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Research using short musical sequences and musical tracks created by means of computer algorithms has demonstrated that individuals with or without musical skills can match these soundtracks to specific tastes with above-chance accuracy. More recently, a study that investigated implicit effects associated with crossmodal congruency/incongruency between auditory cues and food images found that such soundtracks are effective in eliciting facilitating effects of taste quality classification with congruent food images as well. In the present study, we tested whether this crossmodal congruency between auditory cues and food images may also influence food image choice by means of a forced-choice task. We selected and used sweet and salty soundtracks as stimuli and food images including both low- and high-calorie exemplars and asked participants to select which food they would prefer to eat (one sweet and one salty) while listening to the soundtracks. We found a general greater proportion of food choices in the soundtracks matching tastes conditions, and that soundtracks matching tastes are effective in influencing congruent food image choices, supporting previous research and adding new interesting outcomes.

Music has been associated with taste and shown to influence the dining experience. We asked whether sound that is associated with taste affects taste perception of food. In two studies (study 1: N = 20, 13 women; study 2: N = 20, 17 women), participants evaluated the taste of cinder toffee while listening to either of two soundscapes associated with sweet and bitter taste, respectively, or no sound. In study 1, participants rated the taste on a visual-analog scale (VAS) anchored with "bitter" and "sweet", aiming to replicate a previous study (Crisinel et al., ). In contrast, four separate scales were used in study 2 to report the extent of bitter, sweet, sour, and salty taste to test whether taste qualities were influenced by sound differentially. Additionally, taste intensity and pleasantness were rated in both studies. Taste intensity was increased in the presence of a sound, while pleasantness was not affected. In study 1, sound shifted bitter-sweet ratings in the direction of the congruent sound, i.e. samples tasted sweeter with "sweet" sound and more bitter with "bitter" sound, replicating Crisinel et al.'s () results. However, this effect was abolished when a "no-sound" control was included in the statistical model. Taste ratings in study 2 showed no effect of sound on any specific taste quality, suggesting that the influence of sound on taste in study 1 reflects an artifact of the scale rather than an actual shift in perception. Together, the data provide evidence for taste-sound correspondences without effects on taste-quality specific perception.

When participants eat foods, they direct their attention to the particular taste quality that is the target of evaluation and subsequently perceive the intensity of the attended taste quality. We defined the ease with which participants pay attention to a particular taste quality as the “noticeability” of that quality. In our previous study, Japanese participants evaluated noticeability and intensity of five fundamental taste qualities (sweetness, umami, saltiness, sourness, and bitterness) under open- and closed-nostril conditions, using a popular traditional Japanese confection, yokan. The correlation between noticeability and intensity of sweetness was significantly reduced when participants were tested with open nostrils. Therefore, we hypothesized that high familiarity with a food and its olfactory information is necessary to decrease the correlation between these two scales. In order to verify this hypothesis, we asked Japanese and German participants, who have different food cultures, to subjectively evaluate yokan, which is familiar to Japanese but unfamiliar to Germans. In a control condition, marshmallows were used which are familiar to all participants. Participants consumed each food under open- and closed-nostril conditions and evaluated the noticeability and intensity of the five fundamental taste qualities. There were significant differences between the participants’ groups as the correlation between noticeability and intensity was reduced significantly only for sweetness of a familiar food under open-nostril condition. These results support our hypothesis that high familiarity with a food and its olfactory information might be necessary to decrease the correlation between noticeability and intensity of a particular taste quality. This finding suggests that perception of a food is influenced by its familiarity and retronasal aroma. These results suggest when a food is unfamiliar, the noticeability and intensity of a particular taste quality are not much altered by the retronasal aroma, but when a food is highly familiar, retronasal aroma serves to decouple noticeability and intensity of a given taste quality.

Taste liking influences the way in which people match tastes to shapes. However, taste–shape matching cannot be explained entirely by taste hedonics. Here, we assess whether variations in taste intensity influence such crossmodal correspondences. Participants were presented with five basic tastants in two concentrations and had to rate them on roundness/angularity shape scales, as well as in terms of liking, and intensity. The results revealed that taste quality, intensity, and participants’ liking of the taste significantly predicted the roundness/angularity of the tastants. The results also revealed a positive correlation between perceived intensity and roundness/angularity for each of the tastants except sweet, and a negative correlation between liking and roundness/angularity for all of the tastes. These results are discussed in terms of the mechanism(s) that underlie the crossmodal correspondence between taste and shape.

