Investigating Differences in Oral Somatosensation and Viscosity Perception

Open Access
Alcala, Maya Isabella
Area of Honors:
Food Science
Bachelor of Science
Document Type:
Thesis Supervisors:
  • John Hayes, Thesis Supervisor
  • Federico Miguel Harte, Honors Advisor
  • viscosity
  • oral somatosensation
  • point pressure
  • thresholds
  • discrimination
  • detection
  • perception
  • Von Frey Hair
  • Cochet-Bonnet
  • oral touch
  • fluid flow
  • mouth
  • maltodextrin
  • Just Noticeable Difference
  • JND
  • Oral Acuity
Viscosity, the extent to which a fluid resists flow, affects the perception and liking of many foods and beverages. However, the mechanism of human perception of viscosity in the mouth is poorly understood. This study involved measuring oral touch perception and oral viscosity perception to determine if there is any relationship between the two. Detection and discrimination threshold estimates of oral point pressure were measured on the midline superior surface of the tongue just posterior to tongue tip for each participant. Discrimination threshold estimates were determined with commercially available Von Frey Hair monofilaments, while commercially available Cochet-Bonnet Aesthesiometers, which deliver less force, were used to determine detection threshold estimates. Model solutions of maltodextrin were used to assess differences in viscosity perception. Using known Weber fractions, pairs of solutions were formulated, such that viscosity differed by 10% above the Just Noticeable Difference (JND). Participants were presented with the pairs of solutions in a 2-AFC format and asked to identify the thicker of the two solutions. Despite the lower amount of force provided by Cochet-Bonnet Aesthesiometers, I observed a floor effect for detection threshold estimates: there was very little variance in the data as nearly all participants could detect the lowest available test stimuli. Therefore, the discrimination threshold estimates were used for remaining analyses. Point pressure discrimination threshold estimates showed sufficient variance to allow separation of participants into high and low discrimination groups, similar to prior work. However, when the viscosity discrimination results of these two groups were analyzed with Fisher’s exact tests, there was no evidence to suggest that oral point pressure discrimination ability was associated with viscosity perception. For the low series viscosity samples, of the group with better oral acuity, 16 of 26 (61.5%) correctly identified the more viscous sample, while the group with less oral acuity had 24 of 34 (70.5%) correct identifications. This difference was not significant at a p-value of 0.05. Similar results were observed for the high series viscosity samples, with 14 of 26 (53.9%) correct identifications by those with better oral acuity and 17 of 34 (50.0%) correct identifications by the less acute individuals. These data suggest mechanisms of viscosity perception are not related to phenotypic differences in oral somatosensation when using point-pressure assessments. Future work is needed to develop a more sensitive and verified instrument that may yield more conclusive results in regard to detection thresholds. Also, it may be beneficial to explore roughness discrimination, as it may provide a better indication of an individual’s ability to distinguish viscosity.