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PubMed2005

Influences of aging on taste perception and oral somatic sensation.

BACKGROUND: Many elderly persons report reduced taste perception of the foods they eat. Any disturbance of taste and oral somatic sensations can induce this phenomenon. To determine the cause of decreased taste perception in older persons, the authors investigated age-related changes in taste perception and somatic sensations in the anterior tongue. METHODS: Thirty healthy young and elderly persons participated in this study. Recognition thresholds of four basic tastes (sweet, salty, sour, and bitter) and the threshold of irritating sensation induced by capsaicin were measured by local stimulation using filter-paper disks. Two-point discrimination thresholds were measured to evaluate the spatial acuity of touch sensation. All measurements were carried out at the tip of the dorsal tongue. RESULTS: The recognition thresholds of all four basic tastes of elderly participants were significantly higher than those of young participants. On the contrary, age-associated changes were not observed in 2-point discrimination and capsaicin sensation. CONCLUSIONS: Significant age-associated deterioration was observed in taste but not somatic sensations such as touch and burning pain in the tongue, showing that aging affects taste perception and oral somatic sensations differently. This suggests that decreased taste perception of foods in elderly people may be caused primarily by perceptual loss of taste among oral sensations.

Adolescent↗
PubMed2007

Influence of chronic middle ear diseases on gustatory function: an electrogustometric study.

OBJECTIVE: We aimed to quantitatively determine whether middle ear inflammation associated with unilateral chronic otitis media (COM), cholesteatoma, or otosclerosis affects gustatory function. STUDY DESIGN: Prospective study. SETTING: University Hospital, Department of Otolaryngology. PATIENTS: Forty-two patients had unilateral COM (22 men, 20 women; mean age, 54.2 yr), 57 had unilateral cholesteatoma (35 men, 22 women; mean age, 42.1 yr), and 19 had unilateral otosclerosis (10 men, 9 women; mean age, 49.3 yr). MAIN OUTCOME MEASURES: Patients underwent taste testing using electrogustometry (EGM) and sensation thresholds were compared in the affected and unaffected ears among groups and between affected and unaffected ears in each group. RESULTS: Patients with COM and cholesteatoma exhibited an increase in taste threshold in the affected ears compared to the unaffected ears (p < 0.05), whereas otosclerosis patients did not. The extent of the increase of the sensation thresholds in the affected ears was very similar between patients with COM and those with cholesteatoma (p = 0.548). CONCLUSION: Our EGM study showed that cholesteatoma and chronic middle ear inflammation affected gustatory function to a similar degree.

Adult↗
PubMed1982

Sodium chloride detection threshold in the rat determined using a simple operant taste discrimination task.

A method for training rats to lick at high rates for a water reinforcer after presentation of one tastant and to inhibit or decrease response rate to avoid a time-out, punisher after presentation of another tastant is described and evaluated. The method produced rapid acquisition of simple discrimination and detection tasks, The absolute mean detection threshold for sodium chloride in three rats was 0.0038% (0.0031%-0.0043%. The operant conditioning technique is simple, efficient, and should prove useful for psychophysical and physiological studies of gustation.

Animals↗
PubMed1981

[Psychophysics of sweet taste. II. Statistical theory of the stimulus-response behavior of sweet taste receptors].

