When foods and beverages are placed in the mouth, taste sensations occur via chemical excitation of specialized receptors on the tongue, palate, and throat. At the same time, odor molecules rising up the back of the throat excite olfactory receptors, a process known as retronasal olfaction (RO). While taste and RO cues contribute distinct information to the composite experience of flavor, mounting evidence suggests that RO perception requires oral input. Objective: To explore interactions between oral sensation and RO, subjects sampled food items before and after topical anesthesia of the mouth (which suppresses taste and oral tactile sensation). We predicted that retronasal olfaction would decrease after oral anesthesia, and that this effect would be most pronounced in supertasters of 6-n-propylthiouracil (PROP). Methods: Using the General Labeled Magnitude Scale (gLMS), subjects (n = 32) were trained to rate the intensity of various sensory stimuli, including a filter paper impregnated with PROP. Subjects then sampled several food items (strawberry yogurt, strawberry fruit roll-up, milk chocolate, ketchup) before and after rinsing the mouth with 0.5% dyclone. Subjects placed each sample in the mouth with the nose plugged, rated taste intensity, and then unplugged the nose while swallowing the sample to rate RO. Results: RO intensity (averaged across all foods) declined significantly following oral anesthesia (p < 0.001); rising PROP intensity was associated with greater RO deficits (p < 0.03). Conclusion: Retronasal olfaction decreases when oral sensory input is blocked, presumably via central neural circuits linking food-related cues. (Supported by a UFCD Student Summer Research Fellowship and NIH DC 00283.)

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