Taste Aversion Learning Based on Swimming and Lithium Chloride Injection in Rats: Implications From Cross-familiarization Tests and Stimulus Selectivity1

In rats, swimming causes avoidance of the taste solution consumed immediately before the swimming. Several lines of research have shown that this taste avoidance reflects Pavlovian conditioned aversion based on correlations between the taste and swimming-induced nausea. The present research compared swimming-based taste aversion learning (TAL) with conventional TAL based on nausea-inducing lithium chloride (LiCl). By exploiting cross-familiarization techniques, Experiments 1A and 1B suggested that different physiological states are induced by swimming and LiCl. This claim was supported by Experiment 2, which reports stimulus selectivity in saccharin and sucrose aversions based on swimming and LiCl.     

Failure of sodium- and calcium-deficient rats to acquire conditioned taste aversions to the object of their specific hunger.

Attempts were made to condition taste aversions to the objects of two mineral-specific hungers. Both the innate preference of adrenalectomized rats for sodium and the learned preference of parathyroidectomized rats for calcium were studied. None of the sodium-deficient rats poisoned after drinking sodium chloride (NaCl) reached a taste-avoidance criterion, even after nine pairings of salt ingestion with aversive lithium chloride injections. Six of 11 calcium-deficient rats did not meet the salt-avoidance criterion after 10 pairings. Nondeficient control subjects learned to avoid these salt solutions completely after an average of only three such pairings. Besides unmasking a surprising degree of similarity between the learned and innate specific hungers studied, the results clearly demonstrate a powerful influence of physiological need on aversion conditioning.     

Formation of associations of colored and flavored food with induced sickness in five avian species

Domestic ducks, geese, pigeons, quail, and chickens were given colored, flavored, or colored and flavored food and then injected with lithium chloride. Each species showed learning of color and taste aversions. Flavor facilitated the formation of color aversions in ducks, geese, and pigeons but not in quail or chickens. Color interfered with the formation of flavor aversions in quail and chickens but not in the other three species. These findings indicate that all birds can probably associate both colored and flavored food with induced sickness and that colored food is more easily associated with induced sickness than is colored water. Moreover, these findings suggest that the capacity to associate colored and flavored food with induced sickness and the interaction between color and flavor in food vary between species. Birds, such as quail and chickens, that eat relatively tasteless food rely more on color than on flavor cues when forming learned food aversions. Birds that can select their food on the basis of taste, such as ducks and geese, rely more on flavor than on color when forming aversions to food. Birds, such as pigeons, that are initially raised on tasty food before switching to predominantly tasteless food show tendencies that are similar to those of ducks and geese.     

Selective associations in one-day-old rats: taste-toxicosis and texture-shock aversion learning

One-day-old rats learned aversions to a novel taste paired with lithium-induced distress and to a tactile stimulus paired with brief electric shocks. However, aversions did not develop when taste was paired with shock or when the tactile stimulus was paired with lithium treatment. The aversions occurred only when lithium treatment immediately followed taste exposure and when shock was concurrent with exposure to the tactile stimulus. These findings indicate that selective associations in aversion learning are mediated by innate mechanisms that govern conditioning in the absence of extensive ontogenetic experience. The present research also shows that selective associations are sufficient for the occurrence of long-delay learning.     

Developmental flavor experience affects utilization of odor, not taste in toxiphobic conditioning

Feeding experiences were varied in developing rats and the effects upon flavor neophobia and lithium chloride-induced flavor aversions were observed. In Experiment 1, nursing experience of neonate rats was reduced by artificial feeding via intragastric cannula; the rats then were tested with apple juice paired with lithium chloride injection at weaning or maturity. Conditioned aversions were not affected, but neophobia to novel apple juice was attenuated in artificially-reared rats tested at maturity. In Experiment 2, rats received enriched feeding experience after weaning, which consisted of (a) obtaining many complex flavors, a few of which were paired with poisoning, effortlessly in the home cage, or (b) foraging for various foods on an elevated maze. No dramatic effects on neophobia or conditioned taste aversion for saccharin water were apparent. In Experiment 3, rats were given experience after weaning with vanilla-scented water either paired or unpaired with quinine water, and then tested with the odor of almond or that odor compounded with saccharin water for neophobia and lithium-induced aversions. Flavor-experienced rats exhibited more pronounced odor conditioning and more resistance to extinction of the odor aversion after both simple and compound conditioning. In contrast, saccharin taste aversions were relatively unchanged. Apparently, enriched feeding and drinking experience facilitates the utilization of odor more than taste cues.     