The intensity of sucrose (its perceived concentration) and its palatability (positive hedonic valence associated with ingestion) are two taste attributes that increase its attractiveness and overconsumption. Although both sensory attributes covary, in that increases in sucrose concentration leads to similar increases in its palatability, this covariation does not imply that they are part of the same process or whether they represent separate processes. Both these possibilities are considered in the literature. For this reason, we tested whether sucrose’s perceived intensity could be separated from its hedonically positive palatability. To address this issue, rats were trained in a sucrose intensity task to report the perceived intensity of a range of sucrose concentrations before and after its palatability was changed using a conditioned taste aversion (CTA) protocol. We found that the subjects’ performance remained essentially unchanged, although its palatability was changed from hedonically positive to negative. Overall, these data demonstrate that sucrose’s perceived intensity and its positive palatability can be dissociated, meaning that changes of one taste attribute render the other mostly unaffected. Thus, the intensity attribute is sufficient to inform the perceptual judgments of sucrose’s concentrations.

Ageing affects taste perception as shown in psychophysical studies, however, underlying structural and functional mechanisms of these changes are still largely unknown. To investigate the neurobiology of age-related differences associated with processing of basic tastes, we measured brain activation (i.e. fMRI-BOLD activity) during tasting of four increasing concentrations of sweet, sour, salty, and bitter tastes in young (average 23 years of age) and older (average 65 years of age) adults. The current study highlighted age-related differences in taste perception at the different higher order brain areas of the taste pathway. We found that the taste information delivered to the brain in young and older adults was not different, as illustrated by the absence of age effects in NTS and VPM activity. Our results indicate that multisensory integration changes with age; older adults showed less brain activation to integrate both taste and somatosensory information. Furthermore, older adults directed less attention to the taste stimulus; therefore attention had to be reallocated by the older individuals in order to perceive the tastes. In addition, we considered that the observed age-related differences in brain activation between taste concentrations in the amygdala reflect its involvement in processing both concentration and pleasantness of taste. Finally, we state the importance of homeostatic mechanisms in understanding the taste quality specificity in age related differences in taste perception. (C) 2015 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY-NC-ND license.

The Food Neophobia Scale (FNS) measures reluctance to try novel foods. In describing foods, the term complexity is not well defined. The objective of this work was to assess the acceptability of familiar and novel foods, with varying levels of flavor complexity in both salty and sweet foods, by food neophobics and neophilics and to assess the effect of expectation (frame-of-reference effect) and familiarity on the acceptability of foods. FNS was administered to 864 subjects, who were classified to neophobic, or neophilic based on their FNS scores. Experiment 1, which was replicated twice, focused on four familiar foods, prepared in two versions, an original version and a more flavorful version. Subjects rated foods on complexity, acceptability and expectation. Neophilics gave significantly higher acceptability ratings to complex foods than bland foods and vice versa for neophobics. The different versions of foods did not always meet panelists’ flavor expectations. Experiment 2 included eight commercial foods, four salty and four sweet, with two novel and two familiar foods used within each taste category/quality. One of the foods within the familiar or novel pairs was expected to be flavorful (e.g. chili is typically served as spicy) and the other expected to be bland. Subjects rated foods on complexity, acceptability, familiarity and expectation. Six out of the eight flavorful versions of foods were chosen by subjects as more complex. Significant factors were taste quality, novelty, expectation, and familiarity (p

Sucralose avoiding rats detect a bitter-like taste quality in concentrations of sucralose that are strongly preferred over water by sucralose preferring rats. Here, we investigated whether sucralose preferrers (SP) also detect a bitter-like quality in sucralose that may be masked by an increased perception of sucralose's sweet-like quality. A microstructural analysis of sucralose intake revealed that, at concentrations they avoided in preference tests, sucralose avoiders (SA) consumed smaller and fewer bouts of sucralose than SP. Interestingly, the concentration-dependent increase in sucralose preference in SP was not associated with larger bouts or increased lick rate, two measures that are expected to increase with increasing perceived sweetness. This suggests that SP can detect an aversive quality in sucralose, but this perception of a presumably bitter-like quality may be masked by increased salience of a sweet-like quality that sustains high levels of intake in SP. Further evidence for increased sweet-taste perception in SP, relative to SA, was obtained in a second study in which SP consumed more of a palatable sweet-milk diet than SA. These are the first data to suggest that SP are not blind to the bitter-like quality in sucralose, and that there may be differences in sweet-taste perception between SP and SA.

Taste is considered as one of the five traditional senses and has the ability to detect the flavour of food and certain minerals. Information of taste is transferred to the cortical gustatory area for identification and discrimination of taste quality. Animals have memory recognition power to maintain the familiar foods which are already encountered. Animal shows neophobic response when it encounters novel taste and shows no hesitation when the food is known to be safe. Palatability is the hedonic reward provided by foods and fluids. Palatability is closely related to neurochemicals, and this chemical influences the consumption of food and fluid. Even though, the food is palatable that can become aversive and avoided as a consequence of postingestional unpleasant experience such as malaise. This review presents the overall view on brain mechanisms of taste, flavour and palatability.

