The Temporal Automated System for Taste Experiments (TASTE)

We describe a new, open flow device for presenting taste stimuli to human subjects under controlled conditions of timing. The device delivers each stimulus as a mist to the participant’s tongue through one of 16 nozzles attached to a linear slide. Software controls the position of the slide, the duration of the stimulus, and the duration of the pre- and poststimulus water rinses and records the responses of the participant. Temporal characteristics of this system make it especially applicable to studies on the role of attention in taste perception.     

Godot: A real-time data acquisition and control program for the PET microcomputer

This article discusses a program for the PET microcomputer that is used to record the amount of time a human infant spends attending to one of two stimuli presented via 35-mm slides and a slide projector. The program records the number of attention episodes for either stimulus, the duration of slide presentation, and the number of slides presented. Also controlled are the transfer of data onto cassette tape at the end of the session, the detection of buttonpresses from an external keyboard, and the changing of stimuli. The interfacing used in the system and specialized subroutines are also described.     

Human motor responses to simultaneous aversive stimulation and failure on a valued task

The effects of presentation of an aversive stimulus and simultaneous failure on a bogus intelligence test upon a subject's aggressive reactions were studied. The subject's fist clenching was used as an indicator of aggression. Four conditions, generated by the combinations of two kinds of stimulus delivered to the subjects (aversive or nonaversive) and two outcomes of the task (failure or success), were investigated. 20 female and 20 male students (ages: 17-34 years) were instructed, upon the reception of an aversive or nonaversive acoustic signal, to press with the right hand a device that displayed a slide. Each slide presented an item from an intelligence test, to which the subjects were either allowed to answer successfully (success) or not (failure). Failure increased the subject's autonomic arousal, as measured by photoplethysmographic sensors, in all stimulation conditions, but only the condition with aversive stimulation increased the speed of clenching. This was interpreted as indicating subject's tendencies to aggression. These results are discussed in relation to the effects of frustration.     

Cross-enhancement of the sour taste on single human taste papillae

The subjective intensity of one taste quality can be increased by prior exposure of the tongue to a different taste quality stimulus. This phenomenon, called cross-enhancement, may be the result of interactions among the physiological mechanisms that code taste quality. Another possible explanation is that the water solvent of the second stimulus acquires a taste after exposure of the tongue to the first stimulus. This water taste could add to the taste of the solute in the second stimulus and result in an increase of its subjective intensity. A third possibility is that taste receptors on the tongue may be sensitized by exposure to a taste stimulus. Using a small number of highly trained subjects, we have demonstrated that sucrose can enhance the intensity of an acid taste on the single papilla. Neither water taste nor sweet taste system activation played any role in the mediation of this enhancement. Through a series of experimentally derived inferential steps, we conclude that this phenomenon depends on the removal of protons from the acid receptors. In addition, we have demonstrated in the single papilla, that suppression of the acid taste when in mixture with sucrose can occur without sweet system activity. We conclude that sugars, through their capacity to bind protons, act to reduce the availability of protons to the acid receptors.     

Age-dependent facilitation of taste-footshock conditioning by prior exposure to the training context

Among adult rats, gustatory stimuli are easily associated with illness, but not with external unconditioned stimuli such as footshock. Recent evidence indicates, however, that this cue-to-consequence specificity may vary ontongenetically. The present studies examined the acquisition of an aversion to a taste paired with footshock in 5- and 15-day-old rats. Consistent with previous reports, 5-day-old rats avoided the taste that preceded footshock, while 15-day-old subjects did not express an aversion to the taste paired with footshock. Exposure to the training context for either 1 or 5 h prior to conditioning disrupted taste-footshock conditioning in the 5-day-old subjects. For the 15-day-old subjects, 1 h of pre-conditioning exposure to the training context had no effect on conditioning, whereas a longer duration of preexposure promoted conditioning to the taste cue. The results suggest ontogenetic differences in stimulus selection.     

The Influence of Prior Handling on the Effective CS-US Interval in Long-Trace Taste-Aversion Conditioning in Rats

The Psychological Record - In conditioned taste aversion (CTA), a taste, the conditioned stimulus (CS), is paired with an illness-inducing stimulus, the unconditioned stimulus (US), to produce...     