Role of the area postrema in three putative measures of motion sickness in the rat

After thermal cauterization of the area postrema in rats the absence of conditioned taste aversion to sucrose paired with lithium chloride (0.15 M, 3.3 ml/kg) was used as a pharmacologic/behavioral index of area postrema damage. In a subsequent experiment the effects of area postrema lesions on three measures proposed as species-relevant measures of motion sickness were studied, using off-vertical rotation at 150 degrees/s for either 30 or 90 min. Lesions of area postrema did not alter postrotational suppression of drinking or amount of defecation during motion. The initial acquisition of conditioned taste aversion to a novel cider vinegar solution paired with motion was not affected by lesioning of the area postrema, but these taste aversions extinguished more slowly in lesioned rats than in sham-operates or intact controls. Results are discussed in terms of proposed humoral factors which may induce motion sickness and in light of recent data on the role of the area postrema in similar measures in species possessing the complete emetic reflex.     

Flavor aversions produced by contingent drug injection: Relative effectiveness of apomorphine, emetine, and lithium

Shortly after rats began drinking saccharin solution, different groups of them were injected with different doses of apomorphine, emetine, or lithium. A control group was not injected at all. Six days later, the rats were given free access to saccharin solution and to water. Aversions to saccharin solution were obtained in all injected groups and tended to become more pronounced as the dose level increased. At similar dose levels, lithium produced the most pronounced aversions, apomorphine produced the weakest aversions, and emetine was intermediate. A follow-up study with squirrel monkeys confirmed that lithium produces more pronounced aversions than either emetine or apomorphine. From these results, it seems worthwhile to try lithium in the chemical aversion treatment of alcoholism.     

Context-dependent latent inhibition in taste aversion learning

The effects of taste stimulus preexposure, either in the presence or in the absence of a specific contextual cue consisting of a specific noise-producing bottle, upon the conditioning and testing of conditioned taste aversions to the taste (saccharin) plus context (noisy-bottle) compound stimulus were investigated. Four groups of rats were given preexposure trials (latent inhibition) to either: (1) novel saccharin in novel noisy bottles, (2) novel saccharin in familiar silent bottles, (3) familiar water in novel noisy bottles, (4) familiar water in familiar silent bottles, in six trials. During conditioning, saccharin was presented in the noisy bottles followed by lithium chloride for all the groups. At testing, saccharin was presented in the noisy bottles for both one-bottle and two-bottle tests of aversion. It was indicated that the conditioning decrement produced after both saccharin and noisy bottle preexposure was overwhelmingly greater than any produced after preexposure to the elements. These results, discussed in relation to current theories of latent inhibition and perceptual learning, further underline the overwhelming significance of exteroceptive contextual elements in conditioned taste aversions.     

Anorexia and conditioned taste aversions in the rat

The present study examined whether or not certain anorexic agents produced flavor aversions. Rats showed comparable anorexia when injected with lithium chloride, ammonium sulfate, arginine·HCl, and d-glucose. Only lithium chloride produced a flavor aversion to either a novel liquid or food. Only arginine was found to interfere with the formation or recall of an association. The effects of the other chemicals were discussed in terms of the relationship between anorexia and induced sickness.     

Poison-based avoidance learning with flavored or colored water in guinea pigs

Guinea pigs were fed a solution which had a distinctive taste or appearance and one hr later were made sick by an intraperitoneal injection of lithium chloride. Upon recovery from the effects of sickness the animals in Expt 1 showed aversions to a weak tasting, sour solution or to a strong tasting, sweet solution. Animals in Expt 2 formed aversions to tap water which had been colored either red or blue while those in Expt 3 formed aversions to tap water which had been presented in either red or blue drinking tubes. When, however, sickness was not contingent upon drinking a distinctive solution there was no sign of decreased consumption of the test solutions. The differences between the outcome of the Expts 2 and 3 and those typically found with rats can be explained by the fact that guinea pigs appear to use both taste and visual cues in food selection whereas rats primarily use only gustatory cues. Since vision in the guinea pig is no more acute than vision in rats and substantially more limited than vision in other animals who have formed aversions to visual cues, the results of Expts 2 and 3 also suggest that the ability to form poison-based aversions to visual cues is not totally dependent upon a highly developed visual system.     