Both physiological and imaging approaches have led to often-disparate conclusions about the organization of taste information in gustatory cortex (GC). In this study, we used neuroanatomical and imaging approaches to delineate the likely area of insular cortex given to gustatory function and to characterize taste responses within this delineated area in female and male C57BL/6J mice. Anterograde tracers were injected into the taste thalamus (the medial parvicellular portion of the ventral posterior medial division, VPMpc) of mice and the thalamic terminal field was investigated across the cortex. Working within the delineated area, we used two-photon imaging to measure basic taste responses in >780 neurons in layer 2/3 located just posterior to the middle cerebral artery. A nonbiased, hierarchical cluster analysis revealed multiple clusters of cells responding best to either individual or combinations of taste stimuli. Taste quality was represented in the activity of taste-responsive cells; however, there was no apparent spatial organization of primary taste qualities in this region.SIGNIFICANCE STATEMENT Recent studies investigating taste coding within the gustatory cortex have reported highly segregated, taste-specific regions containing only narrowly tuned cells responding to a single taste separated by large non-taste-coding areas. However, focusing on the center of this area, we found a large number of taste responsive cells ranging from narrowly to broadly responsive with no apparent local spatial organization. Further, population analysis reveals that activity in the neuronal population in this area appears to be related to measures of taste quality or hedonics.

Many persons misidentify the quality of taste stimuli, a phenomenon termed “taste confusion.” In this study of 1000 persons, we examined the influences of age, sex, causes of chemosensory disturbances, and genetically determined phenylthiocarbamide (PTC) taster status on taste quality confusions for four tastants (sucrose, citric acid, sodium chloride, caffeine). Overall, sour-bitter confusions were most common (19.3%), followed by bitter-sour (11.4%), salty-bitter (7.3%), salty-sour (7.0%), bitter-salty (3.5%), bitter-sweet (3.4), and sour-salty (2.4%) confusions. Confusions for sweet were

SUMMARYInformational cues such as the price of a wine can trigger expectations about its taste quality and thereby modulate the sensory experience on a reported and neural level. Yet it is unclear how the brain translates such expectations into sensory pleasantness. We used multilevel mediation analysis of neural and behavioral data obtained in participants who tasted identical wines cued with different prices. We found that the brain's valuation system (BVS) in concert with the anterior prefrontal cortex explained the effect of price cues on taste pleasantness ratings. The sensitivity of the BVS to rewards outside the taste domain moderated the strength of these effects. Moreover, brain mediators of price cue effects overlapped with brain regions previously found to be involved in placebo analgesia. These findings provide novel evidence for the fundamental role that neural pathways linked to motivation and affective regulation play for the effect of informational cues on sensory experiences.

The primary taste cortex is located in the insula. However, exactly where in the insula the human primary taste cortex is located remains a controversial issue. Human neuroimaging studies have shown prominent variation concerning the location of taste-responsive activation within the insula. A standard protocol for gustatory testing in neuroimaging studies has not been developed, which might underlie such variations. In order to localize the primary taste cortex in an fMRI experiment, we used a taste delivery system to suppress non-taste stimuli and psychological effects. Then, we compared brain response to taste solution during a passive tasting task condition and a taste quality identification task condition to verify whether this cognitive task affected the location of taste-responsive activation within the insula. To examine which part of insula is the primary taste area, we performed dynamic causal modeling (DCM) to verify the neural network of the taste coding-related region and random-effects Bayesian model selection (BMS) at the family level to reveal the optimal input region. Passive tasting resulted in activation of the right middle insula (MI), and the most favorable model selected by DCM analysis showed that taste effect directly influenced the MI. Additionally, BMS results at the family level suggested that the taste inputs entered into the MI. Taken together, our results suggest that the human primary taste cortex is located in the MI.

Much of the research exploring the relationship between taste quality and affective state suggests that sweet-tasting foods are associated with pleasant feelings, and sour- and spicy-tasting foods are associated with unpleasant feelings. The findings of arousal response as a component of overall affective state are less clear with respect to taste quality. The present study investigated the relationship between taste quality and affective state by comparing arousal and pleasantness ratings of neutral images from the International Affective Picture System (IAPS). Participants (N = 55) recorded these ratings during consumption of sprays which varied in taste quality (sweet, sour, or spicy). As hypothesized, sweet sprays elicited significantly higher ratings of pleasantness than sour or spicy sprays ( η 2 p = .14) on the neutral images. However, arousal ratings did not differ among the three taste quality conditions. Implications of the findings in a broader framework and suggestions for future research are discussed.

