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Psychophysical testing of taste and flavour reactivity in young patients undergoing treatment with removable orthodontic appliances.

Upper removable appliances (URA), as well as full dentures, are known to be the cause of various complaints related to oral handling of food and beverages, phonation and vocalization, in addition to general discomfort. To test the hypothesis that taste and flavour perception might also be affected by URA, 22 young orthodontic patients (10 males and 12 females aged 11.5 +/- 1.7 years; experimental group) wearing URA and 17 subjects (seven males and 10 females aged 11.6 +/- 2.0 years; control group) not wearing any orthodontic appliances were presented with a battery of eight intra-oral gustatory and three retro-nasal flavour stimuli. The subjects in the experimental group were tested on three different occasions and those in the control group on two occasions. All participants were required to label verbally the perceived taste and flavour sensations, as well as to estimate the palatability and intensity of the perceived sensation on a 100 mm visual analogue scale (VAS). Means and standard deviations were calculated from the individual values and then compared between the two groups and among the different testing times. Statistical significance was assessed with a level of confidence set at 0.025. The results revealed no significant difference between the indicative values chosen to represent taste and flavour reactivity, neither between the groups nor among different dates of testing within each group. Orthodontists should therefore encourage patients to also use the URA during meals, without any detrimental effect on taste and/or flavour perception.

Case-Control Studies↗

Food recognition by the elderly.

While blindfolded, 27 young college students and 29 elderly subjects tasted and smelled a series of unseasoned blended foods. The elderly subjects were significantly less able to identify the foods than young subjects. The elderly subjects rated the foods on adjective scales in such a way that a multidimensional scaling of these ratings yielded only one dimension, related to the hedonic aspect of the foods. The multidimensional solution for youthful subjects' ratings was two-dimensional, indicating more discrimination among foods for young subjects compared with the elderly. Significantly more elderly subjects commented on the weakness of the smell or taste of the foods.

Adolescent↗

Cognitive and chemosensory influences on age-related changes in the ability to identify blended foods.

Two experiments explored the effects of age, sex, and chemosensory function on the ability of blindfolded participants to identify a series of 12 blended foods. In the first experiment 40 persons aged 18 to 26 and 40 persons over 65 years of age attempted to identify the pureed foods using both taste and odor cues. Half the participants in each group were female, half were male. The average percentage correct on first attempt to identify was significantly higher in young than in old individuals. An Age X Sex interaction revealed a female superiority over men in the elderly group only. With feedback and practice, participants improved, but the age effect remained significant. In the second experiment, 20 young and 17 elderly women who had their nostrils occluded attempted the same identification task. When deprived of olfaction, the performance of young women fell to the same level as that of the old women on first exposure. The relative contributions of cognitive, gustatory, and olfactory/trigeminal factors to the age-related decline in chemosensory function are discussed.

Adolescent↗

Taste intensity perception in aging.

Men (n = 91) and women (n = 79) between the ages of 23 and 88 years made cross-modal matches of distance to the perceived intensity of aqueous solutions representing the four basic taste qualities. Traditional analysis, which characterizes age-group performance in terms of the slope of a group's psychophysical function, yielded results consistent with previous findings in that some flattening of slope was observed in the oldest group. Analyses based on the slope of the functions generated by individual participants demonstrated significant regression on age for some qualities. None of these findings were observed in the analogous analysis of variance (ANOVA). Significant age-related changes in Intraclass Correlation Coefficient (ICC) were demonstrated by both ANOVA and regression analysis. The ICC reflects the consistency of an individual's discriminative response over repeated stimulus presentations. Its variation with age was dependent upon taste quality.

Adult↗

Age and biochemical status predict preference for casein hydrolysate.

Two studies investigated relationships between chemosensory preference, age, and biochemical status. In the first study, 10 young and 16 elderly participants rated the relative pleasantness of several concentrations of casein hydrolysate, a nutritionally significant stimulus, prepared in an amino acid deficient soup base. Blood assays were performed to assess total protein, albumin, and blood urea nitrogen (BUN). Elderly persons and those whose blood values indicated lower biochemical status preferred higher concentrations than young persons and those with blood values indicative of higher biochemical status. In a second study 20 young and 20 elderly participants performed the same pleasantness task and then rated the stimuli for intensity using the method of magnitude matching. For each person a single index of biochemical status was produced using measures of protein, albumin, and BUN. As in the first study, age and biochemical index predicted preferred concentration of casein hydrolysate, but intensity ratings did not.

Adult↗

Oral sensory changes in aging.

