Taste and smell perception in aging.
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Adult↗
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Taste of glutamate salts in young and elderly subjects: role of inosine 5'-monophosphate and ions.
Taste sensitivity to five glutamate salts (sodium glutamate, potassium glutamate, ammonium glutamate, calcium diglutamate, and magnesium diglutamate) were determined in sixteen young (mean age 25.58 years) and eighteen elderly (mean age 86.89 years) subjects. The effect of inosine 5'-monophosphate (IMP) and ions on taste perception of glutamate compounds was also investigated. The detection thresholds for glutamate salts were 5.04 times higher in elderly subjects than in young subjects; the recognition thresholds were 3.84 times higher. For young subjects, 0.1 mM IMP lowered detection and recognition thresholds for all 5 salts. A stronger concentration of IMP (1 mM) had this effect in both young and elderly groups. Elderly subjects perceived suprathreshold concentrations as less intense than young subjects. Chloride and acetate salts of sodium, potassium, and calcium reduced the detection and recognition thresholds of L-glutamic acid but had no effect sodium glutamate thresholds.
Adult↗
On-line psychophysical data acquisition and event-related fMRI protocol optimized for the investigation of brain activation in response to gustatory stimuli.
An experimental method for event-related functional magnetic resonance imaging that allows for the presentation of several chemosensory stimuli in the oral cavity during the same run, the collection of psychophysical measures (intensity or pleasantness) during the presentation of the stimuli, and the analysis of the data in an event-related fashion are described. The automatic pumps used to present taste stimuli allowed for multiple tastes to be delivered in small amounts under computer control. Psychophysical ratings of pleasantness or intensity were collected after each presentation of a taste stimulus and water, with the general labeled magnitude scale, using a joystick that controlled the movement of an arrow on the visual display. Performing these cognitive tasks required that the participant remained focused, and aided in the interpretation of the data collected. The perceived pleasantness differed across stimuli for all conditions; however, pleasantness ratings for the same stimulus displayed consistency, over the duration of the run and before each scan on separate days. Activation in response to sucrose and caffeine while the participant rated pleasantness was found in the insula, frontal operculum, rolandic operculum and orbitofrontal cortex which is consistent with previous taste fMRI studies.
Adult↗
Assessment of patients with taste and smell disorders.
The evaluation of patients with taste and smell complaints is difficult without standardized quantitative methods of assessment. This paper summarizes recent developments in the evaluation of chemosensory patients. Evaluation must begin with a careful medical history, since certain questions can help in establishing an etiology. Several recent advances have been made in the development of standardized tests for the assessment of taste and olfactory function. Smell can be evaluated with a combination of butanol threshold and odor identification (University of Connecticut test battery) and with the University of Pennsylvania Smell Identification Test (UPSIT). Scores obtained from 91 patients show good correlation between these two testing procedures. Both tests provide normative data for comparison, with the UPSIT including both age- and sex-related norms. Traditional evaluation of taste deficits with threshold procedures has been questioned. Measures of suprathreshold taste intensity require the anchoring of taste judgements to another, presumably normal, modality. This has been approached using magnitude matching, in which taste and auditory loudness are judged on the same scale. Spatial testing of the tongue and soft palate can reveal pathology of the gustatory nerves or their central connections. Further understanding of taste and olfactory dysfunction will be facilitated by the development of standardized methods of evaluation.
Humans↗
A role for the right anterior temporal lobe in taste quality recognition.
We conducted two experiments to examine central processing of the taste of citric acid. In the first experiment, elevated citric acid recognition thresholds, but normal detection thresholds, were observed in a group of patients who had undergone a right anterior temporal lobectomy for the treatment of epilepsy, compared with a control group and a group of patients who had undergone the same operation in the left hemisphere. In the second study, using positron emission tomography, we compared regional cerebral blood flow (rCBF) in a condition in which citric acid was presented with one in which water was presented (with similar somatosensory stimulation across both conditions). We observed increased rCBF bilaterally in the caudolateral orbitofrontal cortex, in the right anteromedial temporal lobe, and in the right caudomedial orbitofrontal cortex. The elevated recognition thresholds exhibited in patients with resection of the right anteromedial temporal lobe may be accounted for by damage in an area corresponding to that of the rCBF increase. These results suggest that although taste sensation may be computed in the primary taste cortex, recognition requires further processing by structures located in the anteromedial temporal lobe. Furthermore, they point to preferential processing of this higher-order gustatory function by the right cerebral hemisphere.