Associative interference with taste aversions after contextual discrimination learning

In two experiments, rats were first given discriminative training with two distinctive contexts, such that a flavor was paired with lithium chloride (LiCl) in one context, alternating with presentations of the flavor alone in another context. Contextual control of the fluid ingestion was observed in that rats reduced the fluid intake in the LiCl-paired context but drank the solution in the context never paired with lithium. Having learned this discrimination, the rats were now given a second flavor in their home cage before being injected with LiCl and transferred to the previously lithium-paired context. In Experiment 1, the acquisition of an aversion to the novel flavor was blocked when this flavor and the contextual cues are conditioned as a compound. In Experiment 2, the blocking effect and the conditional control over fluid consumption were abolished when the associative strength of the LiCl-paired context had been extinguished by exposing the animals to water in the contexts after discriminative training. These results are interpreted as evidence that context dependency of conditioned taste aversions is mediated by a summative effect of the context–LiCl and flavor–LiCl associations.     

Potentiation of odor by taste in rats: tests of some nonassociative factors

The contribution of nonassociative neophobia and sensitization to the potentiation of odor by taste in rats was tested in three experiments. In Experiment 1, neophobia for almond odor (O), saccharin taste (T), and odor-taste compound (OT) cues was tested before and after noncontingent lithium chloride 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 Experiment 2, 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 Experiment 3, 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. These studies support an associative "indexing" hypothesis of the potentiation effect in rats.     

Rat data which suggest alcoholic beverages should be swallowed during chemical aversion therapy,not just tasted

There were four pretraining procedures: A, in which rats drank sugar water prior to lithium sickness: P. in which sugar water was passed over the tongue prior to lithium sickness: Li, in which no taste experience preceded lithium sickness: NPT. in which the rats were exposed neither to the sugar water nor to lithium sickness. Lithium was then used to produce aversions to some other solution by dividing each of the pretraining groups into four subgroups. The solutions were novel NaCl, novel vinegar, novel alcohol, or familiar alcohol. Regardless of which solution was made aversive. the A pretraining procedure produced the strongest aversions and the Li procedure produced the weakest aversions. In the final phase, the preference for sugar water was tested. The A procedure produced far stronger aversions than the P procedure.     

Effects of novelty and familiarity on illness-induced aversions to food and place cues in coyotes (Canis latrans)

Two experiments investigated the effects of novelty and familiarity on illness-induced aversions to taste and place cues in coyotes (Canis latrans). Coyotes were made ill on familiar food laced with lithium chloride in a novel place and then received preference tests. In Experiment 1, coyotes avoided the previously poisoned familiar food in the novel treatment place but readily ate the same familiar food in a familiar safe place. In Experiment 2, the results of Experiment 1 were replicated, and it was found that coyotes would eat a different familiar food in the novel treatment place. On the basis of the results of this and other studies, a model for averting animals from places where they are not wanted is presented.     

Types of food aversions: animal, vegetable, and texture

Despite a growing body of research investigating the origins and effects of food aversions, few research instruments have been developed to measure aversions to specific types or categories of food. Undergraduates (N = 209) responded to a series of food aversion questionnaires. The results suggest that people tend to be averse to 2 types of foods (vegetables and meats or fats) and to the texture and taste of certain foods (e.g., oysters). Aversions were slightly more prevalent among women than among men and were correlated with lower educational levels. The authors provide a means of advancing future research on this problem by reliably identifying 3 categories of food aversions. Future researchers should evaluate additional food categories and expand the focus on food aversions beyond the current concern with learned avoidance of specific food items.     

