown to be due to inhibition rather than to inattention; extinction after paired training was found to be facilitated by unpaired presentations of the UCS. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)