Pfaffmann, famous for pioneering work in taste neurophysiology, was a great supporter of psychophysics. He wrote: “Indeed it can be said that without behavioral study, hand in hand with physiological and anatomical methods, one gets only a partial insight: telling where, and to some degree how, but not for what!” [The Psychologists, 1974; Chem Senses Flavour 1 (1974) 61]. The psychophysical studies he initially encouraged concerned mechanism (e.g. taste quality coding), but later methodological advances permitted valid comparisons of taste sensations across groups. Quantification of genetic as well as pathological variation permits the demonstration of links between oral sensory variation, food preferences, diet and health.

Over the past 25 years, there have been two opposing views of how taste information is represented in the activity of gustatory neurons. One view, the across-fiber pattern (AFP) theory, postulates that taste quality is represented by the pattern of activity across the afferent population. Stimuli with similar tastes produce similar patterns of activity. The other view is that activity in a few distinct neuron types codes taste quality in a "labeled-line" fashion. Neurons responding best to sucrose, for example, would represent "sweetness," and those responding best to NaCl would code "saltiness." Some of these neuron types appear to have a biological significance, such as the NaCl-best cells, which receive input about sodium stimuli exclusively from an amiloride-sensitive epithelial ion channel. However, the relatively broad tuning of these neurons makes it unlikely that they are capable of unambiguously coding information about taste quality. Rather, these neuron types play a critical role in establishing unique AFPs that distinguish among taste stimuli. The relative activity across these cell types represent taste quality, much like the patterns of activity across broadly tuned photoreceptors code information about stimulus wavelength.

The nontoxic and nonshock Morrison operant technique was used to evaluate taste quality in rat and marmoset: response to a tastant test solution in pursuit of a pellet reward was dependent on making a choice between two bars that had been linked in discrimination training to qualitatively different stimulus pairs (NaCl versus either HCl, QHCl, or NH(4)Cl). The percentage distribution of bar-press responses to test stimuli showed: (1) stability of quality across 0.069-0.3 M NaCl, 0.003-0.1 M HCl, and 0.0001-0.003 M QHCl; (2) for LiCl, a quality change consistent with human reports of a "sour" to "salty" shift; (3) a suggestion that the "salty-like" quality of NH(4)Cl and NaCl are not perceptually equivalent; (4) NaNO(3) shares NaCl-like, QHCl-like, and NH(4)Cl-like components; (5) CaCl(2), KCl, and MgCl(2) share QHCl-like and NH(4)Cl-like components; and (6) responses to HCl and QHCl were not hedonically driven in the rat. Comparison of rank order correlations of single-unit firing rates to the distribution of bar-press responses for the same test stimulus concentration revealed that (7) no single level of the gustatory pathway exclusively accounts for the operant response distribution pattern to either simple or complex tastants, and (8) discriminations between tastants, one of which may be qualitatively complex, are not necessarily mediated only at levels proximal to the solitary nucleus. Thus, the Morrison discrimination technique effectively yields statements about gustatory quality without use of negative reinforcers and largely uninfluenced by tastant hedonics.

A novel delivery method is described that incorporates taste stimuli into edible strips for determining n-propylthiouracil (PROP) taster status. Edible strips that contained 400 or 600 nanomoles of PROP were prepared for psychophysical studies. Using these strips, we measured taste intensity, taste hedonics, and taste quality responses in a sample of healthy volunteers (n = 118). Participants were also asked to assess a single NaCl strip, a quinine strip, 3 NaCl solutions, and 3 PROP solutions. All psychophysical data were subsequently analyzed as a function of TAS2R38 genotype. The use of PROP strips for distinguishing between individuals with at least 1 PAV allele and individuals with other genotypes was assessed and compared with the use of PROP solutions for making this same distinction. For the 2 PROP strips and PROP solutions, individuals who expressed at least 1 PAV allele could perceive the bitter taste of PROP. Individuals who expressed 2 AVI alleles responded similarly to 400 nanomole PROP strips and blank strips. Furthermore, individuals with 2 AVI alleles responded to 0.032 and 0.32 mM PROP solutions at intensities that were similar to water, though intensity ratings to 3.2 mM PROP solution exceeded water. In general, those with at least 1 PAV allele rated the bitter taste of PROP as unpleasant in both delivery methods (strips or solutions). Psychophysical data from PROP strips and solutions were consistent with TAS2R38 genotype. These results support the validity of edible taste strips as a method for assessing PROP taste perception in humans.

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 over-estimated. 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.

