This proposal is focussed on two long term goals: (1) evaluating the taste worlds of tasters and nontasters of PROP and (2) understanding the ability of the taste system to produce normal real-world experience in the presence of extensive damage to the neural structures subserving taste. Taste thresholds for the bitter substance PROP (6-n-propylthiouracil) show a bimodal distribution leading to the designation 'tasters' for the more sensitive and 'nontasters' for the less sensitive. Family studies suggest that nontasting is a simple Mendelian recessive trait. Thus nontasters are homozygous for the recessive gene while tasters may be either heterozygous or homozygous for the dominant gene. The designation 'nontaster' vs 'taster' suggests that these are the important phenotypes but this may be incorrect. Tasters show considerable variability when they scale PROP. Some find PROP to be much more bitter than others do. One hypothesis to be tested in this project Is that the more appropriate division may be between supertasters (who may be homozygous dominants) and others. This hypothesis will be tested by psychophysical scaling and by a preliminary family study. Individuals with extensive damage to the taste system may have no subjective changes In taste experience. One hypothesis to explain this phenomenon is that there are inhibitory connections in the taste system. Thus if one nerve is damaged, it then fails to send its normal input to the brain but it also fails to send inhibition to other taste nerves. The output of those nerves is thus enhanced.
An aim of this project is to test the release of inhibition hypothesis in two ways. First, anesthesia will be used to block specific loci and observe the effects on taste on other loci. Second, patients will be tested who have taste damage restricted to particular loci to see if they experience enhanced taste on other loci. Finally, particular qualities will be blocked on some loci (by Gymnema sylvestre, an herb that selectively affects sweetness and by adaptation) to test the possibility that the release of inhibition Is quality specific. Another factor in the failure of patients to notice partial taste damage concerns the ability to localize taste. This project will investigate localization illusions that permit taste to appear to come from areas that are known to be devoid of receptors. A new discovery has caused these two lines of research to converge. Nontasters are now thought to have fewer taste buds than tasters. One long-term goal of this research is to determine whether or not nontasters and those who have suffered partial taste losses are at special risk for devastating losses in the future. The capacity of the taste system to cope with damage is remarkable but It is not unlimited. The overall goal of this project is to determine those limits.

Agency
National Institute of Health (NIH)
Institute
National Institute on Deafness and Other Communication Disorders (NIDCD)
Type
Research Project (R01)
Project #
5R01DC000283-10
Application #
2125350
Study Section
Sensory Disorders and Language Study Section (CMS)
Project Start
1989-12-01
Project End
1995-06-30
Budget Start
1994-01-01
Budget End
1995-06-30
Support Year
10
Fiscal Year
1994
Total Cost
Indirect Cost
Name
Yale University
Department
Surgery
Type
Schools of Medicine
DUNS #
082359691
City
New Haven
State
CT
Country
United States
Zip Code
06520
Williams, Johnny A; Bartoshuk, Linda M; Fillingim, Roger B et al. (2016) Exploring Ethnic Differences in Taste Perception. Chem Senses 41:449-56
Snyder, Derek J; Bartoshuk, Linda M (2016) Oral sensory nerve damage: Causes and consequences. Rev Endocr Metab Disord 17:149-58
Coldwell, Susan E; Mennella, Julie A; Duffy, Valerie B et al. (2013) Gustation assessment using the NIH Toolbox. Neurology 80:S20-4
Duffy, Valerie B; Hayes, John E; Davidson, Andrew C et al. (2010) Vegetable Intake in College-Aged Adults Is Explained by Oral Sensory Phenotypes and TAS2R38 Genotype. Chemosens Percept 3:137-148
Hayes, John E; Sullivan, Bridget S; Duffy, Valerie B (2010) Explaining variability in sodium intake through oral sensory phenotype, salt sensation and liking. Physiol Behav 100:369-80
Snyder, Derek J; Bartoshuk, Linda M (2009) Epidemiological studies of taste function: discussion and perspectives. Ann N Y Acad Sci 1170:574-80
Hayes, John E; Duffy, Valerie B (2008) Oral sensory phenotype identifies level of sugar and fat required for maximal liking. Physiol Behav 95:77-87
Bachmanov, Alexander A; Kiefer, Stephen W; Molina, Juan Carlos et al. (2003) Chemosensory factors influencing alcohol perception, preferences, and consumption. Alcohol Clin Exp Res 27:220-31