Retronasal odor representations in the dorsal olfactory bulb of rats

Animals perceive their olfactory environment not only from odors originating in the external world (orthonasal route) but also from odors released in the oral cavity while eating food (retronasal route). Retronasal olfaction is crucial for the perception of food flavor in humans. However, little is...

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Bibliographic Details
Published in:The Journal of neuroscience 2012-06, Vol.32 (23), p.7949-7959
Main Authors: Gautam, Shree Hari, Verhagen, Justus V
Format: Article
Language:English
Subjects:
Analysis of Variance
Animals
Data Interpretation, Statistical
Electrophysiological Phenomena
Female
Mouth - innervation
Mouth - physiology
Nasal Cavity - innervation
Nasal Cavity - physiology
Neuroimaging
Odorants
Olfactory Bulb - physiology
Olfactory Pathways - physiology
Olfactory Receptor Neurons - physiology
Rats
Rats, Long-Evans
Respiration
Smell - physiology
Taste - physiology
Volatilization
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Summary:Animals perceive their olfactory environment not only from odors originating in the external world (orthonasal route) but also from odors released in the oral cavity while eating food (retronasal route). Retronasal olfaction is crucial for the perception of food flavor in humans. However, little is known about the retronasal stimulus coding in the brain. The most basic questions are if and how route affects the odor representations at the level of the olfactory bulb (OB), where odor quality codes originate. We used optical calcium imaging of presynaptic dorsal OB responses to odorants in anesthetized rats to ask whether the rat OB could be activated retronasally, and how these responses compare to orthonasal responses under similar conditions. We further investigated the effects of specific odorant properties on orthonasal versus retronasal response patterns. We found that at a physiologically relevant flow rate, retronasal odorants can effectively reach the olfactory receptor neurons, eliciting glomerular response patterns that grossly overlap with those of orthonasal responses, but differ from the orthonasal patterns in the response amplitude and temporal dynamics. Interestingly, such differences correlated well with specific odorant properties. Less volatile odorants yielded relatively smaller responses retronasally, but volatility did not affect relative temporal profiles. More polar odorants responded with relatively longer onset latency and time to peak retronasally, but polarity did not affect relative response magnitudes. These data provide insight into the early stages of retronasal stimulus coding and establish relationships between orthonasal and retronasal odor representations in the rat OB.
ISSN:1529-2401
0270-6474
1529-2401
DOI:10.1523/JNEUROSCI.1413-12.2012