Considering various conditions of adaptation, the authors determined the Weber discrimination thresholds for the sweet taste of saccharose. When the adaptation to the basic stimulus is maintained and use is made of the differential coefficient behaviour, the discrimination threshold is an exponential function of the concentration. The discrimination threshold is by definition that amount of stimulant per unit of volume which will produce an effect of the magnitude of 1. Consequently, the numbers of moles being substituted, its reciprocal, the probability of obtaining a stimulus response, is greater than 1. A differential equation, namely (formula: see text), can be formulated as the basis of the stimulus-response behaviour of saccharose, the integration of which yields a discrimination characteristic expressed as (formula: see text). S = concentration of the solution as the stimulus intensity; R = stimulus response expressed in steps. The parameter b is the maximum probability of the stimulus response and can be termed substance-specific concentration coefficient. Rm is the maximum step number when the stimulus intensity tends to infinity; it is also substance-specific. As this characteristic involves both the proportional factors and the differential coefficients, it is called P-D characteristic. From this invariant relationship, the static P characteristic for a very slow increase in stimulus intensity can be derived. When the adaptation to the basic stimulus is abolished by mouth rinsing between tests in paired comparisons, the dependence of the discrimination threshold on the concentration is more than exponential. The stimulus-response characteristics obtained with different time-courses of stimulation are approximated by both the Weber-Fechner and the Stevens law.

Animals↗
PubMed1995

Taste sensitivity and aging: high incidence of decline revealed by repeated threshold measures.

Contrary to what has often been said about the subject, decline in taste sensitivity with aging characterizes virtually everybody and is not the artificial result of averaging large losses of a minority with negligible losses of a majority. This assertion is supported by six repeated measures of sucrose thresholds in each of 15 older (over 64 years) and 15 younger (under 27 years) adult subjects. Threshold was determined by a procedure similar to past studies and with the same results: much scatter and considerable overlap between the thresholds of younger and older subjects. A quite contrasting picture emerges, however, when each subject's six threshold determinations are averaged. Averaging shrinks the individual differences among subjects, as well as the over-lap between younger and older subjects. Although virtually all elderly subjects now revealed taste weakness, reliable individual differences in degree of weakness abound among them, suggesting various individual rates of physiological aging. In contrast, young persons exhibit greater uniformity of sensitivity. These findings were brought out by inter-test correlations, which were much higher for the older subjects; i.e. an older subject who tended to score high (low) on one test tended to score high (low) on the other tests. The study confirms the tenuous nature of brief threshold tests as indices of personal sensitivity as found earlier also in olfactory thresholds and in concurrent measurement of two-point touch thresholds in the present study. This revealed correlated losses between repeated taste and touch thresholds from the same 15 older subjects, unrelated to their exact chronological age.

Adult↗
PubMed1998

Detection of very complex taste mixtures.

Mixtures can often be tasted when all components are too weak to be tasted separately. Such mixtures are said to be integrative. Integration was demonstrated by mixing compounds in concentrations proportional to their separate detection thresholds and then measuring the detection threshold of the mixture as a whole by forced choice with plain water. Mixtures of 3, 6, 12 and 24 compounds were thus evaluated. With earlier data on 2-, 3- and 4-component mixtures, the results show that the concentration of any constituent compound goes down in approximate proportion to the number of compounds with which it is in mixture. This nearly complete integration describes mixtures of like-quality compounds, of unlike-quality compounds, and of both like- and unlike-quality compounds together. Integrative mixtures provide a model for the detection of the ultracomplex stimuli of everyday life, such as foods and drinking waters. Although the degree of integration may trail off slightly with mixtures of high complexity, the results proffer no limit on the number of compounds that can be at least partially integrated. In principle, integration permits detection of natural substances whose myriad components could all be far below threshold. The mechanism of taste integration is speculative, but the facts are congenial to the hypothesis of multiple parallel channels for the processing of intensity and quality.

Food↗
PubMed1982

Cortical substrates of taste aversion learning: dorsal prepiriform (insular) lesions disrupt taste aversion learning.

The functional relation between restricted damage to ventral primary somatosensory neocortex and the ability of rats to acquire conditioned taste aversion (CTA( was examined by a combination of behavioral and neurohistological techniques. Lesions confined exclusively to the established gustatory neocortex (GN) did not disrupt CTA acquisition, nor did lesions confined to suprarhinal cortical areas ventral to the GN. Lesions that encroached on dorsal prepiriform and insular cortices produced CTA acquisition deficits and damaged a large proportion of efferent projections to the prefrontal and precentral neocortex. In a second experiment, lesions of dorsal prepiriform and insular cortices did not modify taste preference-aversion threshold to any of the four taste modalities. It is concluded tha ventral somatosensory neocortical fields, including the established GN, do not mediate CTA acquisition and that rhinal cortices ventral and posterior to the GN are preferentially involved in associative learning for tastes and illness.

