A measure of taste intensity discrimination in the rat through conditioned taste aversions

doi:10.1016/0031-9384(87)90394-5

Physiology & Behavior

Volume 41, Issue 4, 1987, Pages 315-320

https://doi.org/10.1016/0031-9384(87)90394-5 Get rights and content

Abstract

The ability of rats to make intensity discriminations was determined by forming a conditioned taste aversion to a moderate concentration of each of four basic taste stimuli, and then measuring the level of acceptance (number of licks during a 15 sec exposure) shown to a range of concentrations of the same chemical. Rats (N=66) could discriminate between glucose concentrations that were separated by as little as 0.074 M, between NaCl concentrations that differed by 0.029 M, between HCl concentrations that were 9×10⁻⁴ M apart, and between quinine HCl concentrations that differed by as little as 2.4×10⁻⁶ M.

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Cited by (36)

3.08 - Behavioral Analysis of Taste Function in Rodent Models
2020, The Senses: A Comprehensive Reference: Volume 1-7, Second Edition
The purpose of this chapter is to discuss some basic interpretive properties of standard behavioral tasks that have been and can be used to infer the taste capabilities of nonhuman animal subjects and to provide some examples of how several of these paradigms have been successfully applied in efforts to reveal the functional organization of the gustatory system. Specifically, we review the two-bottle preference test, brief access taste testing, operant detection, discrimination, and generalization paradigms, conditioned taste aversion, progressive ratio schedules, and the taste reactivity test and how these procedures have been utilized to study the neural basis of gustation.
Taste, olfactory, and food reward value processing in the brain
2015, Progress in Neurobiology
Citation Excerpt :
Rats with conditioned aversions to 1.0 M glucose show decreasing acceptance of glucose solutions as their concentrations approach 1.0 M. This acceptance gradient can be compared between euglycemic rats and those made hyperglycemic through intravenous injections (Scott and Giza, 1987). Hyperglycemic rats showed greater acceptance at all concentrations from 0.6 to 2.0 M glucose, indicating that they perceived these stimuli to be less intense than did conditioned rats with no glucose load (Giza and Scott, 1987a).
Complementary neuronal recordings in primates, and functional neuroimaging in humans, show that the primary taste cortex in the anterior insula provides separate and combined representations of the taste, temperature, and texture (including fat texture) of food in the mouth independently of hunger and thus of reward value and pleasantness. One synapse on, in a second tier of processing, in the orbitofrontal cortex, these sensory inputs are for some neurons combined by associative learning with olfactory and visual inputs, and these neurons encode food reward value on a continuous scale in that they only respond to food when hungry, and in that activations correlate linearly with subjective pleasantness. Cognitive factors, including word-level descriptions, and selective attention to affective value, modulate the representation of the reward value of taste and olfactory stimuli in the orbitofrontal cortex and a region to which it projects, the anterior cingulate cortex, a tertiary taste cortical area. The food reward representations formed in this way play an important role in the control of appetite, and food intake. Individual differences in these reward representations may contribute to obesity, and there are age-related differences in these value representations that shape the foods that people in different age groups find palatable. In a third tier of processing in medial prefrontal cortex area 10, decisions between stimuli of different reward value are taken, by attractor decision-making networks.
Chronic dietary magnesium-L-threonate speeds extinction and reduces spontaneous recovery of a conditioned taste aversion
2013, Pharmacology Biochemistry and Behavior
Citation Excerpt :
Second, if training is sufficiently extensive and animals are given repeated experiences with 2 gustatory stimuli that are quite similar in taste, they may be able to learn to differentiate between them if one is continued to be reinforced while the other is not. In fact, extremely small differences in concentrations (e.g., 2.4 × 10- 6 M) of the same compound (HCl) can be detected when similar taste discrimination methodologies are employed (Scott and Giza, 1987). In order to interpret our findings as being consistent with MgT-induced enhancement of memory, it is important to confirm that SAC only and SAC + MgT are similar enough so that, in the context of our study, rats were unlikely to detect/recognize subtle taste differences between the 2 stimuli during extinction and our SR test.