Determinants of cumulative successive contrast in saltiness intensity judgments

When all stimuli elicit the same taste quality, solutions preceded by a high concentration level are judged to be significantly less intense than solutions preceded by a low concentration level. After repetitious stimulation with a different tasting stimulus, the intensity of the present stimulus is overestimated. This phenomenon is called “successive contrast.” In the present study, the cumulative effects of three identical stimuli on the saltiness ratings for a test stimulus are investigated. The preceding stimuli are manipulated with regard to taste quality, saltiness intensity, total taste intensity, and complexity. Whether the size of the cumulative contrast effect is associated with the degree of dissimilarity between preceding stimuli and test stimulus, or with the saltiness or total taste intensity of the preceding stimuli, is investigated. The size of the contrast effect depends on the type of preceding stimulus, its intensity, and the type of test stimulus. No association was found with judgments of the degree of dissimilarity between the preceding stimuli and the test stimulus. For nonsalty preceding stimuli, the contrast effects are independent of concentration level. When the preceding stimuli taste at least partly salty, the total intensity appears to determine the size of the contrast for an unmixed salty test stimulus.     

Weanling and senescent rats process simultaneously presented odor and taste differently than young adults

Weanling, young-adult, and senescent Wistar albino rats had a novel odor/taste stimulus or a single taste stimulus either paired or explicitly unpaired with the unconditioned stimulus, lithium chloride. Animals were then given a saccharin vs water preference test. Standard preference scores indicated that the odor competed with taste for association with the US in young-adult rats but potentiated the conditioned aversion to taste in weanling and senescent rats. Results were interpreted in terms of age-related attentional differences which were hypothesized to account for infantile amnesia and for the memory dysfunction typically observed in senescent animals.     

Effect of response task on taste adaptation

Two experiments studied whether subjects reported complete adaptation of a taste sensation. Three tasks were chosen based on their use in other laboratories: hand lowering to connote stimulus absence, magnitude estimation, and cross-adaptation of a brief stimulus following a prolonged stimulus. In the first experiment, different groups of 9 subjects received the three different tasks; in the second experiment, all 20 subjects received all three tasks. In both experiments, subjects failed to demonstrate complete taste adaptation in at least 50% of adaptation trials. Response task did affect the likelihood of observing complete taste adaptation.     

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.     

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.     

A random-pulse generator with adjustable pulse duration

An electronic device for generating random pulses of adjustable duration within a minimal and maximal interval boundary is described. The instrument is useful in electro- and psychophysiological research where randomization of stimulus input is required.     

Intragastric copper sulfate produces a more reliable conditioned taste aversion in vagotomized rats than in intact rats

Although copper sulfate is an emetic stimulus, preliminary experiments failed to obtain a taste aversion in intact rats following intragastric administration as had been previously reported in the literature. Several experiments were therefore run to further investigate the capacity of intragastric copper sulfate to function as an unconditioned stimulus for taste aversion learning and the role of the vagus in mediating that learning. The results of the first series of experiments showed that intragastric administration of copper sulfate (5 mg/kg X 5H2O) was more effective in reliably producing a taste aversion in vagotomized rats than in sham-operated control rats. The second experiment examined the effects of area postrema lesions on the acquisition of a taste aversion produced by intragastrically administered copper sulfate in vagotomized rats. The results indicated that the taste aversion observed following treatment with intragastric copper sulfate in vagotomized rats could be prevented by lesions of the area postrema. The present results indicate that intragastric administration of copper sulfate is a more reliable unconditioned stimulus for taste aversion learning in vagotomized rats than in intact rats. It is not certain what factors might account for the discrepant results between the present experiments and previously published research.     

A confusion matrix for the study of taste perception

Taste stimulus identification was studied in order to more thoroughly examine human taste perception. Ten replicates of an array of 10 taste stimuli--NaCl, KCl, Na glutamate, quinine. HCl, citric acid, sucrose, aspartame, and NaCl-sucrose, acid-sucrose, and quinine-sucrose mixtures--were presented to normal subjects for identification from a list of corresponding stimulus names. Because perceptually similar substances are confused in identification tasks, the result was a taste confusion matrix. Consistency of identification for the 10 stimuli (T10) and for each stimulus pair (T2) was quantified with measures derived from information theory. Forty-two untrained subjects made an average of 57.4% correct identifications. An average T10 of 2.25 of the maximum 3.32 bits and an average T2 of 0.84 of a maximum 1.0 bit of information were transmitted. In a second experiment, 40 trained subjects performed better than 20 untrained subjects. The results suggested that the identification procedure may best be used to assess taste function following 1-2 training replicates. The patterns of taste confusion indicate that the 10 stimuli resemble one another to varying extents, yet each can be considered perceptually unique.     