Animals↗
PubMed1997

Risk characterization of methyl tertiary butyl ether (MTBE) in tap water.

Methyl tertiary butyl ether (MTBE) can enter surface water and groundwater through wet atmospheric deposition or as a result of fuel leaks and spills. About 30% of the U.S. population lives in areas where MTBE is in regular use. Ninety-five percent of this population is unlikely to be exposed to MTBE in tap water at concentrations exceeding 2 ppb, and most will be exposed to concentrations that are much lower and may be zero. About 5% of this population may be exposed to higher levels of MTBE in tap water, resulting from fuel tank leaks and spills into surface or groundwater used for potable water supplies. This paper describes the concentration ranges found and anticipated in surface and groundwater, and estimates the distribution of doses experienced by humans using water containing MTBE to drink, prepare food, and shower/bathe. The toxic properties (including potency) of MTBE when ingested, inhaled, and in contact with the skin are summarized. Using a range of human toxic potency values derived from animal studies, margins of exposure (MOE) associated with alternative chronic exposure scenarios are estimated to range from 1700 to 140,000. Maximum concentrations of MTBE in tap water anticipated not to cause adverse health effects are determined to range from 700 to 14,000 ppb. The results of this analysis demonstrate that no health risks are likely to be associated with chronic and subchronic human exposures to MTBE in tap water. Although some individuals may be exposed to very high concentrations of MTBE in tap water immediately following a localized spill, these exposures are likely to be brief in duration due to large-scale dilution and rapid volatilization of MTBE, the institution of emergency response and remediation measures to minimize human exposures, and the low taste and odor thresholds of MTBE which ensure that its presence in tap water is readily detected at concentrations well below the threshold for human injury.

Accidents↗
PubMed1988

Olfactory detection and identification performance are dissociated in early Alzheimer's disease.

Ten carefully screened men with very mild symptoms of Alzheimer's disease (AD) and ten healthy controls of similar age were compared on multiple chemosensory tasks: odor detection and identification, and taste detection. The patients scored significantly worse than controls on identification of odors and of a subset of airborne stimuli providing trigeminal stimulation. In contrast, the patients' olfactory detection thresholds as well as taste detection thresholds were not impaired relative to those of controls. The patients' scores on neuropsychological tests and the results 18F-2 deoxy-D-glucose PET studies did not correlate with any of the chemosensory measures. The isolated odor identification deficit suggests that the initial chemosensory impairment in AD is central rather than peripheral.

Aged↗
PubMed1990

Gustatory responses of single neurons in the insula of the macaque monkey.

1. In recordings made from 2,925 single neurons, a region of primary taste cortex was localized to the rostral and dorsal part of the insula of the cynomolgus macaque monkey, Macaca fascicularis. The area is part of the dysgranular field of the insula and is bordered laterally by the frontal opercular taste cortex. 2. The responses of 65 single neurons with gustatory responses were analyzed in awake macaques with the use of the taste stimuli glucose, NaCl, HCl, quinine HCl (QHCl), water, and black currant juice. 3. Intensity-response functions showed that the lowest concentration in the dynamic part of the range conformed well to human thresholds for the basic taste stimuli. 4. A breadth-of-tuning coefficient was calculated for each neuron. This is a metric that can range from 0.0 for a neuron that responds specifically to only one of the four basic taste stimuli to 1.0 for one that responds equally to all four stimuli. The mean coefficient for 65 cells in the taste insula was 0.56. This tuning is sharper than that of neurons in the nucleus of the solitary tract of the monkey, and similar to that of neurons in the primary frontal opercular taste cortex. 5. A cluster analysis showed that at least six different groups of neurons were present. For each of the taste stimuli, glucose, NaCl, HCl, QHCl, water, and black currant juice, there was one group of neurons that responded much more to that tastant than to the other tastants. Other subgroups of these neurons responded to two or more of these tastants, such as glucose and black currant juice, or NaCl and QHCl. 6. On the basis of this and other evidence, it is concluded that the primary insular taste cortex, in common with the primary frontal opercular taste cortex, represents a stage of information processing in the taste system of the primate at which the tuning of neurons has become sharper than that of neurons in the nucleus of the solitary tract, and is moving toward the fineness achieved in the secondary taste cortex in the caudolateral orbitofrontal taste cortex, where motivation-dependence first becomes manifest in the taste system.