Elevation of brain magnesium enhances synaptic plasticity and extinction of conditioned fear memories. This experiment examined the generalizability of this phenomenon by studying the effects of a novel magnesium compound, magnesium-L-threonate (MgT), on conditioned taste aversion (CTA) extinction and spontaneous recovery (SR). Adult male Sprague–Dawley rats were maintained on a 23-hour water deprivation cycle and acquired a CTA following the taste of a CS [0.3% saccharin + 16 mg/ml MgT (SAC + MgT)] paired with a US [81 mg/kg (i.p.) lithium chloride (LiCl)]. Following CTA acquisition, rats drank a water + MgT solution for up to 1 hour/day over the next 31 days. For 14 additional days, some animals continued water + MgT treatment, but others drank water only to allow MgT to be eliminated from the body. We then employed 2 different extinction paradigms: (1) CS-Only (CSO), in which SAC was presented, every-other day, or (2) Explicitly Unpaired (EU), in which both SAC and LiCl were presented, but on alternate days. EU extinction procedures have been shown to speed CTA extinction and reduce spontaneous recovery of the aversion. Throughout extinction, half of the rats in each group continued to drink MgT (now in SAC or supplemental water + MgT solution), whereas the other half drank SAC only/water only until SAC drinking reached ≥ 90% of baseline (asymptotic extinction). Rats receiving MgT just before/during extinction drank less SAC on the first day of extinction suggesting that they had retained a stronger CTA. MgT enhanced the rate of extinction. Furthermore, the MgT-treated rats showed a relatively modest SR of the CTA 30 days later — indicating that the extinction procedure was more effective for these animals. Our data suggest that long-term dietary MgT may enhance the consolidation/retention of a CTA, speed extinction, and inhibit SR of this learned aversion.
Lesions of the central nucleus of the amygdala decrease taste threshold for sodium chloride in rats
2012, Brain Research Bulletin
Citation Excerpt :
The method employed in determining the taste threshold for NaCl solutions involves conditioning animals to avoid a suprathreshold concentration of sodium chloride solution used as a CS. If the conditioned groups are tested with a series of concentrations of sodium chloride, they will avoid the concentrations of NaCl solutions within a certain range identified as the CS (Clarke et al., 2001; du Villard et al., 1981; Ishiwatari and Bachmanov, 2009; Lu et al., 2009a; Ramirez, 1991; Scott and Giza, 1987; Tapper and Halpern, 1968; Yamamoto et al., 1994). Since the approach is based on conditioning a response to a single stimulus concentration and measuring responses to other concentrations, it could strictly be classified as an ‘intensity generalization threshold’ rather than a ‘taste recognition threshold’.
Previous studies reported that NaCl intake was down-regulated in rats with bilateral lesions of the central nucleus of the amygdala (CeA). In line with the evidence from anatomical and physiological studies, such an inhibition could be the result of altered taste threshold for NaCl, one of the important factors in assessing taste functions. To assess the effect of CeA on the taste threshold for NaCl, a conditioned taste aversion (CTA) to a suprathreshold concentration of NaCl (0.1 M) in rats with bilateral lesions of CeA or sham lesions was first established. And then, two-bottle choice tests between water and a series of concentrations of NaCl were conducted. The taste threshold for NaCl is defined as the lowest concentration at which there is a reliable difference scores between conditioned and control subjects. Rats with CeA lesions acquired a taste aversion for 0.1 M NaCl when it was paired with LiCl and still retained the aversion after the two-bottle choice test. The results of the two-bottle choice test showed that the taste threshold for NaCl was 0.0006 M in rats with CeA lesions, whereas in rats with sham lesions the threshold was 0.005 M, which was identical to that of normal rats. The conditioned results confirm the claim that CeA is not essential in the profile of conditioned taste aversion. Our findings demonstrate that lesions of the CeA increased the sensitivity to NaCl taste in rats, indicating that the CeA may be involved in encoding the intensity of salty gustation elicited by NaCl.
Interactions of temperature and taste in conditioned aversions
2010, Physiology and Behavior
Citation Excerpt :
When given a 2-bottle choice between the conditioned thermal cue and a cue of a different temperature, rats would be more motivated to avoid the conditioned cue and consume the “safe” cue, thus demonstrating discrimination. A lack of avoidance under these conditions would more precisely define an inability to discriminate [16,17]. Conversely, generalization behavior can also be shown with a conditioned aversion paradigm.
