RETRONASAL OLFACTION IN AGING--CONTRIBUTIONS OF TASTE

University Of Connecticut Storrs, Storrs-Mansfield CT

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Abstract

The long-term goal of this research is to understand how variation in oral sensation influences the ability of older adults to manage disease risk through food intake. One source of variation is age-associated declines in olfaction. Olfaction serves a dual role in perceiving the food world: food aromas are both drawn from the environment through the nares (orthonasal olfaction) and pumped into the nasal cavity from the mouth during chewing and swallowing (retronasal olfaction). Although each path delivers odorants to the same olfactory receptors, retronasal olfaction is perceptually localized to the mouth ("flavor"). Older adults with poorer retronasal olfaction can show dietary behaviors that increase the risk of chronic diseases. In addition to factors that damage the olfactory system, impaired retronasal olfaction can result from factors that interfere with olfactory processing in the mouth. The hypothesis under evaluation is that taste helps localize retronasal olfaction perceptually to the mouth; a loss of taste disturbs that localization leading to reduced retronasal olfaction ("flavor"). Preliminary data show that unilateral anesthesia of the chorda tympani nerve (taste, anterior tongue) reduces flavor where taste is absent (anterior side of anesthesia) and localizes flavor to the area that taste is still present or even enhanced (posterior side, contralateral to anesthesia). This project will examine loss of chorda tympani nerve taste on retronasal olfaction in two concurrent experiments. One experiment will determine whether or not elderly women with chorda tympani taste loss experience reduced retronasal olfaction. Chorda tympani taste is vulnerable to damage as we age (eg, exposure to viruses, head trauma). The second experiment examines a potential model for taste and retronasal interactions in aging. Young, healthy women and men will undergo temporary unilateral and bilateral anesthesia of the chorda tympani nerve (conducted by an otolaryngologist) to determine whether or not retronasal olfaction is reduced. Both experiments will use new psychophysical methodologies to quantify oral sensation. Genetic variation in taste and oral somatosensation will be characterized on all subjects using psychophysical measures as well as counts of fungiform papillae (the structures on the anterior tongue that hold taste buds). This will allow us to evaluate multiple sensory systems that form oral sensation.