Manipulating stimulus spacing, stimulus frequency, or stimulus range usually affects intensity judgments. In six experiments, I investigated the locus of analogues of these contextual effects in a "difference" estimation task. When all stimuli elicited the same taste quality, stimulus distribution affected the scale values only when water was included in the stimulus set (Experiments 1-3). When the subjective ranges of two taste qualities were manipulated, different scale values were obtained for the separate qualities in the two conditions (Experiment 4). Manipulation of the expected response distribution did not affect the scale values or the responses (Experiments 5-6). It is concluded that shifts in stimulus distributions or stimulus ranges result in shifts in subjective scale values. The contextual effects can be interpreted as relative shifts of a number of gustatory continua, with water lying on a separate continuum. Proposed is a model for context-dependent judgments, consisting of four stages: stimulus classification, stimulus placement, continuum placement, and continuum projection.

Consumer research has demonstrated halo effects arising from advertising claims on food packaging (e.g., "organic," "no cholesterol") that promote misperceiving products more positively on other dimensions (e.g., low-calorie, low-fat). However, little research has explored the conditions under which such claims might give rise to more negative rather than positive evaluations. This paper highlights two domains of judgment in which an ethical or values-based claim ("organic") can promote negative impressions. In Study 1, participants judged organic foods relative to conventional foods on healthfulness and expected taste quality. Results suggest that whereas organics are perceived as more healthful than conventional foods (consistent with previous findings), they are also perceived as less tasty, especially among participants low in environmental concern. In Study 2, participants judged the effectiveness of a formula drink intended to help alleviate malnourishment that was described as organic or not, depending on experimental condition. Results showed that participants high in environmental concern (who typically evaluate organic products positively) judged the drink more negatively (i.e., as less effective) when it was described as "organic." Discussion focuses on possible mechanisms for these effects, as well as the moderating role of judgment type and perceivers' values in halo effects more broadly.

The effect of colour conditioning on taste, quality and liking perception of fruit flavoured drinks was investigated in this study using a Between-Subjects Experimental Design. This study utilized twenty four (24) psychology students of Covenant University as participants. The colour of the fruit drink served as the independent variable while dependent variables such as taste, quality and liking perception were measured. Six research hypotheses were stated and tested. The results indicated that there was no significant difference in the association of colour with taste based on gender (t =. 29, p>0.05). Colour was observed to have a significant effect on taste and quality perception (t=2.10, p three dependent variables were observed. There was a negative but not significant relationship between colour and taste perception as well as colour and liking perception, while a positive but not significant relationship was observed between colour and quality perception. A significant positive relationship between quality and liking perception was observed (r=.63, p drink. It is therefore recommended that food designers put into consideration the colour of food products as it would have an effect on consumers. decision making and buying behaviour.

We examined the issues of when, and how, consumers' prior beliefs or “theories” might bias their judgments of the association between price and quality using a task that involved taste testing orange juices. When the task was manipulated so that subjects had difficulty in comparing and contrasting the taste quality of the juices, their covariation judgments tended to be theory driven: while these judgments were somewhat sensitive to the actual price-quality relationship in the “data,” they were biased by individuals' prior beliefs about the covariation. Follow-up studies indicated that this effect was not due to an encoding bias in that subjects' prior beliefs about price and quality did not significantly distort their taste perceptions per se. Instead, when subjects found it difficult to discriminate among the stimuli with regard to taste quality, they appeared to have formed their covariation judgments by making heuristic use of their prior beliefs. Implications are discussed for the covariation judgment process and consumer learning.

Taste detection performance for representatives of the four taste qualities as a function of stimulus volume ( 5 × 10 −4 to 1 × 1 −1 ml) was examined in rats using high-precision gustometry, computer-controlled operant procedures, nonparametric signal detection measures of sensitivity and responsivity, and blind control procedures. The overall sensitivity index was positively related to stimulus volume ( r s = .60 ), with optimal detection performance attained with a 5 × 10 −3 ml stimulus volume for salt tastants and a 1 × 10 −2 ml stimulus volume for the other taste qualities. The overall responsivity index was inversely related to stimulus volume ( r s = − .47 ), especially for sour and bitter tastants. These results are consistent with prior observations and demonstrate that operant methods using small tastant samples produce sensitive estimates of the rat's taste detection performance and response bias.

Recent studies have shown that people can localize a punctate gustatory stimulus on the lingual epithelium in the absence of discriminative tactile cues. The present studies examined the human ability to localize taste sensations on the tongue and to use this information to remove selectively a target stimulus (a flavored, 1 cm(3) gelatin cube) from the mouth when presented with non-target distractors that vary in number and taste. Findings indicate that humans are capable of localizing and removing either an aversive or an appetitive gustatory target from a field of tactile distractors via taste sensations alone, although this ability diminishes as the number of distractors increases (implicating serial searches, rather than parallel). In addition, humans can localize and selectively remove a target taste in the presence of distractors of another distinct taste quality. Under these conditions performance is either unaffected or reduced, which indicates that contrast with the distinct taste of the distractors does not enhance performance. Humans also are capable of removing a nearly tasteless cube from a field of flavored distractors, but this is clearly a more difficult task, suggesting that 'tactile capture' of taste occurs for the tasteless target cube and interferes with the localization of taste. Finally, perceived suprathreshold stimulus intensity did not seem to be related to the ability to localize and remove a target stimulus via taste sensations and failed to account for variations in performance across individuals.