Adolescent↗
Taste sensitivity to 6-n-propylthiouracil predicts acceptance of bitter-tasting spinach in 3-6-y-old children.
BACKGROUND: Understanding what motivates the preference for and selection of foods has important health implications. Research suggests that the phytochemicals present in green leafy vegetables contain anticarcinogenic properties. As a result of the bitter taste of phytochemical compounds, however, foods containing these are often not well accepted, particularly by children. OBJECTIVE: We aimed to study the relation between sensitivity to the bitter taste of 6-n-propylthiocuracil (PROP) and acceptance of bitter- and strong-tasting foods in 3-6-y-old children. DESIGN: Two independent procedures, a threshold detection and a suprathreshold intensity task, were used to measure individual sensitivity to PROP, and 3 independent tasks were used to assess food acceptance. RESULTS: Sensitivity to the bitter taste of PROP was positively correlated with dislike of the taste of raw spinach (P < 0.05). CONCLUSIONS: The acceptance of spinach may to some extent be mediated by individual taste perception and be predictable via both threshold and suprathreshold measures of PROP taste sensitivity. Furthermore, children as young as 3 y of age can partake in direct investigations of taste, reliably comply with test procedures, and accurately communicate taste perceptions and preferences under study conditions.
Child, Preschool↗
Hypogeusia, dysgeusia, hyposmia, and dysosmia following influenza-like infection.
Hypogeusia, with or without dysgenusia, and hyposmia, with or without dysosmia, followed an influenzal-like infection in 87 of 143 consecutive patients who presented at the Taste and Smell Clinic at the NIH with taste and smell abnormalities. Findings in this disease included pale nasal mucous membranes with marked patency of the nasal airway, a postive Rudolph sign, elevated detection and recognition thresholds for several tastants and odorants, disruption of the pore region of the tast dub observed on electron microscopy and infiltration of the upper lamina propria of the nasal mucous membrane wih chronic inflammatory cells observed on light microscopy. These findings, taken together, are relatively specific for the diagnosis of this surprisingly common disorder.
Adult↗
Determination of the odor threshold concentrations of chlorobrominated anisoles in water.
Trihalophenols, which are drinking water disinfection byproducts (DBPs) formed by chlorination or chloramination practices, can be biomethylated into trihalogenated anisoles. These latter compounds have traditionally been suspected of causing odor episodes in drinking water around the world. The odor threshold concentration (OTC) of mixed chlorobrominated anisoles, which were previously synthesized, was determined by flavor profile analysis (FPA) performed by an experienced panel trained to identify odors and tastes in water. The odor threshold amount (OTA) was evaluated by using a gas chromatograph equipped with olfactometry (GC-O) and electron capture detectors (ECD). FPA results for mixed chlorobromoanisoles gave a theoretical OTCs range from 2 to 30 ng/L, the 2,6-diBr-3Cl-anisole being the most odorous compound. Rubber is the general descriptor described by panelists for these compounds, although earthy and musty are the following most cited descriptors.
Anisoles↗
Simulated microgravity [bed rest] has little influence on taste, odor or trigeminal sensitivity.
Anecdotal evidence suggests that astronauts' perceptions of foods in space flight may differ from their perceptions of the same foods on Earth. Fluid shifts toward the head experienced in space may alter the astronauts' sensitivity to odors and tastes, producing altered perceptions. Our objective was to determine whether head-down bed rest, which produces similar fluid shifts, would produce changes in sensitivity to taste, odor or trigeminal sensations. Six subjects were rested three times prior to bed rest, three times during bed rest and two times after bed rest to determine their threshold sensitivity to the odors isoamylbutyrate and menthone, the tastants sucrose, sodium chloride, citric acid, quinine and monosodium glutamate, and to capsaicin. Thresholds were measured using a modified staircase procedure. Self-reported congestion was also recorded at each test time. Thresholds for monosodium glutamate where slightly higher during bed rest. None of the other thresholds were altered by bed rest.
