Regional Taste Sensitivity to NaCl: Relationship to Subject Age, Tongue Locus and Area of Stimulation

Abstract

Using a signal detection procedure and a microprocessor-controlled gustometer, sensitivity to three concentrations of NaCl (0.01, 0.1 and 1.0 M) was measured on the tongue tip, and on a region 3.0 cm posterior to the tongue tip in 12 young (20-29 years of age) and 12 elderly (70-79 years of age) subjects. Stimulus duration was 2 s; the sizes of the tongue areas stimulated were 12.5, 25 and 50 mm2. On average, the young subjects were more sensitive to NaCl on the tongue tip than on the more posterior stimulation site and exhibited, at both tongue loci, an increase in detection performance as stimulus concentration increased. The elderly subjects, on the other hand, performed at chance level at both tongue loci for all three stimulus sizes and concentrations tested. No sex differences were observed. In the young subjects, the mean R-index increased monotonically as a function of stimulus size for the two highest NaCl concentrations at both tongue loci. A hyperbolic function provided the best fit to these data at the tongue tip, and an exponential function at the more posterior tongue region, implying a different pattern of spatial summation at these two sites. Overall, this study demonstrates that marked age-related changes in regional taste sensitivity to NaCl are present in elderly persons.

Anorexia, undernutrition, weight loss, sarcopenia, and cachexia of aging

“…The four primary tastes (salt, bitter, sweet, and sour) will decrease with aging [88]. Also, older persons lose the increased sensitivity of the tongue tip that is seen in younger persons [39]. Other factors, such as smoking, medications, xerostomia, and local inflammatory conditions can interfere with taste acuity.…”

Regional Differences in Suprathreshold Intensity for Bitter and Umami Stimuli

“…Indeed, taste thresholds may vary across the tongue (Collings 1974). Some work suggests that recognition for salt declines with age, and that in younger people, sensitivity to salt is greater on the tongue tip than the posterior region (Matsuda and Doty 1995). Whether this also applies to suprathreshold intensity is unclear.…”

The Temporal Automated System for Taste Experiments (TASTE)

“…A higher threshold for the flow procedure in comparison with the sip-and-spit procedure is not surprising, given that the TASTE system stimulates a smaller portion of the tongue, over what is undoubtedly a shorter stimulus duration. There is considerable evidence of both spatial summation and temporal summation in taste perception (see, e.g., Linschoten & Kroeze, 1991, 1992Matsuda & Doty, 1995). Given these considerations, the present data indicate that the TASTE system can be effective and useful in the study of gustatory perception.…”