The pleasant sensory qualities of the traditionalWestern cuisine derives mainly from animal fat,whereas traditional Japanese cuisine contains lessfat and relies more on “dashi” (Japanese broth) toenhance food palatability. At the beginning of the20th century, Dr. Kikunae Ikeda noticed that anunidentified taste quality, distinct from the four ba-sic tastes (sweetness, saltiness, sourness and bitter-ness), was present in palatable foods. He found thistaste most clearly in soups rich in “dashi” preparedfrom Japanese sea tangle (

In peripheral taste the coding mechanism remains an enigma. Among coding theories the "across-fiber pattern" argues that activity across fibers codes for taste, whereas the "labeled line" claims that activity in a particular set of fibers underlies a taste quality. We showed previously that chimpanzee chorda tympani taste fibers grouped according to human taste qualities into an S-cluster, responding predominantly to sweet stimuli, a Q-cluster, sensitive to bitter tastants, and an N-cluster, stimulated by salts. The analysis showed that information in the S-line suffices to distinguish stimuli of one taste quality from the others. However, one condition for the labeled line remained: that blockage of activity in a particular line must cause blockage of one taste quality, but of no other, or its onset give rise to the sensation of a taste quality. Here we studied this requirement with gymnemic acids and miraculin. In humans and chimpanzees, gymnemic acids suppress the sweet taste of all sweeteners whereas miraculin adds a sweet taste quality to sour stimuli. Gymnemic acids also abolish miraculin-induced sweet taste. We found that gymnemic acids practically abolished the response to every sweetener in the chimpanzee S-cluster. Equally important, they had no effect on the responses of the Q- and N-clusters. After miraculin, the S-cluster fibers responded to acids as well as to sweeteners, although they had not responded to acids before miraculin. Gymnemic acids abolished this miraculin-induced response to acids and responses to sweeteners in the S-fibers. These results link the sweet taste quality to activity in fibers of the S-cluster. Thus the S-cluster fibers satisfy the definition of the labeled-line theory: "that activity in a particular fiber type represents a specific taste quality."

The breadth of responsiveness of rat taste cells to the four basic taste stimuli was studied using the entropy measure (H) proposed by Smith and Travers. H values range from 0.0 for narrow tuning to 1.0 for broad tuning. Based on the responses of depolarizing receptor potentials of 26 rat taste cells to the four basic taste stimuli, taste cells were classified into nine NaCl-best, four Q-HCl (quinine-HCl)-best, 10 HCl-best and three sucrose-best cells. NaCl-best cells were narrowly tuned to the four basic taste stimuli, but the other three stimuli-best cells were broadly tuned to the stimuli. In all, 85% of the taste cells responded to more than one of four basic taste stimuli. The mean H values for NaCl-best, Q-HCl-best, HCl-best and sucrose-best cells were 0.285, 0.832, 0.781 and 0.796 respectively. The mean H value for all 26 taste cells was 0.621. This was larger than H in rat gustatory fibers. Transformation of large H values in taste cells into small H values in taste fibers may be due to a non-random interaction between taste cells and taste fibers during the synaptic formation. Broad tuning properties of rat taste cells suggest that the across-taste cell response pattern may play an important role in taste quality coding mechanisms.

The present study demonstrated that 100 microM amiloride serves as an ineffective conditioned taste stimulus in a taste aversion paradigm. Even if amiloride has a detectable taste, it's unlikely that its behavioral effects in salt mixture experiments are due to its inherent taste quality.

The flavor of a food can be defined as the combination of its taste, smell, chemical irritation (the common chemical sense), and temperature. In this chapter, the contribution of taste and smell will be discussed. In the first sections, basic anatomy and physiology of the chemical senses will be described. Some indication of the rapid strides in understanding reception and transduction will also be provided. Much of this information has recently been reviewed in detail by Brand and Shah (1992). Leaning heavily on this review, in the beginning of this chapter an overview of this rapidly advancing area will be provided. In subsequent sections the psychological aspects of the chemical senses, with particular emphasis on the basis for preference and aversions will be concentrated upon. In the final section issues related to specific appetites for salt and protein and to mixtures will be dealt with briefly.

