A piece in All Things Considered by Jon Hamilton (NPR or National Public Radio) talks about new research showing that the brain perceives an odor differently if it arrives through the nose (orthonasal) rather than through the mouth (retronasal). The work is described in an article in the journal Neuron where the authors conclude “The main finding of this experiment is that the same odor may produce differential brain responses depending on whether it is sensed orthonasally and experienced as coming from the nose or retronasally and experienced as coming from the back of the mouth.” (Differential Neural Responses Evoked by Orthonasal versus Retronasal Odorant Perception in Humans. Small DM, Gerber JC, Mak YE, Hummel T. Neuron. 2005, 47:593-605.)Short review of the concept.
The most fascinating aspect of the study was that the odor of chocolate showed the greatest effect on route of delivery. This suggests that differences in “response to retronasal versus orthonasal perception is influenced by whether an odor represents a food item”. The interpretation is that sensing of odor orthonasally may help indicate the availability of food while retronasal identification may signify receipt of food. However its early days yet because the study only used one food odor (chocolate) compared to three none food odors (lavender, butanol, farnesol). More food odors need to be studied to see if they give the same result as the chocolate odor.
One interesting point from the NPR audio piece is that if you want to increase your ability to detect non-food odors retronasally then you need to ingest something with that odor. Anyone for a drop of cat pee on their tongue?
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