The goal here is to explore how three stimulus dimensions (thermal, mechanical, and chemical) can operate jointly on each of four different sense modalities to determine perceptual events. These modalities are (1) touch, (2) taste, (3) warmth and cold, and (4) common chemical sense (CSS). The CCS, often slighted by students of the senses, is mediated by receptors in the nose and mouth and plays and double role of (a) protecting against intake of caustics and (b) giving to food and beverages agreeable pungency or """"""""spiciness"""""""" (e.g. peppers, mustards, carbonated and alcoholic beverages). Neuroanatomically these three senses are peripherally distinct, so that """"""""true"""""""" interaction among them supposedly takes place in the CNS. In addition, however, all four receptor types can respond to multimodal stimulation, i.e. to mechanical, thermal, and/or chemical stimulation. For example, our research has revealed that warmth and cold can greatly enhance pressure sensations on the skin, with extensive psychophysical evidence that enhancement takes place through joint thermal and mechanical arousal of touch receptors. This led us to the novel hypothesis that spatial acuity of tough can be sharpened by simultaneous application of thermal and mechanical energy. Pilot work on two-point discrimination favored this hypothesis, and the proposal is to select a battery of tests to assess the role of the thermal component of stimulation in (a) various parts of the body, parametrically, especially glabrous sites, (b) various methods, including the classical two-point discrimination and point localization, but also newer methods, e.g. accuracy of length and area discrimination, and (c) the potential usefulness of thermal stimulation for tactile aids for the deaf and blind. Other previous work showed significant taste-temperature interactions in the mouth. However, there remain potentially important questions about interactions among taste, temperature, and CCS. We will obtain psychophysical scales relating degree of pungency to concentration of two agents: (1) capsaicin (active ingredient in hot red peppers) and (2) ethyl alcohol. We will then seek to quantify what pilot studies here (together with cues from the archival literature) suggest may be important interactions, e.g. possible effects on taste and temperature sensations by CSS and alteration of CSS by thermal input. We will also try to assess long-term exposure to capsaisin by alternation between usage and abstinence.
| Stevens, J C (1990) Perceived roughness as a function of body locus. Percept Psychophys 47:298-304 |
| Stevens, J C (1989) Temperature and the two-point threshold. Somatosens Mot Res 6:275-84 |