Two of the five fundamental human senses, recognized since antiquity, are chemical senses and three are physical senses. Taste, smell, and the common chemical sense are caused by chemical substances. Sight, sound, and touch are caused by physical forces (light waves, pressure waves, and physical pressure, respectively).

The responses of 84 taste neurons to stimulation of the oral cavity in rats were examined; most taste neurons were found in either a granular insular area (area GI; n = 55) or dysgranular insular area (DI; n = 25), and the others (n = 4) were in an agranular insular area (area AI). The fraction of neurons responding to only one of the four basic stimuli was significantly larger in area GI than in area DI. When neurons were classified by the stimulus which most excited the neuron among the four basic stimuli, every “best-stimulus category” of neurons was found in both GI and DI areas. Quinine-best and “multistimulus-type” neurons, whose responses to some non-best stimulus exceeded 90% of the maximum, were more numerous in the cortex than in the thalamocortical relay neurons. When responses were plotted against taste stimuli arranged in the order of sucrose, NaCl, HCl, and quinine along the abscissa (taste coordinate), response profiles of taste neurons often showed two peaks. The double-peaked type of response profiles were found in every best-stimulus category of neurons in both areas; though, a significantly large fraction of quinine-best neurons in area GI were of the double-peaked type. Some taste neurons in area GI (n = 21) and in area DI (n = 7) were inhibited by one to two taste stimuli, particularly by the stimuli present next to the best one along the taste coordinate. In correlation profiles — correlation coefficients between sucrose and NaCl and between HCl and quinine — pairs of stimuli which were located next to each other on the taste coordinate were significantly smaller in area GI than in area DI. It is thus highly probable that area GI plays an important role in fine taste discrimination and area DI in integration of taste information.

Nine women diagnosed as having primary anorexia nervosa (ANs), five women diagnosed as having bulimia (Bs), and seven normal control women (NCs) were tested for perception of taste quality and intensity using the method of magnitude estimation. The four taste stimuli used were sucrose, hydrochloric acid (HCI), sodium chloride (NaCl), and quinine hydrochloride (QHCI). Four different log molar concentrations of each of these four taste stimuli were employed. No significant differences were found among the three groups in ability to identify taste quality. However, there were significant differences (p

Taste quality responses elicited by chemical, electrical, and tactile stimulation of 40 single fungiform papillae in four subjects were examined. A comparison of responses revealed differences in taste quality mediation for the three different classes of stimuli. Chemical stimulation elicited multiple taste qualities from a greater proportion of papillae than did either electrical or tactile stimulation. In addition, the chemical data revealed the presence of consistent bitter-sour and sour-salty confusions. Both tactile and electrical stimulation elicited relatively few bitter and sweet responses, as compared with either sour or salty responses. However, correct quality identification in these papillae for bitter and sweet compounds was no different from that for sour or salty compounds. In addition, electrical stimulation elicited a greater proportion of salty responses than did tactile stimulation. Comparison of the taste quality elicited by either tactile or electrical stimulation of a papilla with the taste quality exhibiting the greatest relative chemical sensitivity in the papilla also revealed independence of responding, and it was observed that both electrical and tactile stimulation elicited consistent taste quality responses from papillae in which these taste qualities could not be elicited by any concentration of any chemical test compound. The observed differences in quality judgments are discussed as possibly being the result of cross-modal gustatory associations resulting from nongustatory components of inadequate stimulation.

Facial expressions of 23 neonates were analyzed for specific features following oral stimulation with distilled water, 0.1 and 1.0 M sucrose, 0.15 and 0.25 M urea, and 0.0001 M quinine hydrochloride. Responses were videotaped and later decoded in a double-blind setting. While some features were present for all stimulations, other components were consistently associated with a specific taste quality. Within a quality, increasing the concentration elevated the incidence of features associated with that quality. Estimates of magnitude and hedonic tone conveyed by the total facial response to each stimulus suggested that the face was, within limits, an accurate reflection of stimulus quality and intensity.

Description d'un protocole permettant de mesurer le temps de detection, de differenciation et d'identification d'un melange sapide lors de l'analyse sensorielle, et analyse de l'influence des correlations entre constituants du melange

Etude systematique de la duree de reaction a differents stimuli sapides (sale, acide, complexes) a differentes concentrations, et terminologie utilisee par les membres du jury pour la description du gout percu. Exemples d'applications a des solutions de NaCl, de saccharine, de glutamate et d'acide citrique

As an extension of the analysis of magnitude of response to gustatory stimuli in the parabrachial nuclei5, this study sought to determine to what extent time course of neural response coded information about taste quality. A principal components analysis and stepwise discriminant analysis were used to evaluate stimulus-related differences in time course of response. Temporal patterns of response over an 8.192 s period to the 4 basic types of taste stimuli were discriminated from one another at about twice chance level. The discrimination of different qualities of taste by time course exceeded discrimination of different intensities of the stimuli. Analysis of time course restricted to the first 2,048 s of response again revealed significant overall differentiation of the stimuli, but only NaCl and sucrose were individually discriminated. Temporally coded information about gustatory stimuli, particularly in terms of onset characteristics of response, appeared inadequate for perceptual differentiation of taste quality. Such coding might, however, complement an across-neuron spatial pattern code for taste quality in simplifying the decoding of taste input for control of reflexive responses that entail a more inclusive classification of taste stimuli.

