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Electro-Olfactograms in Humans in Response to Ortho- and Retronasal Chemosensory Stimulation

Abstract

Aim

Ortho- and retronasal olfaction represent two aspects of a shared sensory system yet evoke different sensations. The differences between ortho- and retronasal olfaction have triggered a number of studies during the past years, which pointed towards a decreased sensitivity to odors presented through the retronasal olfactory pathway. Especially intensity was reported to be lower after retronasal olfactory stimulation. The aim of this study was to investigate how this compares to activation at the level of the olfactory epithelium in humans.

Methods

Trigeminal (CO2) and olfactory (H2S, phenylethyl alcohol) stimuli were presented ortho- and retronasally. Electro-olfactograms (EOG) in response to chemosensory stimulation were recorded in 10 participants (6 women, 4 men, mean age 23.4 years).

Results

Typical EOGs were demonstrable after either orthonasal or retronasal stimulation across the stimulus qualities. Overall, EOG amplitudes to retronasal stimulation were smaller when compared to those to orthonasal stimulation, but a significant difference was obtained only in phenylethyl alcohol (p = 0.048).

Conclusions

The present data indicate that the perceptual differences between ortho- and retronasal olfaction may start at the level of the olfactory epithelium. The data support the idea that the intensity of physically identical stimuli is lower after retronasal stimulation compared to orthonasal stimulus presentation for both olfactory and trigeminal stimuli.

Implications

The current electrophysiological results are in line with reported differences in psychophysical properties of retro- and orthonasal stimulations meaning that different sensations are elicit through these two channels although the same molecule is presented.

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Correspondence to Thomas Hummel.

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Funding

This study was funded by a grant from the Deutsche Forschungsgemeinschaft to TH (DFG HU441/18-1).

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The authors declare that they have no conflict of interest.

Ethical Approval

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.

Informed Consent

Informed consent was obtained from all individual participants included in the study.

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Hummel, T., Seo, HS., Pellegrino, R. et al. Electro-Olfactograms in Humans in Response to Ortho- and Retronasal Chemosensory Stimulation. Chem. Percept. 10, 114–118 (2017). https://doi.org/10.1007/s12078-016-9217-z

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  • DOI: https://doi.org/10.1007/s12078-016-9217-z

Keywords

  • Olfaction
  • Food
  • Olfactory receptors
  • Eating
  • Smell
  • Nose
  • Pharynx