Perception of oral sensory intensity was assessed in healthy, community-dwelling men (n = 46) and women (n = 41) between 25 and 93 years of age. Cross-modal matches of distance to perceived intensity were obtained for five types of oral stimuli (sugar water, salt water, heated or chilled water, water thickened with methylcellulose, and local pressure on the dorsal tongue). Differences among stimulus types were observed for measures of response size (mean, median, maximum, and range of response distance and rate of increase with stimulus strength), but not measures of judgment quality, repeatability (ICC), and conformity to a linear rise with stimulus strength (r2). Age had no significant effect on any of the response measures for any stimulus type except pressure. All measures of response to lingual pressure except median size declined significantly with age. We conclude that (a) the various oral stimulus types elicit perceptions that differ in intensity but were judged with similar accuracy, and that (b) aging brings a specific decline in the perception of localized lingual pressure while both size and accuracy of intensity judgments are maintained for the other oral sensitivities tested.

Adult↗

Long-term zinc deficiency decreases taste sensitivity in rats.

The effects of zinc deficiency on taste sensitivity were examined in rats by recording the electrophysiological responses of the chorda tympani (CT) nerve and by use of a preference test. Male 4-wk-old Sprague-Dawley rats were given free access to a diet containing 2.2 (zinc-deficient), 4.1 (low zinc) or 33.7 (zinc-sufficient) mg zinc/kg diet. A fourth group was pair-fed the zinc-sufficient diet (with respect to the zinc-deficient rats). A two-bottle preference test using 0.15 mol/L NaCl and water revealed that NaCl preference was greater in the zinc-deficient and low zinc groups than in the control groups (zinc-sufficient and pair-fed) after 4 d of feeding. In the case of quinine hydrochloride solution (0.01 mmol/L), the preference was greater in zinc-deficient rats than in the other groups after 9 d, and the low zinc rats never showed a preference. Electrophysiological recording indicated that in the zinc-deficient rats, the CT nerve response to 0.20 mol/L NaCl was significantly less than that in the control rats after 21 d of feeding. In the low zinc rats, this response was significantly less than in the control rats after 35 d. The responses to quinine hydrochloride (0.02 mol/L), L-glutamic acid, HCl (0.01 mol/L) and NH(4)Cl (0.25 mol/L) in the zinc-deficient rats were not significantly reduced until d 42. These findings suggest that long-term zinc deficiency decreases taste sensitivity at the level of the CT nerve and that the change in NaCl preference due to zinc deficiency occurs before any change in NaCl taste sensitivity.

Animal Nutritional Physiological Phenomena↗

Gustatory disturbance due to cerebrovascular disorder.

OBJECTIVES: Review three cases of unilateral gustatory disturbance due to central lesions caused by cerebrovascular disorders, describe clinical findings and the results of taste examinations, and discuss the central gustatory pathways in humans. STUDY DESIGN: Retrospective review of three gustatory disturbance cases due to cerebrovascular disorders. Additional review of 12 cases with central gustatory disturbance that have been reported. METHODS: Central lesions of three cases were examined by magnetic resonance imaging or computed tomography scan. Electrogustometry and a filter paper disk assay using taste solutions were performed in these cases for each of the bilateral gustatory nerves. RESULTS: In one case of pontine infarct, gustatory disturbance ipsilateral to the lesion was found, and in one case of thalamic infarct and one case of internal capsular infarct, gustatory disturbance contralateral to the lesion was observed. CONCLUSIONS: Fifteen cases of unilateral gustatory disturbance due to central lesions, including the present cases, have been reported to our knowledge. Examination of these cases strongly suggested that the central gustatory pathways in humans ascend ipsilaterally from the solitary nucleus of medulla oblongata to the pons, and from the pons, cross to a higher position in midbrain and reach the thalamus contralaterally.

Adult↗

Further characterization of the quinine taste discrimination stimulus in rhesus monkeys: effects of inter-trial interval, number and distribution of test stimuli.

The purpose of the current investigation was to characterize further the taste discriminative stimulus properties of quinine. Using a food-maintained two-choice (quinine and water) discrimination paradigm, the effects of varying inter-trial intervals, and the number and distribution of test stimuli were examined in rhesus monkeys (Macaca mulatta). Monkeys were trained to respond under a chain schedule of reinforcement (FR5B-fluid, FR30B-food) with a 60-s inter-trial interval. Interestingly, the quinine discrimination remained invariant across all the conditions tested: alterations in inter-trial interval (0, 15, 30, 45, 60 s), alterations in the number of test stimuli (six at quarter-log unit increments [0.1-1 mg/ml] versus 10 at quarter-log unit increments [0.01-1 mg/ml]), and alterations in the distribution of the test stimuli (quarter-log unit increments [0.1-0.1 mg/ml] versus half-log unit increments [0.01-1 mg/ml]) failed to alter the quinine discriminative stimulus (ED50s ranged from 0.18-0.29 mg/ml). Furthermore, incorrect lever selections were very rare (less than 12% of all test sessions), independent of test stimuli order (i.e. quinine followed by water trials, water followed by quinine trials), and independent of the progress through the test session (i.e. incorrect lever selections were consistent--approximately one error for every 10 trials--within early, middle and late portions of the session). These results demonstrate the reliability and robustness of the quinine taste discriminative stimulus in rhesus monkeys and provide further validation for the experimental paradigm.

