Quality-specific effects of aging on the human taste system

Abstract

Elderly! persons are known to have elevated taste thresholds, with those for bitter more affected by age, for example, than those for sweet. Do analogous quality-specific effects occur at suprathreshold levels? Young (mean age = 20.3 years, SD = 2.99) and elderly (mean age = 72.5 years, SD = 4.58) subjects made magnitude estimates of sweetness, bitterness, sourness, and saltiness for the unmixed components sucrose, caffeine, citric acid, and NaCI at three concentration levels for each. They also made magnitude estimates of the separate taste qualities in twocomponent mixtures of sucrose with each of the other three qualities, at various levels of the two components in each mixture. Magnitude estimates of taste intensity were interweaved with magnitude estimates of the heaviness of six weights, which subjects were to judge on the same subjective intensity scale: This is the calibration feature of the method of magnitude matching, and permits the comparison of elderly and young subjects on the absolute intensity of tastes.When unmixed components were judged, elderly subjects found the characteristic tastes of caffeine and citric acid less intense than, but those of sucrose and NaCI as intense as, younger subjects did. In judging mixtures, the elderly found bitterness, but not the other three qualities, less intense than did the young subjects.There is evidence that human chemosensitivity lessens with age (for reviews, see Murphy, 1986;Schiffman, 1986). Most psychophysical data on aging of the taste system are from threshold studies, which have demonstrated increased thresholds in the elderly. The effects of aging on taste need not be uniform across taste qualities, since different mechanisms almost certainly subserve the different qualities and more than one mechanism may encode stimuli of the same quality. Murphy (1979) reported quality-specific age effects on taste thresholds. More recent research also shows that there are larger age effects on thresholds for bitter and salty than for sweet and sour stimuli (Weiffenbach, Baum, & Burghauser, 1982).Effects that appear at threshold may disappear at suprathreshold intensities. Is this the case with taste, or are there age-related differences in perceived intensity analogous to the liminal differences? Hyde and Feller (1981) estimated exponents for the four taste qualities, and compared the size of exponents for young and old subjects. The elderly produced smaller exponents than the young did for bitter and sour stimuli (caffeine and citric acid), but not for sweet and salty stimuli(sucrose and NaCI). Cowart (1983) obtained similar results with magnitude estimation, except that she found no age effect on the exponent for citric acid. She also reported impaired ability to dis-

Aging is associated with increased Weber ratios

“…Since human taste papillae can respond to more than one taste quality (Cardello, 1981), a peripheral site for quality-specific age effects would have to be at the level of individual taste buds or cells. The results of the present study further support the idea that in the pursuit of the underlying mechanism for age effects on the human taste system, attention should be given to membrane function and transduction in aging cells (Murphy & Gilmore, 1989). It will be of interest to determine whether age effects are stimulusspecific within the bitter taste quality, since more than one mechanism may encode the bitter taste quality.…”

“…Under these circumstances, magnitude matching will underestimate the effects of age on suprathreshold intensity perception . Similarly, perceptual context probably had some influence on elderly and young persons' judgments of the intensity of bitter and sweet in the magnitude-matching experiment described above (Murphy & Gilmore, 1989). As we noted in our discussion of those results, because the contextual worlds of the elderly and young were probably different, the differences between the two groups may have been even larger than described.…”

“…When we determined psychophysical functions for stimuli representative of the four basic taste qualities in a previous study (Murphy & Gilmore, 1989), the elderly's intensity estimates of bitter were the most depressed relative to young people's estimates, and their intensity estimates of sweet were the least depressed. Therefore, tastants representative of these two taste qualities were examined in the present study, and we hypothesized that larger age differences would be found in the discrimination of bitter, as opposed to sweet, stimuli.…”

“…Rifkin, Marks, & Bars, 1986;Cowart, 1983, in press;Hyde & Feller, 1981;'Murphy & Gilmore, 1989;Spitzer, 1988;Weiffenbach, Baum, & Burghauser, 1982;Weiffenbach, Cowart, & Baum, 1986). When we determined psychophysical functions for stimuli representative of the four basic taste qualities in a previous study (Murphy & Gilmore, 1989), the elderly's intensity estimates of bitter were the most depressed relative to young people's estimates, and their intensity estimates of sweet were the least depressed.…”

Modulation des afférences gustatives linguales par les afférences du nerf alvéolaire inférieure : étude électro-gustomètrique chez l’homme

“…Certaines études avaient pourtant conclu que la sensibilité gustative pourrait diminuer avec le vieillissement. Des études psychophysiques ont signalé une augmentation des seuils de détection [39] ou de la perception [40] avec l'âge, limitée à quelques molécules sapides mais toujours avec de grandes variabilités interindividuelles. Des études électro-gustométriques ont également signalé une augmentation de seuil au-dessus de 60 ans, mais il y avait encore de grandes variations individuelles de sensibilité [41].…”