Abstract
Links between some psychological disorders and olfactory deficits are well documented, and screening tests have been developed to exploit these associations. Odors can take one of two routes to the olfactory receptors in the nasal epithelium, the orthonasal or retronasal route. This article discusses the potential use of the retronasal route to assess olfaction using gelatin-based stimuli delivered orally. Using a relatively new psychophysical method, the Single-Interval Adjustment Matrix task, we estimated vanillin thresholds for five healthy participants sampling small vanillin flavored gels. Our data demonstrate the feasibility of using solid-state gustatory stimuli to assess retronasal perception.
Highlights
Impairment of olfactory function, including odor identification, is implicated in numerous psychopathologies (Killgore, Killgore, Mcbride, Kamimori, & Balkin, 2008; Martzke, Kopala, & Good, 1997)
Whereas orthonasal olfaction occurs through the inspiration of odorants through the external nares of the nose, retronasal olfaction is dependent upon exhalation or swallowing, which coincides with the migration of odorants through the posterior nares of the nasopharynx (Diaz, 2004; Masaoka, Satoh, Akai, & Homma, 2010)
The rate of descent of the function clearly demonstrates the efficiency of the Single-Interval Adjustment Matrix (SIAM) procedure to rapidly converge on the vanillin threshold, echoing previous research undertaken in the gustatory modality using this technique (Hautus et al, 2010)
Summary
Impairment of olfactory function, including odor identification, is implicated in numerous psychopathologies (Killgore, Killgore, Mcbride, Kamimori, & Balkin, 2008; Martzke, Kopala, & Good, 1997). The perception of odorants is mediated by two independent sensory pathways (Heilmann & Hummel, 2004): the nasal route (i.e., orthonasal olfaction) and the oral/nasopharynx route (i.e., retronasal olfaction). The orthonasal route involves airborne aromatics being drawn through the nostrils upon inhalation, this being what we normally associate with nasal breathing. The retronasal route involves the migration of volatile chemicals to the olfactory receptors embedded in the olfactory mucosa by way of the nasopharynx cavity. Whereas orthonasal olfaction occurs through the inspiration of odorants through the external nares of the nose, retronasal olfaction is dependent upon exhalation or swallowing, which coincides with the migration of odorants through the posterior nares of the nasopharynx (Diaz, 2004; Masaoka, Satoh, Akai, & Homma, 2010)
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