Anatomical Contributions to Odorant Sampling and Representation in Rodents: Zoning in on Sniffing Behavior

• Published in: Chemical senses 2006-02, Vol.31 (2), p.131-144
• Main Authors: Schoenfeld, Thomas A., Cleland, Thomas A.
• Format: Article
• Language: English
• Subjects: Animals; Behavior, Animal - physiology; Odorants; odotopic; olfactory airspace; olfactory bulb; Olfactory Bulb - anatomy & histology; Olfactory Bulb - physiology; olfactory coding space; Olfactory Receptor Neurons - anatomy & histology; Olfactory Receptor Neurons - physiology; rhinotopic; Rodentia - anatomy & histology; Rodentia - physiology; Smell - physiology; zonation hypothesis
• ISSN: 0379-864X; 1464-3553
• DOI: 10.1093/chemse/bjj015

Odorant sampling behaviors such as sniffing bring odorant molecules into contact with olfactory receptor neurons (ORNs) to initiate the sensory mechanisms of olfaction. In rodents, inspiratory airflow through the nose is structured and laminar; consequently, the spatial distribution of adsorbed odorant molecules during inspiration is predictable. Physicochemical properties such as water solubility and volatility, collectively called sorptiveness, interact with behaviorally regulable variables such as inspiratory flow rate to determine the pattern of odorant deposition along the inspiratory path. Populations of ORNs expressing the same odorant receptor are distributed in strictly delimited regions along this inspiratory path, enabling different deposition patterns of the same odorant to evoke different patterns of neuronal activation across the olfactory epithelium and in the olfactory bulb. We propose that both odorant sorptive properties and the regulation of sniffing behavior may contribute to rodents' olfactory capacities by this mechanism. In particular, we suggest that the motor regulation of sniffing behavior is substantially utilized for purposes of “zonation” or the direction of odorant molecules to defined intranasal regions and hence toward distinct populations of receptor neurons, pursuant to animals' sensory goals.