Mechanisms of Taste- & Taste-Olfaction Mixture Detection

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DESCRIPTION (provided by applicant): Most foods and beverages have 'tastes' (or, more appropriately, 'flavors'), and these result from the integration of neural inputs deriving from several sense modalities: gustation, or taste proper; olfaction; and even somatosensation (touch, temperature, sometimes pungency or irritation). Further, most stimuli that produce perceptions of taste and flavor consist of mixtures of large numbers of individual chemical constituents, and the perception of mixtures depends ultimately on central neural mechanisms that integrate signals arising within and among modalities. The present research focuses on mechanisms underlying the detection, by humans, of taste mixtures (mixtures of gustatory stimuli) and taste-olfactory mixtures (mixtures of gustatory and olfactory stimuli) when stimuli are flowed over the tongue or taken into the mouth. It is likely that at least four neural channels can operate independently in the threshold-level detection of gustatory and olfactory taste/flavor stimuli. Given this, and given that detection reflects discrimination of signal from noise (signal detection theory), a series of experiments will test the predictions of a quantitative model of central integration of statistically independent channels. This model, the integration model, predicts partial summation of signals arising from stimuli that activate independent channels. Tested also are two alternative quantitative models. One of these, a model of complete independence, predicts probability summation, which implies less summation than that predicted by the integration model; the other alternative, stimulus summation, is a model that assumes that stimuli have additive effects within a single channel, and this model typically predicts greater summation than does the integration model. The first set of experiments measures sensitivity to mixtures of gustatory and olfactory stimuli taken in the mouth. The second set of experiments measures sensitivity to mixtures of gustatory stimuli. The third set of experiments asks whether subjects are able to use probability summation to improve the detection of taste-olfaction mixtures. And the fourth set of experiments tests the hypothesis that channel-independence will fail in a paradigm of cross-channel cross modal, gustatory-olfactory) masking, when background maskers are well above threshold.