The influence of temperature on taste cues and the ability to discriminate and learn about different temperatures of foods are important factors regulating ingestion. The goal of this research was to demonstrate that thermal orosensory input can serve as a salient stimulus to guide ingestive behavior in the rat, and also that it interacts with gustatory input during choice and conditioned aversion experiments. A novel apparatus with Peltier refrigerators was used to control the temperature of solutions in 10-min, 2-bottle tests. It was determined that naive rats preferred cold water (10 °C) to warm water (40°). When cold water was paired with a toxic LiCl injection, rats avoided cold water and drank warm water, thus demonstrating that cold water could serve as the conditioned stimulus in a conditioned temperature aversion. Rats conditioned against cold water could discriminate 10 °C water from 16 °C water, but not from 13 °C water, thus showing an ability to discriminate orosensory thermal cues to within 3–6 °C. Rats also generalized conditioned aversions from cold water to cold saccharin and cold sucrose solutions. However, if rats were conditioned against a compound taste and thermal stimulus (10 °C, 0.125% saccharin), the rats could distinguish and avoid each component individually, i.e., by avoiding cold water or warm saccharin. Finally, daily 2-bottle extinction tests were used to assess the strength of aversions conditioned against a taste cue (0.25 M sucrose), a thermal cue (10 °C water), or the combination. Aversions to taste or temperature alone persisted for 7–14 days of extinction testing, but the combined taste–temperature aversion was stronger and did not extinguish after 20 days of extinction testing. These results demonstrate that temperature can serve as a salient cue in conditioned aversions that affect ingestion independent of taste cues or by potentiating taste cues.
Constructing quality profiles for taste compounds in rats: A novel paradigm
2008, Physiology and Behavior
Citation Excerpt :
This refers to the documented tendency of animals to display increased responses to stimuli that have higher intensity than the training stimulus and decreased responses to stimuli that have a lower intensity. Interactions between intensity of the CS and the test stimulus (TS) have been reported to influence the magnitude of avoidance displayed after taste aversion conditioning [11–13]. Finally, given that testing occurs in extinction, the number of test stimuli and test sessions possible is restricted.
We developed a novel behavioral method, adapted from the work by Morrison (1967), for the assessment of taste quality in rats. Four groups of rats were trained to discriminate a standard stimulus (either NaCl, sucrose, quinine, or citric acid, which are widely thought to represent the four basic human taste qualities of salty, sweet, bitter, and sour, respectively) from the remaining three compounds (each at multiple concentrations). Animals were then tested for generalization to the standard stimuli when test compounds were presented and a quality profile was constructed. Rats generalized novel concentrations of standard stimuli completely to their training concentrations and generalized their responses to mixtures of NaCl and sucrose on the basis of the relative concentrations of the stimulus components. In general, the sugars (at high concentrations), denatonium, tartaric acid, and sodium gluconate generalized to sucrose, quinine, citric acid, and NaCl, respectively. Monosodium glutamate generalized to a mixture of sucrose and NaCl. KCl produced a complex generalization profile with notable quinine and citric acid components. Our procedure supplements the current use of the conditioned taste aversion generalization procedure which has some procedural and interpretive limitations. Although our procedure involves the use of a complex stimulus delivery and response measurement apparatus and requires substantial initial conditioning of animals, once trained, a single cohort of animals can be tested for its response to a substantial number of test stimuli over the course of many months without any ostensible loss of stimulus control.

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A measure of taste intensity discrimination in the rat through conditioned taste aversions

Abstract

Behav Biol

Brain Res

Physiol Behav

Brain Res Bull

Electric taste

Stimulus generalization of an illness-induced aversion to different intensities of colored water in japanese quail

Anim Learn Behav

Neural correlates of gustatory intensity and quality

J Neurophysiol

Stimulus intensity dynamism (V) and stimulus generalization

Psychol Rev

Untersuchungen uber die Unterschiedsempfindlichkeit im Bereiche des Geschmacksinns (Studies of sensible discrimination in the gustatory field)

Arch Psychol (Frankf)

The psychological vs. the ethological rat: Two views of the poison avoidance behavior of the rat compared

Anim Learn Behav