Olfactory Co-Stimulation Influences Intranasal Somatosensory Perception

ABSTRACT Olfactory sensitivity is influenced by intranasal trigeminal sensation. For instance, sniffing is central to how humans and animals perceive odorants. Here, we investigated the influence of olfactory co-stimulation on the perception of intranasal somatosensory stimulation. In this study, twenty-two healthy human subjects, with normal olfactory function, performed a localization task for weak air-puff stimuli, in the presence or absence of a pure odorant, phenyl ethyl alcohol (PEA; rose odor). Visual cues were used to inform participants to briefly hold their breath while weak, poorly localizable, air-puffs and/or PEA were delivered to either nostril. Although PEA alone could not be localized, when accompanied by a weak air-puff in the ipsilateral nostril, localization accuracy significantly improved, relative to presentation of the air-puff without the odorant. The enhancement of localization was absent when the air-puff and PEA were presented to opposite nostril. Since ipsilateral but not contralateral co-stimulation with PEA increased the accuracy of weak air-puff localization, the results argue against a non-specific alerting effect of PEA. These findings suggest an interaction between the olfactory and somatosensory trigeminal systems.