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. 2021 Feb;278(2):379-387.
doi: 10.1007/s00405-020-06233-y. Epub 2020 Aug 14.

Individual variability of olfactory fMRI in normosmia and olfactory dysfunction

Zang Yunpeng #  1   2 , Pengfei Han #  3   4 , Akshita Joshi  3 , Thomas Hummel  3
Affiliations

Individual variability of olfactory fMRI in normosmia and olfactory dysfunction

Zang Yunpeng et al. Eur Arch Otorhinolaryngol. 2021 Feb.

Abstract

Purpose: The diagnosis of olfactory dysfunction is mainly based on psychophysical measurements. The aim of the current study was to investigate how well the olfactory functional magnetic resonance imaging (fMRI) can effectively distinguish between normosmic people and subjects with olfactory dysfunction.

Methods: Thirty-eight participants were recruited for the study. Group 1 consisted of 22 subjects with olfactory dysfunction (mean age = 44.3 years, SD = 18.6), and Group two consisted of 16 participants with normal olfactory function (mean age = 49.6 years, SD = 11.6). Olfactory functions were assessed in great detail for all participants, and brain activation in response to odorous stimulation was assessed using fMRI.

Results: The between-group comparison showed stronger odor induced brain activation of the primary olfactory area and the insular cortex among the normosmic group as compared to the dysosmic group. As indicated by the individual analysis, positive responses in the primary olfactory cortex were significantly higher in normosmic people (94%) than in subjects with olfactory dysfunction (41%). However, there was no association between individual fMRI parameters (including the percentage of BOLD signal change, activated cluster size and peak z value), and psychophysical olfactory test scores. Receiver operating characteristic analysis suggested the subjects could not be differentiated from normosmics based on their BOLD signal from the primary olfactory area, orbitofrontal cortex, or the insular cortex.

Conclusion: There are large inter-individual variabilities for odor-induced brain activation among normosmic subjects and subjects with olfactory dysfunction, due to this variation, at present it appears problematic to diagnose olfactory dysfunction on an individual level using fMRI.

Keywords: Individual variability; Objective diagnosis; Olfactory dysfunction; fMRI.

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Conflict of interest statement

This research received financial support by the Deutsche Forschungsgemeinschaft to TH (DFG HU411/18-1). All other authors declare that they have no conflict of interest.

Figures

Fig. 1
Fig. 1
fMRI block design paradigm, totally 12 times of repeated “Task-Air” cycles. The time for each task is 8 s, the total time for presenting air is 12 s, during the odorless presentation, the first 4 s are buffer time
Fig. 2
Fig. 2
The light blue regions stand for the selected ROIs template: POC, OFC and Insular
Fig. 3
Fig. 3
(a) fMRI in 3 dimensions from a normosmic subject, red region indicates the activated voxel clusters in the insular, green region indicates the activated voxel clusters in the POC. (b) fMRI in 3 dimensions from a subject with olfactory dysfunction, red region indicates the activated voxel clusters in the insular. Yellow circle is used to emphasize the activated voxel clusters
See this image and copyright information in PMC

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