Ortho- and Retronasal Presentation of Olfactory Stimuli Modulates Odor Percepts

Abstract

Retronasal olfaction gives us information important not only for the well-being by detecting dangerous substances but also provides a basis for the pleasures of eating and drinking. However, odors presented via the retronasal route appear to evoke different sensations compared to orthonasal presentation. In this study, we differentially stimulated anterior and posterior parts of the subjects' nasal cavity with odors. Subjects were able to tell retronasal and orthonasal smelling apart; the ability of doing so seemed to be linked to but could not completely be explained by the degree to which the odorant stimulated the trigeminal nerve. Furthermore, we examined whether food and nonfood odors were perceived as differently pleasant, depending on the presentation site. In fact, some but not all nonfood odors were described as less pleasant when they were delivered retronasally. In conclusion, the present results clearly suggest that there are differences between sensations produced by presenting odors through the retronasal or the orthonasal route, which bears significance for both basic and applied research.

Reversible obstruction of the olfactory cleft: impact on olfactory perception and nasal patency

“…Orthonasal and retronasal odor pairs were rated comparably in regard to pleasantness. Previous authors found a similar relation for food odors in contrast to nonfood odors 26 . Hedonic ratings did not change as pronouncedly as intensity ratings following foam application, supporting the discussed associations.…”

The role of trigeminal function in the sensation of nasal obstruction in chronic rhinosinusitis

“…Such manipulation was not performed in the group analyses ( t test) in an effort to avoid introducing a bias in group means. Finally, individual performance on the trigeminal lateralization task was analyzed as a categorical variable (pass/fail), in which scores above 25 (out of 40) were regarded as significantly above chance level (i.e., pass) according to binomial distribution ( P < .05) . χ 2 analysis was then performed to compare pass rates between the study groups.…”

Perception of specific trigeminal chemosensory agonists

“…After each trial, subjects made a two-alternative (left/right), forced-choice judgement on the position of the stimulus by raising the corresponding hand. Task performance was assessed by counting the number of correct lateralizations (von Skramlik, 1924, von Békésy, 1964, Kobal et al, 1989, Hummel et al, 2003, Wysocki et al, 2003, Frasnelli et al, 2008) resulting in a score for each stimulus. Tests of different stimuli were separated by a 10-minute break.…”

“…An interesting feature in humans that sets the trigeminal system apart from its olfactory counterpart is its ability to physically identify the site of stimulation (von Skramlik, 1924, Frasnelli et al, 2008). When an odorous stimulus is presented to one nostril only (monorhinal stimulation) we can only identify the stimulated nostril, if the odor also activates the trigeminal system (Kobal et al, 1989, Hummel et al, 2003, Frasnelli et al, 2009, Kleemann et al, 2009).…”