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Updated: Jun 22, 2026
10:42
A Free-breathing fMRI Method to Study Human Olfactory Function
Published on: July 30, 2017
Pupillary responses to intranasal trigeminal and olfactory stimulation
Christine B Schneider1, Tjalf Ziemssen, Benno Schuster
1Department of Neurology, University of Dresden Medical School, Dresden, Germany.
Summary
Pupillary responses to odors can indicate stimulus intensity and type, but not pleasantness. Pupil diameter changes reflect differences in olfactory and trigeminal stimulation strength.
Area of Science:
- Neuroscience
- Sensory Science
- Psychophysics
Background:
- Pupillary responses are involuntary physiological reactions.
- Investigating pupillary changes can offer insights into sensory processing.
Purpose of the Study:
- To determine if pupillary responses reflect odor intensity or hedonic tone.
- To differentiate between olfactory and trigeminal stimulation effects on pupil diameter.
Main Methods:
- 21 healthy subjects received intranasal stimuli (rose, lemon, rotten eggs, CO2) at varying concentrations via a computer-controlled olfactometer.
- Pupil diameter changes were measured ipsilaterally to stimulus presentation.
- Stimulus intensity and hedonic ratings were recorded.
Main Results:
- Both olfactory and trigeminal stimulation increased pupil diameter.
- Pupillary reaction latencies were fastest for high-concentration CO2 and slowest for low-concentration PEA.
- Response amplitudes were largest for high-concentration CO2 and smallest for PEA.
- Response latencies decreased with increasing stimulus intensity.
- No correlation was found between hedonic ratings and pupillary reactions.
Conclusions:
- Pupillary diameter changes indicate differences in stimulus modality and intensity.
- Pupillary responses do not reflect the pleasantness or unpleasantness of odors.
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