Action Potentials↗
PubMed1997

Genetic sensitivity to 6-n-propylthiouracil (PROP) and hedonic responses to bitter and sweet tastes.

Genetically mediated sensitivity to the bitter taste of 6-n-propylthiouracil (PROP) has been associated with greater acuity for bitter and for some sweet tastes. Thus far, few studies have explored the relationship between PROP taste sensitivity and hedonic responses to bitter and sweet. In this study, 87 normal-weight young women were divided into PROP non-tasters (n = 18), regular tasters (n = 49), and supertasters (n = 20), based on their PROP detection thresholds and the scaling of five suprathreshold solutions of PROP and NaCl. Non-tasters had thresholds > 1.8 x 10(-4) mol/l PROP. Supertasters had thresholds < 3.2 x 10(-5) mol/l PROP and PROP/NaCl ratios > 1.70. As expected, dislike of the bitter taste of PROP was determined by its perceived intensity, which was greater among supertasters than among regular tasters or non-tasters. Significant correlations were observed between PROP taste thresholds and the sum of intensity ratings (r = -0.61) and between summed intensity and summed hedonic ratings (r = -0.80). PROP taste sensitivity was weakly linked to enhanced perception of sweet taste, but did not predict hedonic responses to sucrose or to saccharin solutions. Given that the dislike of PROP solutions is determined by their perceived intensity, hedonic responses to PROP solutions may provide a rapid way of screening for PROP taster status.

Factor Analysis, Statistical↗
PubMed1984

Impairment of taste and olfaction in patients with cirrhosis: the role of vitamin A.

Taste and olfaction sensory modalities and the response to vitamin A replenishment were studied in 37 vitamin A deficient patients (determined by low serum levels and abnormal dark adaptation) with stable alcoholic cirrhosis. Among this group of patients, 11 also had low serum zinc levels which ranged from 45 to 63 micrograms/dl. Initial taste and olfaction mean detection thresholds for all test substances were significantly higher (less sensitive) in all patients as compared to 21 sex-matched healthy subjects of the same age range (P less than 0.05). Twenty-seven patients including the 11 patients with low serum zinc were treated with oral vitamin A (10 000 micrograms/d) for 4 weeks. Among the vitamin a deficient patients there was significant improvement following vitamin A treatment in the mean detection and mean recognition thresholds for bitter and salty taste (P less than 0.01) and for pyridine olfaction (P less than 0.05) regardless of zinc status. Improvement in taste and olfaction correlated with a reversal of serum vitamin A levels and dark adaptation toward normal. The mechanism whereby vitamin A affects specific taste and smell (ie salty and bitter taste; pyridine smell) modalities is at present unknown.

Adult↗
PubMed2002

Altered food preference after cortical infarction: Korean style.

