It has become abundantly clear that aging takes a toll on all three chemical senses: taste, smell, and common chemical sense (CCS). Of these, taste seems the most resilient; although old people, on the average, lose the ability to detect faint levels of tastes, the perception of supra-threshold taste magnitudes remains relatively intact. In contrast, losses of smell and CCS frequently pervade the entire sensory continua from low to high stimulus levels. These are accompanied by loss of ability to identify and discriminate odors. The present proposal concerns the relation of olfactory and CCS losses to other aspects of chemosensory function about which much is known from youthful persons, and concerning which there is reason to hypothesize that aging might matter. These include (a) Olfactory affect, or the perception of the pleasant-unpleasant dimension of odors, the main question being to what extent affective narrowing takes place in old age and to what extent it pertains to the loss of suprathreshold magnitude; (b) Olfactory memory, or the ability to recognize odors shortly after inspection and then at intervals of a day and a week. Questions of interest include: the relation of odor recognition to olfactory identification and discrimination, to visual recognition, and to gender. (c) Adaptation, or loss of sensitivity over time with ongoing stimulation, especially as regards its role in the detection of a gas warning agent, ethyl mercaptan; (d) Olfactory--CCS mutual inhibition, or the power of nasal irritants to mute smells, and vice versa; (e) Detection of danger-related substances, in the present study the ability to detect smoke and ethyl mercaptan; and (f) Age-related dementia (especially Alzheimer's disease) as it affects three basic functions of olfaction: detection, odor identification, and perception of the affective dimension, i.e., the capacity to discriminate between good and bad odors and tastes.
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