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Updated: Jun 23, 2026
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A Free-breathing fMRI Method to Study Human Olfactory Function
Published on: July 30, 2017
Olfactory psychometric functions for homologous 2-ketones
J Enrique Cometto-Muñiz1, Michael H Abraham
1Department of Surgery (Otolaryngology), University of California, San Diego, La Jolla, CA 92093-0957, USA. ecometto@ucsd.edu
Behavioural Brain Research
|May 12, 2009
Summary
Human odor detection thresholds for ketones like acetone show increased sensitivity with longer carbon chains up to heptanone. These findings establish lower odor detection thresholds (ODTs) than previously reported.
Area of Science:
- Olfactory science
- Psychophysics
- Neuroscience
Background:
- Understanding human odor perception requires precise measurement of odor detection thresholds (ODTs).
- Previous studies on homologous ketones provide a basis for comparison, but absolute ODTs vary.
- Odorant concentration and presentation method (vapor vs. liquid) significantly impact measured responses.
Purpose of the Study:
- To measure concentration-odor detection functions for a series of homologous ketones.
- To determine the odor detection thresholds (ODTs) for propanone (acetone), 2-pentanone, 2-heptanone, and 2-nonanone.
- To compare human behavioral ODTs with cellular-level responses in mice.
Main Methods:
- Used an 8-channel air-dilution olfactometer for controlled vapor presentation.
- Employed a forced-choice procedure with gas chromatography for quantification.
- Recruited normosmic, nonsmoking young adults (17-22 per compound).
Main Results:
- Sigmoid (logistic) equations accurately fitted both group and individual odor functions.
- Odor sensitivity increased from acetone to 2-heptanone, plateauing for 2-nonanone.
- Obtained ODTs were consistently lower than previously reported values, with interindividual variability around one order of magnitude.
Conclusions:
- Human behavioral odor functions can be measured at vapor concentrations significantly lower than those used in cellular studies.
- Comparisons between vapor and liquid phase odorant concentrations are crucial for understanding olfactory potency across neural levels.
- The study provides precise, low-concentration ODTs for key ketones, refining our understanding of olfactory sensitivity.
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