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. 2025 Jun;135(6):2089-2096.
doi: 10.1002/lary.32128. Epub 2025 Mar 28.

Functional but Not Structural Brain Changes After Olfactory Training in Women With COVID-19-Associated Olfactory Dysfunction

Zetian Li  1 , Julia Gebler  1 , Akshita Joshi  1 , Xinni Xu  1   2 , Divesh Thaploo  1 , Antje Hähner  1 , Vittoria Avaro  3 , Federico Calegari  3 , Thomas Hummel  1
Affiliations

Functional but Not Structural Brain Changes After Olfactory Training in Women With COVID-19-Associated Olfactory Dysfunction

Zetian Li et al. Laryngoscope. 2025 Jun.

Retraction in

Abstract

Background: Olfactory training (OT) is a recommended treatment for olfactory loss and has proven effective in clinical contexts, yet its effects on the central-nervous system remain unclear. This study aimed to investigate the functional and structural brain changes in patients with post-viral olfactory loss undergoing OT.

Methods: Twenty patients with post-viral olfactory loss and 19 healthy controls underwent OT for 3 months. All participants were assessed using the Sniffin' Sticks test and magnetic resonance imaging (MRI). Voxel-based morphometry and olfactory bulb volumetry were performed on structural images. Presenting an unpleasant odor, n-butanol, in a canonical block design, functional MRI was performed using whole-brain and region of interest analyses.

Results: Patients with post-viral olfactory loss showed significant improvement following OT. Enhanced functional activations were observed in the orbitofrontal cortex and parahippocampus, while OT had little or no effects on brain structures.

Conclusion: The present findings suggest that OT provides early perceptual and functional benefits, with structural changes potentially emerging later with extended training duration.

Keywords: COVID; MRI; olfactory loss; olfactory training; smell.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

FIGURE 1
FIGURE 1
Procedure of the current study in both control and patients with olfactory dysfunction cohorts. [Color figure can be viewed in the online issue, which is available at www.laryngoscope.com].
FIGURE 2
FIGURE 2
Olfactory improvement in Sniffin' Stick tests after olfactory training in patients and controls. **p < 0.01. [Color figure can be viewed in the online issue, which is available at www.laryngoscope.com].
FIGURE 3
FIGURE 3
Improved functional activation in the right orbitofrontal cortex from the whole brain analysis with significance level at uncorrected p < 0.001. [Color figure can be viewed in the online issue, which is available at www.laryngoscope.com].
See this image and copyright information in PMC

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