Animals↗

Contact endoscopic comparison of morphology of human fungiform papillae of healthy subjects and patients with transected chorda tympani nerve.

BACKGROUND: The chorda tympani nerve (CTN) carries gustatory fibers from taste buds of fungiform papillae (fPap) of the anterior portion of the tongue. Accordingly, middle ear surgery with transection of the CTN may result in gustatory impairment. With use of contact endoscopy, the present study aimed to compare number and shape of fPap and subepithelial vessel formation in patients after CTN transection with that of healthy controls. MATERIAL AND METHODS: The number of fPap per square centimeter was obtained in addition to measures of gustatory sensitivity using electrogustometry and intensity ratings of natural taste stimuli. Data from 32 healthy subjects (mean age 40 yr; 16 female, 16 male) were compared with those from 14 patients whose CTN had been cut and partly resected during middle ear surgery because of cholesteatoma (mean age 38 yr; 7 female, 7 male). Middle ear surgery was performed by two of the authors. RESULTS: In healthy subjects, a higher fPap density was found on the tongue's tip compared with its edge; younger subjects had higher densities than older subjects. No sex-related differences were observed. Patients with transected CTN exhibited a significant decrease of taste function as measured with both natural and electric stimuli. In patients, we found significantly fewer and flatter fPap on the side of the tongue where surgery had been performed in comparison with the contralateral side. In addition, fPap density at the ipsilateral side was significantly lower compared with fPap density on the respective side in healthy controls. CONCLUSION: As established through contact endoscopy, the number of fPap decreases in relation to deafferentation and also in relation to the subjects' age, both of which are accompanied by a decreased gustatory sensitivity.

Adolescent↗

Loss of taste in the elderly: sex differences.

The sensation of taste was tested in 280 normal people of all ages and both sexes. The sensitivity for the basic tastes decreased with increasing age, but more in men than in women; there was no sex difference in people under the age of 40. The different smoking habits of men and women did not explain this finding. It is suggested that there is a sex-specific decrease in the taste sensitivity with aging.

Adolescent↗

Blood pressure, salt taste and sodium excretion in rats exposed prenatally to high salt diet.

Blood pressure, sodium excretion and salt taste were examined in Sprague Dawley (SD) and Munich Wistar (MW) rats exposed prenatally to either a high salt (2.3% NaCl w/w) or control diet. There was no significant difference in blood pressure at 2, 6 or 12 months between high salt and control groups in either strain. Similarly there was no significant difference in sodium excretion following a saline load by gavage (150 mmol/l, 1.5% BW). Munich Wistar rats which received high salt diet prenatally exhibited a reduced saline preference when offered a choice between water and 150 mmol/l NaCl as drinking fluid. There was no significant difference in saline preference between Sprague Dawley rats which received the high salt or control diet. Prenatal exposure to high salt diet failed to alter the blood pressure or excretion of a salt load in either SD or MW rats. In MW rats but not SD high salt diet prenatally resulted in a reduced saline preference at 3 months of age.

Animals↗

Electrophysiological and behavioural characterization of gustatory responses to antennal 'bitter' taste in honeybees.

We combined behavioural and electrophysiological experiments to study whether bitter taste is perceived at the antennal level in honeybees, Apis mellifera. Our behavioural studies showed that neither quinine nor salicin delivered at one antenna at different concentrations induced a retraction of the proboscis once it was extended in response to 1 M sucrose solution delivered to the opposite antenna. Bees that extended massively their proboscis to 1 M sucrose responded only partially when stimulated with a mixture of 1 M sucrose and 100 mM quinine. The mixture of 1 m sucrose and 100 mM salicin had no such suppressive effect. No behavioural suppression was found for mixtures of salt solution and either bitter substance. Electrophysiological recordings of taste sensillae at the antennal tip revealed sensillae that responded specifically either to sucrose or salt solutions, but none responded to the bitter substances quinine and salicin at the different concentrations tested. The electrophysiological responses of sensillae to 15 mM sucrose solution were inhibited by a mixture of 15 mM sucrose and 0.1 mM quinine, but not by a mixture of 15 mM sucrose and 0.1 mM salicin. The responses of sensillae to 50 mM NaCl were reduced by a mixture of 50 mm NaCl and 1 mM quinine but not by a mixture of 50 mM NaCl and 1 mM salicin. We concluded that no receptor cells for the bitter substances tested, exist at the level of the antennal tip of the honeybee and that antennal bitter taste is not represented as a separate perceptual quality.