In Phase 1 three groups of rats had access to both 32% and 4%, only 32%, or only 4% sucrose solutions. In Phase 2 the first group received only 32%, the other groups remained as before; in Phase 3 all groups were shifted to 4% after a 1- or 10-day interval. In Phase 1 Group 32-4 showed both positive and negative contrast. In Phase 3 successive negative contrast occurred in both retention intervals, but was smaller after the 10-day interval. Following the 10-day interval (but not the 1-day interval), the group with differential experience in Phase 1 (Group 32-4) showed larger contrast than did Group 32-32. Results are discussed in terms of factors determining generalization and memory.

Rats were given three-choice preference tests involving saccharin, NaCl, and citric acid. One substance was familiar to S, a second was novel, and a third (CS) has been associated with gastrointestinal illness. Conditioned aversions were acquired and retained when the CS was saccharin or NaCl but not when it was citric acid. In a second experiment, using a simpler two-choice test, a conditioned taste aversion to citric acid again could not be detected. Together, the results suggest that CS adequacy may vary as function of taste quality.

Early psychophysical studies of human taste papillae, using chemical stimuli, indicated that single papillae often have a broad taste quality range. Recent investigations, using both chemical and electrical stimulation, have contested this result; single papillae were observed to mediate only one of the so-called primary taste sensations (salty, sweet, bitter or sour). In each case the techniques used were such as to leave the conclusion open to doubt. The present study, employing an improved technique for chemical stimulation, corroborates the wide sensitivity range shown in the earlier studies. This result is in accord with the available anatomical and electrophysiological data. Moreover, it concurs with similar findings from all sensory modalities in support of the hypothesis that sensory receptors and afferent neurons typically have broad quality ranges, regardless of the characteristics of the phenomenal organizations derived from the information coded in this manner.

SummaryFeeding is dynamically regulated by the palatability of the food source and the physiological needs of the animal. How consumption is controlled by external sensory cues and internal metabolic state remains under intense investigation. Here, we identify four GABAergic interneurons in the Drosophila brain that establish a central feeding threshold which is required to inhibit consumption. Inactivation of these cells results in indiscriminate and excessive intake of all compounds, independent of taste quality or nutritional state. Conversely, acute activation of these neurons suppresses consumption of water and nutrients. The output from these neurons is required to gate activity in motor neurons that control meal initiation and consumption. Thus, our study reveals a layer of inhibitory control in feeding circuits that is required to suppress a latent state of unrestricted and nonselective consumption.

In the natural environment, sweetness can nearly always be equated with energy. Consequently its detection is associated with a powerful hedonic appeal which declines only as energy needs are met. In this chapter we will first describe the sensory code by which sweet stimuli are represented and then discuss the neural basis of the hedonic response to sweetness and its malleability by physiological need.

Visceral feedback after eating a meal modifies the taste of the food and drink by psychological processes which are of special interest to students of biofeedback. For simplicity, consider an unlimited amount of a tasty fluid placed before a hungry subject. The taste of the fluid is the perceptual signal, ingestion is the process to be controlled and homeostatic well-being is the state to be achieved. If the fluid is a creamy substance, rich in calories, it tastes delicious at the beginning of the meal and the subject drinks heartily. As the caloric mass accumulates in the gut, satiety is achieved before tissue needs are redressed, as if the viscera has sensing devices which accurately estimate the amount of food needed to achieve the ultimate homeostatic balance (Novin, 1976; Schachter, 1971; McHugh, Moran, & Barton, 1975).

Reaction times (RTs) to four groups of substances that provoke different taste qualities were measured. Measurements for all substances with the same taste, equalized in perceived intensity and provoking a very strong taste, were made concurrently for each subject. The comparisons were made on the individual level. No significant differences in RTs to substances with the same taste quality were found. When the factor of perceived intensity is kept constant, no effect of the stimulus chemical composition on RTs seems to be present. RTs to stimuli with different tastes differ significantly, the shortest being to salt and the longest to bitter. The difference in RTs for sour and sweet substances is small, and the subjects were not all alike in terms of the order of RTs with respect to these stimuli.