Adult↗
Neuroblastoma cell as a model for a taste cell: mechanism of depolarization in response to various bitter substances.
The mouse neuroblastoma cell (N-18 clone) was used as a model for a taste cell. The N-18 cell was found to be reversibly depolarized by various bitter substances. The minimum concentrations of bitter substances which induced depolarization (threshold concentration) varied greatly with the type of the substance. There was a good correlation between the threshold concentrations for various bitter substances in the N-18 cell and those in the human taste responses. The input membrane resistance was little changed during the depolarization induced by the bitter substances. Replacement of Na+ and Cl- with impermeable ions had practically no effect on the depolarization response to the bitter substances and reduction of calcium concentration from 1.8 to 0.2 mM led to a slight increase in the responses. It was suggested that the depolarization of the N-18 cell by bitter substances mainly stems from changes in the phase-boundary potential at the outer surface of the cell.
Animals↗
The merging of the senses: integration of subthreshold taste and smell.
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Adult↗
[Pathophysiologic role of the level of taste sensitivity to table salt and its determination during treatment of hypertension with diuretics].
Sixty hypertensive patients (stage IIB, no complications) were studied. Gustatory sensitivity threshold to salt was determined and body fluid volume, extracellular fluid volume, intracellular fluid volume, circulating plasma volume and interstitial fluid volume were measured in the control period and 2-3 weeks after treatment with diuretics. 27, 63 and 10% of patients had low, moderate and high gustatory sensitivity threshold, respectively. Patients with different gustatory sensitivity threshold to salt were identical in body fluid volume with peculiar extracellular fluid distribution between intravascular and interstitial spaces. In patients (72%) with a favourable hypotensive effect of diuretic therapy the reduction in gustatory threshold to salt was significant.
Adult↗
Taste in the monkey cortex.
The sense of taste in humans differs substantially from that of rodents, from which a preponderance of gustatory electrophysiology derives. To establish a more appropriate neural model for human gustation, we recorded the activity of single neurons in the primary taste cortex in 11 alert cynomolgus macaques. Taste cells composed 6% of all neurons encountered. Another 24% responded during mouth and jaw movements, and 4% were sensitive to tactile stimulation of the mouth. Smaller numbers responded during olfactory or visual stimulation, or when the monkey extended his tongue. Taste cells could be divided into four statistically independent groups, corresponding to those most responsive to glucose (38%), NaCl (34%), quinine (22%), or HCI (5%). The location of a taste cell did not predict its response profile, i.e., there was no clear topographic organization of taste sensitivity. We established neural thresholds and intensity-response functions to the basic stimuli and determined that-with the exception of HCl, to which the macaque is relatively insensitive-they were similar to those reported by human subjects. We then turned to the coding of taste quality, as inferred in macaques from the patterns of neural activity elicited by each of greater than 100 stimuli. The results proved generally faithful to human reports of the perceived qualities of these same tastants. Finally, an investigation of taste mixtures revealed a degree of mixture suppression and interaction among basic qualities similar to those reported by humans. We conclude that the alert macaque offers a reliable neural model for human gustation.
Animals↗
Quantitative studies, taste reconstitution, and omission experiments on the key taste compounds in morel mushrooms (Morchella deliciosa Fr.).