BACKGROUND: Altered food preference or preoccupation with certain food after stroke has been rarely described in the literature. METHODS: We report four Korean patients who developed altered food preference secondary to unilateral cortical infarction. RESULTS: Two patients showed preoccupation with meat such as Pulgogi or Kalbi (roast beef flavored with ingredients), which had not been their preference prior to the occurrence of stroke. All the patients became intolerant to the smell and taste of mackerel, and two disfavored hot Kimchi (cabbage salted with hot pepper). Quantitative taste assessment done in the patients revealed decreased taste perception in a variable pattern along with dysgeusia. Imaging studies showed that the region commonly involved was the frontal opercular area corresponding to the taste cortex. CONCLUSION: It is suggested that strokes involving the taste cortex may produce altered food preference associated with decreased taste sensation.

Aged↗
PubMed1983

Zinc metabolism and taste acuity in renal transplant recipients.

To determine the effect of renal transplantation on taste acuity and zinc metabolism, we tested 43 patients with functioning allografts for 2.5 to 96 months. They were tested for taste by the 3-drop stimulus technique. In 30 of them, we determined zinc levels in plasma, hair, and urine. Subnormal plasma and hair zinc, as well as hyperzincuria, was present in all of the 15 patients less than 12 months posttransplant. In contrast, 10 patients who were more than 12 months posttransplant had plasma zinc levels, hair zinc, and urinary zinc excretions in the normal range. Zinc concentrations in plasma and hair of 5 patients who were more than 12 months posttransplant with renal failure, were subnormal and were similar to those in hemodialysis patients. Similarly, taste detection and recognition thresholds for sodium chloride, sucrose, urea, and hydrochloric acid were normal only in patients more than 12 months posttransplant with normal renal function. Plasma zinc, hair zinc, and urinary zinc were not related to prednisone or azathioprine dosage. These results suggest that abnormalities of zinc and taste persist up to 12 months posttransplant and may be related to increased urinary zinc losses.

Adult↗
PubMed1983

[Methodological critical studies of taste using chemical stimuli].

Two methods of the chemical examination of taste were compared in view of its practicability. The "Three-Choice-Technique" is most profitable for the clinical use. It is carried out easily and quickly, and the results permit a sufficient and exact estimation of the taste sensitivity. The "Assorting-Technique" seems to be less useful. It provides lower thresholds, but the expense is higher. The Three-Choice-Technique, the special concentration sequences and the ascertained normal threshold for the four basic taste qualities enable a better registration of taste disturbances, at which side differences are of no consequence.

Adolescent↗
PubMed2005

[Assessment of the correlation between taste and smell functioning].

UNLABELLED: There are few studies examining relationship between taste and smell. However their clinical unity is more often indicated. Smell perception abnormalities cause modification in taste of food intensity, disabling perception of taste as a consequence of taste's sniffing failure. Thus disturbances of these senses, which often commonly coexist could cause great discomfort in patients, however taste sense is estimated as less important comparing to smell sense. The aim of that study was to compare the taste perception in patients with normal smell function and patients with hyposmia and anosmia. There was analyzed correlation between the patients' subjective estimation of smell and taste senses and results of gustometry and olfactometry examinations. MATERIAL AND METHOD: there were indicated three groups of patients based on smell examination with usage of Elsberga--Levy'ego olfactometr in Pruszewicz modification. The first group included patients with normosmia, the second--patients with hyposmia or anosmia related to every smell, the third--patients with hyposmia on few smells and normal smell feeling of others. The Bornstein's method gustometry modified by us was performed for all groups. Moreover patients presented their subjective estimation of smell and taste senses. All results were statistically analyzed, taking into consideration results with alpha < or = 0.05. RESULTS: All (100%) patients with normosmia correctly identified sour, bitter and salty tastes, while only 53% of patients with hyposmia and anosmia got similar results. However 76.5% of patients from the second group subjectively estimated their sense of taste as a normal perception. CONCLUSIONS: Patients with smell disturbances significantly more often have abnormalities in taste perception than patients with normosmia and their subjective estimation of taste and smell senses is much more different than gustometry and olfactometry results.

Adult↗