Simultaneous odor-taste and taste-taste compounds in poison-avoidance learning

In six experiments, rats received an odor or a taste alone or in simultaneous compound with another taste prior to lithium chloride-induced illness. Aversions to the target odor and the target taste were then assessed. In Experiments 1–3, the presence of the taste in compound with the target during conditioning attenuated the strength of the aversions to both the target odor and the target taste. Although these results were consistent with the familiar principles of compound conditioning, they contradicted previous reports of potentiation, rather than attenuation, of odor conditioning by taste. In Experiment 4, taste again attenuated the conditioning of odor when a second odor was presented during the CS-US interval. In Experiment 5, we looked for odor potentiation with a within-subject design, and in Experiment 6, we examined an alternative method of presenting odor. In neither case did we find odor potentiation by taste. Over the range of conditions investigated here, a taste often attenuates, and never potentiates, the conditioning of aversions to both odors and tastes.     

Types of Food Aversions: Animal,Vegetable, and Texture

Despite a growing body of research investigating the origins and effects of food aversions, few research instruments have been developed to measure aversions to specific types or categories of food. Undergraduates (N = 209) responded to a series of food aversion questionnaires. The results suggest that people tend to be averse to 2 types of foods (vegetables and meats or fats) and to the texture and taste of certain foods (e.g., oysters). Aversions were slightly more prevalent among women than among men and were correlated with lower educational levels. The authors provide a means of advancing future research on this problem by reliably identifying 3 categories of food aversions. Future researchers should evaluate additional food categories and expand the focus on food aversions beyond the current concern with learned avoidance of specific food items.     

Relationship between vomiting and taste aversion learning in the ferret: studies with ionizing radiation, lithium chloride, and amphetamine.

The relationship between emesis and taste aversion learning was studied in ferrets (Mustela putorius furo) following exposure to ionizing radiation (50-200 cGy) or injection of lithium chloride (1.5-3.0 mEq/kg, ip). When 10% sucrose or 0.1% saccharin was used as the conditioned stimulus, neither unconditioned stimulus produced a taste aversion, even when vomiting was produced by the stimulus (Experiments 1 and 2). When a canned cat food was used as the conditioned stimulus, lithium chloride, but not ionizing radiation, produced a taste aversion (Experiment 3). Lithium chloride was effective in producing a conditioned taste aversion when administration of the toxin was delayed by up to 90 min following the ingestion of the canned cat food, indicating that the ferrets are capable of showing long-delay learning (Experiment 4). Experiment 5 examined the capacity of amphetamine, which is a qualitatively different stimulus than lithium chloride or ionizing radiation, to produce taste aversion learning in rats and cats as well as in ferrets. Injection of amphetamine (3 mg/kg, ip) produced a taste aversion in rats and cats but not in ferrets which required a higher dose (> 5 mg/kg). The results of these experiments are interpreted as indicating that, at least for the ferret, there is no necessary relationship between toxin-induced illness and the acquisition of a CTA and that gastrointestinal distress is not a sufficient condition for CTA learning.     

Amount of training and cue-evoked taste-reactivity responding in reinforcer devaluation

In two experiments, rats received minimal (16) pairings of one auditory conditioned stimulus (CS) cue with a sucrose reinforcer, and extensive (112) pairings of another auditory CS with that reinforcer. After sucrose was devalued by pairing it with lithium chloride in some rats (Devalue groups) but not others (Maintain groups), taste reactivity (TR) and other responses to unflavored water were assessed in the presence of the auditory CSs alone. The minimally trained CS controlled substantially more evaluative TR responses than the extensively trained CS. Those TR responses were hedonic (positive) in the Maintain groups, but aversive (negative) in the Devalue groups. By contrast, food cup entry and other responses thought not to reflect evaluative taste processing were controlled more by the extensively trained cue. These responses were reduced by sucrose devaluation comparably, regardless of the amount of training. The results suggest rapid changes in the content of learning as conditioning proceeds. Early in training, CSs may be capable of activating preevaluative processing of an absent food reinforcer that includes information about its palatability, but that capability is lost as training proceeds.     

Taste familiarity and apomorphine-induced taste aversions in humans

Human volunteers learned taste aversions to a relatively novel cranberry flavor paired with apomorphine-induced illness. These aversions were significantly reduced by pretreatment familiarization to the flavor unless an unpalatable interfering flavor was introduced just prior to the administration of apomorphine. The outcomes have implications for taste-aversion learning in humans and for the control of flavor preferences in patients undergoing illness-inducing chemotherapy.