Taste perception with age

Keywords: age, thresholds, supra-threshold intensities, pleasantness, optimally preferred concentration, olfactory deprivation,signal-to-noise ratio

This thesis describes experiments studying age-related diferences in taste perception. Thresholds, supra-threshold intensities and pleasantness for ten different tastants, representing the five taste qualities sweet, sour, salty, bitter and umami were measured in the same group of elderly and young subjects. The tastants were dissolved in water and in product. Age has a deteriorating effect on taste sensitivity, which is already noticeable in the young-old group of elderly. First, this effect is generic in nature, i.e. more than 90% of the total variance attributable to age is due to age alone and less than 6% to age-related differences in the perception of the different taste qualities. Secondly, the differentiation between the different taste qualities is less distinct for elderly than for young people. A change in the signal-to-noise ratio at neural or perceptual level might be put forward to explain these phenomena. The outcome might support the hypothesis that the primary taste cortex is the locus of most accurate coding. Neither thresholds nor supra-threshold sensitivity were good predictors of the most preferred concentration of the tastants in product. Although the perceived intensities were lower for the elderly than for the young, the most preferred concentration of the tastants in product were similar for both age groups. It is suggested that the information about perception and affection might be processed in different regions of the brain. The most intriguing finding in this thesis is that smell seems to play a crucial role in taste perception. When the olfactory input is blocked, about 70% of the age differences in taste perception disappeared. Since taste and smell are so intimately related and accompanied by other sensations, such as mouthfeel, temperature and spiciness, it might not be a bad idea to investigate taste perception with a multimodal/multimethod approach, including all oral sensations in the investigation.