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Updated: Aug 23, 2026

A Free-breathing fMRI Method to Study Human Olfactory Function
Published on: July 30, 2017
Near-infrared spectroscopy of the adult human olfactory cortex
Tadashi Ishimaru1, Tsuyoshi Yata, Kumiko Horikawa
1Department of Otolaryngology, Head and Neck Surgery, Nanto General Hospital, Nishitonami, Toyama, Japan. ishimaru-t@nanto-hp.jp
Objective:
Near-infrared spectroscopy (NIRS) is a non-invasive method for investigating activation of the human cortex. The applicability of NIRS to the olfactory cortex was investigated.
Material And Methods:
The relative oxy- and deoxy-hemoglobin levels of the orbito-frontal cortex during olfactory stimulation in healthy subjects were measured using NIRS.
Results:
When perfumed strips containing the odorants beta-phenyl ethyl alcohol, iso-valeric acid and gamma-undecalactone were presented, the oxy-hemoglobin level increased but the deoxy-hemoglobin level did not change. The increase in the oxy-hemoglobin level was observed bilaterally. A placebo perfumed strip did not elicit a change in the hemoglobin level. It was also observed that the odorant intensity affected the oxy-hemoglobin level. Although the orbito-frontal cortices seemed to be activated bilaterally during olfaction, the right cortex was activated to a greater extent than the left.
Conclusion:
NIRS appears to be an adequate method for investigating the human olfactory cortex.
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