Intensity-volume interaction effects in gustatory perception

Three paired comparison type experiments, with 20 different Ss in each, using citric acid at three concentration levels as taste stimulus, investigated some effects of differences in stimulus liquid bulk on perceived relative taste intensity, and effects of concentration differences on perceived relative volume. Perceived relative taste intensity increases slightly with increasing liquid bulk and relative perceived bulk increases slightly with concentration, both effects being significant: p < .01. An explanation in terms of a taste-quantity constancy mechanism is advanced.     

Taste potentiation of auditory aversions in rats (Rattus norvegicus): a case for spatial contiguity

An aversion for an auditory stimulus was established in laboratory rats when a tone was spatially and temporally contiguous with a novel taste in a food conditioned stimulus compound followed by toxicosis. The procedure involved varying the location of the tone relative to a novel tasting food. During toxicosis conditioning, one group ate sweet food with a speaker located in the food, two groups ate sweet food with the speaker displaced (near or far) from the food, and a fourth group was presented with a tone without food available. It was found that the potentiation of auditory aversions required both the presence of a novel taste and spatial contiguity between the taste and the tone.     

Does taste or odor activate the same brain networks after retrieval of taste potentiated odor aversion?

When simultaneous presentation of odor and taste cues precedes illness, rats acquire robust aversion to both conditioned stimuli. Such a phenomenon referred to as taste-potentiated odor aversion (TPOA) requires information processing from two sensory modalities. Whether similar or different brain networks are activated when TPOA memory is retrieved by either the odor or the taste presentation remains an unsolved question. By means of Fos mapping, we investigated the neuronal substrate underlying TPOA retrieval elicited by either the odor or the taste conditioned stimulus. Whatever the sensory modality used to reactivate TPOA memory, a significant change in Fos expression was observed in the hippocampus, the basolateral nucleus of amygdala and the medial and the orbito-frontal cortices. Moreover, only the odor presentation elicited a significantly higher Fos immunoreactivity in the piriform cortex, the entorhinal cortex and the insular cortex. Lastly, according to the stimulus tested to induce TPOA retrieval, the BLA was differentially activated and a higher Fos expression was induced by the odor than by the taste in this nucleus. The present study indicates that even if they share some brain regions, the cerebral patterns induced by either the odor or the taste are different. Data are discussed in view of the relevance of each conditioned stimulus to reactivate TPOA memory and of the involvement of the different labeled brain areas in information processing and TPOA retrieval.     

Precise positioning of tachistoscopic stimuli with Scientific Prototype slide changers

An easily made device for eliminating horizontal movement of stimuli in Scientific Prototype slide changers is described. This device does not permanently alter the tachistoscope and does not interfere with normal operation of the slide changer.     

A computer-controlled electrogustometer for the estimation of evoked taste thresholds

Reliable taste detection thresholds in humans are difficult to obtain for either research or clinical purposes because ordinary taste stimuli cannot be generated and presented by means of a computer. However, in investigations of taste dysfunction, electrical taste stimulation (electrogustometry) is sometimes employed. Minute anodal direct currents are applied manually to the tongue, giving rise to an acid taste experience through the liberation of protons into the saliva. This experience accords with recent findings on the mechanisms underlying sour taste perception. The device described here is a safe and accurate constant-current device, operating under computer control at very low amperages, making it possible to apply modern psychophysical procedures to the measurement of evoked taste thresholds.     

Augmentation, not blocking, in an A+/AX+ flavor-conditioning procedure

An A+/AX+ Pavlovian conditioning design typically produces weakened or blocked conditioning to stimulus X. Two experiments were conducted in which rats first received an odor (A+) paired with an emetic US, and then received odor and taste (AX+) paired with the US. In both experiments, the preconditioned odorfacilitated conditioning to the taste. In Experiment 1, a group that received two odor-illness pairings in A+ conditioning had a stronger taste aversion than a group that only had a single odor-illness pairing. Experiment 2 demonstrated that the strengthened taste aversion in the A+/AX+ condition was not due to stimulus generalization. The results represent a unique outcome in the flavor-aversion literature that is similar to potentiation. We propose that this facilitated conditioning to X in the A+/AX+ design be termedaugmentation.