Action Potentials↗

Consumption of sweet, salty, sour, and bitter solutions by selectively bred alcohol-preferring and alcohol-nonpreferring lines of rats.

To determine whether selective breeding for high or low oral ethanol consumption is associated with different preferences for nonpharmacological solutions with various flavors, the oral intake of a range of concentrations of sucrose (0.5-64.0 g/100 ml), NaCl (0.025-3.2 g/100 ml), citric acid (0.008-2.048 g/liter), and sucrose octaacetate (0.002-0.512 g/liter) was studied in alcohol-preferring (P) and alcohol-nonpreferring (NP) rats. Separate groups of 7-8 rats from each line were tested for consumption of each of the four flavors. The flavored solutions were presented continuously with water and food always available, and the concentrations were doubled every 48 hr. Although rats from both lines showed a strong preference for the sucrose solutions, P rats consumed greater amounts than NP rats [F(7,98) = 5.57, p < 0.001]. Rats of the P line drank less of the NaCl solutions than NP rats [F(7,98) = 3.88, p < 0.001], but the effect was not as robust as the line differences seen with sucrose. The P and NP rats did not differ in citric acid or sucrose octaacetate intake at any of the concentrations tested. Selective breeding for high oral ethanol preference appears to be positively associated with consumption of sweet solutions and negatively associated with intake of salty solutions.

Alcohol Drinking↗

Taste reactivity in high alcohol drinking and low alcohol drinking rats.

High alcohol drinking (HAD) and low alcohol drinking (LAD) rats were tested, in three exposures, for taste reactivity to five concentrations of alcohol (5%, 10%, 20%, 30%, and 40%, v/v), water, and one concentration each of sucrose and quinine. Of the three reactivity exposures, one was done before a 3-week period of continuous access to water and 10% alcohol, the second test was done immediately after the consumption period, and the final reactivity test was done after 1 month of alcohol abstinence. The results showed that the groups did not differ in reactivity on the initial test. After the consumption tests (when the HAD rats consumed significantly more alcohol than the LAD rats), differences in reactivity were found: HAD rats produced significantly more ingestive responses (which promote consumption) and significantly fewer aversive responses (which facilitate fluid rejection) than LAD rats. These differences were maintained even after 1 month of alcohol abstinence. The present data replicate an earlier experiment with alcohol-preferring (P) rats and alcohol-non-preferring (NP) rats, and indicate that the selective breeding process does not produce differences in the innate perception of the taste of alcohol. However, after experience with drinking alcohol, rats selectively bred for high alcohol consumption exhibit a palatability shift reflected by high ingestive responding and little or no aversive responding. Such a shift would clearly contribute to the maintenance of high levels of alcohol consumption.

Alcohol Drinking↗

Ethanol consumption and taste preferences in C57BL/6ByJ and 129/J mice.

Mice of the C57BL/6ByJ (B6) and 129/J (129) strains were offered different concentrations of taste solutions in 48-hr, two-bottle choice tests. In comparison with the 129 strain, the B6 strain had higher preferences for ethanol, sucrose, and citric acid. They had lower preferences for NaCl and similar preferences for capsaicin and quinine hydrochloride. These data are consistent with the hypothesis that the higher ethanol intake by B6 mice depends, in part, on higher hedonic attractiveness of its sweet taste component.

Alcohol Drinking↗

Preference for higher sugar concentrations and Tridimensional Personality Questionnaire scores in alcoholic and nonalcoholic men.

Animal studies have shown a positive association between the consumption of high concentrations of sweet solutions and subsequent alcohol intake. In a previous clinical study, it was shown that a preference for a high (0.83 M) concentration of sucrose (sweet liking) is characteristic of alcoholics, compared with controls. The present study was designed to determine whether personality variables, reported to be associated with subtypes of alcoholism, differentiate sweet liking alcoholics from sweet liking controls. Fifty-two male controls and 26 alcoholic patients were tested for sweet preference and administered the Tridimensional Personality Questionnaire. Sweet liking alcoholics scored significantly higher on the Tridimensional Personality Questionnaire Novelty Seeking and Harm Avoidance scales and related subscales when compared with sweet liking controls. Further analysis showed that preferred sucrose concentration, Harm Avoidance score, and Novelty Seeking predicted alcoholic versus nonalcoholic group status at 65% sensitivity and 94% specificity, with a correct classification in 85% subjects. We hypothesize that sweet liking may identify a specific alcoholism subtype also characterized by high novelty seeking and high harm avoidance. These findings may have theoretical biological significance and practical clinical implications.

Adult↗