Sensory-directed fractionation of an aqueous extract prepared from morel mushrooms led to the identification of gamma-aminobutyric acid as the chemical inducer of the mouth-drying and mouth-coating oral sensation imparted by morels. Additionally, L-glutamic acid, L-aspartic acid, succinic acid, and the previously unknown (S)-malic acid 1-O-beta-D-glucopyranoside, coined (S)-morelid, were detected as additional important umami-like taste compounds. To further bridge the gap between pure structural chemistry and human taste perception, 33 putative taste compounds were quantified in an aqueous morel extract and then rated for their taste contribution on the basis of dose-over-threshold factors. To confirm these quantitative results, an aqueous taste reconstitute was prepared by blending aqueous solutions of 16 amino acids, 6 organic acids, 3 purines, 4 carbohydrates, 3 minerals, and (S)-morelid in their "natural" concentrations. Triangle tests revealed that the taste profile of this biomimetic organoleptic cocktail did not differ significantly from the taste profile of authentic morel extract. To finally narrow down the number of key taste compounds, taste omission experiments were performed demonstrating that (S)-morelid together with L-glutamic acid, L-aspartic acid, malic acid, citric acid, acetic acid, and gamma-aminobutyric acid are the key organoleptics of morel extract. Moreover, sensory experiments with model solutions showed that (S)-morelid not only imparts a sour and umami-like taste but is able to amplify the taste activity of monosodium glutamate, as well as sodium chloride, solutions.
Adult↗
Sodium taste detectability in rats is independent of anion size: the psychophysical characteristics of the transcellular sodium taste transduction pathway.
There are two known sodium transduction pathways in the rat gustatory system. The transcellular pathway is blocked by amiloride, and the paracellular pathway is limited by the anion gluconate. The contribution of each pathway to sodium detection was assessed. Sodium gluconate (NaGlu) and NaCl thresholds did not differ, implying that the paracellular pathway is not necessary for normal sodium detection. Adding 100 microM amiloride raised both NaCl and NaGlu thresholds but did not abolish all performance to NaGlu, indicating that some chemical cue was present at high concentrations. Rats were also exposed to one of three NaCl diets (0.12%, 1.0%, or 6.0% NaCl) through maternal and ad lib intake from Embryonic Day 1 through testing in adulthood. No differences across dietary groups were found for NaCl or NaGlu threshold with or without amiloride. Thus, this developmental dietary treatment does not appear to affect taste sensitivity to sodium subserved through either transduction pathway. Collectively, these data suggest that the transcellular transduction pathway is both necessary and sufficient for normal sodium detection.
Animals↗
[Smell and taste abilities in workers in the chemical and metalworking industries. (Olfactometric and elgustometric threshold studies)].
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Adolescent↗
Aspects of ingestive behavior in cattle.
Ingestive behavior in cattle differs from other species because of physiological mechanisms developed pari passu with fermentative digestion. The secondary refection of rumination allows remastication and reinsalivation of the large bulk of vegetable food ingested. The need to buffer acid products of cellulose digestion demands continuous high secretion of alkaline saliva. Nervous and hormonal stimuli emanating from the gastrointestinal tract evoke centrally controlled behavior of hunger and satiety. The four primary taste receptors occur in cattle but thresholds are low. Because of the low Na level in plants, cattle have developed the behavior of seeking salt by taste and smell. During Na deficiency it can be shown that cattle readily learn and develop memory, providing a powerful behavioral dimension in the search for food.
Animals↗
Sensory acceptance of Japanese green tea and soy products is linked to genetic sensitivity to 6-n-propylthiouracil.
Genetic sensitivity to 6-n-propylthiouracil (PROP), a heritable trait, has been linked to increased sensitivity to and increased dislike of other bitter compounds. Many phytochemicals with reputed chemopreventive activity have a bitter taste. This study tested the hypothesis that PROP-sensitive women would be more likely to reject Japanese green tea and selected soy products. Both foods contain bitter flavonoids that are thought to be useful in cancer prevention and control. Study subjects, 53 normal-weight, healthy young women, were divided into PROP nontasters (n = 14), regular tasters (n = 28), and supertasters (n = 11) on the basis of their PROP detection thresholds and mean response ratios to PROP compared with NaCl solutions. The subjects tasted a range of soy products, including tofu, miso, plain soymilk, vanilla-flavored soymilk, and five different concentrations of Japanese green tea. Taste intensity and hedonic preference ratings were measured using nine-point category scales. PROP sensitivity was linked to greater perceived bitterness and increased dislike of Japanese green tea. PROP tasters and supertasters preferred vanilla-flavored soymilk over other soy products. Genetic taste markers may alter dietary exposure to substances thought to affect cancer risk.
Adult↗