Olfactory Training Affects the Correlation Between Brain Structure and Functional Connectivity

Overview

Journal Neuroradiol J

Publisher Sage Publications

Specialties Neurology
Radiology

Date 2024 Dec 3

PMID 39626165

Authors

Abolhasan Rezaeyan

Somayeh Asadi

Seyed Kamran Kamrava

Arash Zare-Sadeghi

Affiliations

Soon will be listed here.

Abstract

Purpose: and background: Neuroimaging studies have increasingly found functional connectivity (FC) changes and structural cortical abnormalities in patients with post-traumatic anosmia (PTA). Training and repeated exposure to odorants lead to enhanced olfactory capability. This study is conducted to investigate the correlations between FC and cortical thickness on the olfaction-related regions of the brain in PTA after olfactory training (OT).

Methods: Twenty-five PTA patients were randomly divided in three groups: (1) 9 control patients who did not receive any training, (2) 9 patients underwent classical OT by 4 fixed odors, and (3) 7 patients underwent modified OT coming across 4 sets of 4 different odors sequentially. Before and after the training period, all patients performed olfactory function tests, and magnetic resonance imaging (MRI). Sniffin' Sticks test was used to assess olfactory function. MRI data were analyzed using functional connectivity analysis and brain morphometry.

Results: Modified OT resulted in heightened activation in the medial orbitofrontal cortex and anterior cingulate cortex and increased FC between the piriform cortex (PIRC) and the caudate cortex. Conversely, classical OT induced increased activation in the insula cortex and greater FC between the PIRC and the pre-central gyrus. Furthermore, after OT, both training groups achieved significantly improved scores in the changes in brain connectivity associated with OT, which were attributable to anatomical measures.

Conclusions: This study demonstrates that intensive olfactory training can enhance functional connectivity, and this improvement correlates with structural changes in the brain's olfactory processing areas.

References

Stankewitz A, May A . Increased limbic and brainstem activity during migraine attacks following olfactory stimulation. Neurology. 2011; 77(5):476-82. DOI: 10.1212/WNL.0b013e318227e4a8. View

Moessnang C, Frank G, Bogdahn U, Winkler J, Greenlee M, Klucken J . Altered activation patterns within the olfactory network in Parkinson's disease. Cereb Cortex. 2010; 21(6):1246-53. DOI: 10.1093/cercor/bhq202. View

Howell J, Costanzo R, Reiter E . Head trauma and olfactory function. World J Otorhinolaryngol Head Neck Surg. 2018; 4(1):39-45. PMC: 6051255. DOI: 10.1016/j.wjorl.2018.02.001. View

Howard J, Gottfried J . Configural and elemental coding of natural odor mixture components in the human brain. Neuron. 2014; 84(4):857-69. PMC: 4254622. DOI: 10.1016/j.neuron.2014.10.012. View

Oleszkiewicz A, Schriever V, Croy I, Hahner A, Hummel T . Updated Sniffin' Sticks normative data based on an extended sample of 9139 subjects. Eur Arch Otorhinolaryngol. 2018; 276(3):719-728. PMC: 6411676. DOI: 10.1007/s00405-018-5248-1. View

Jenkinson M, Beckmann C, Behrens T, Woolrich M, Smith S . FSL. Neuroimage. 2011; 62(2):782-90. DOI: 10.1016/j.neuroimage.2011.09.015. View

Hosseini S, Kamrava S, Asadi S, Maleki S, Zare-Sadeghi A, Shakeri-Zadeh A . A multimodal MR-compatible olfactometer with real-time controlling capability. J Med Eng Technol. 2020; 44(6):317-323. DOI: 10.1080/03091902.2020.1791987. View

Ashburner J . A fast diffeomorphic image registration algorithm. Neuroimage. 2007; 38(1):95-113. DOI: 10.1016/j.neuroimage.2007.07.007. View

Zald D, Mattson D, Pardo J . Brain activity in ventromedial prefrontal cortex correlates with individual differences in negative affect. Proc Natl Acad Sci U S A. 2002; 99(4):2450-4. PMC: 122385. DOI: 10.1073/pnas.042457199. View

10.

Croy I, Schulz M, Blumrich A, Hummel C, Gerber J, Hummel T . Human olfactory lateralization requires trigeminal activation. Neuroimage. 2014; 98:289-95. DOI: 10.1016/j.neuroimage.2014.05.004. View

11.

Dahnke R, Yotter R, Gaser C . Cortical thickness and central surface estimation. Neuroimage. 2012; 65:336-48. DOI: 10.1016/j.neuroimage.2012.09.050. View

12.

Seubert J, Freiherr J, Djordjevic J, Lundstrom J . Statistical localization of human olfactory cortex. Neuroimage. 2012; 66:333-42. DOI: 10.1016/j.neuroimage.2012.10.030. View

13.

Vance D, Del Bene V, Kamath V, Frank J, Billings R, Cho D . Does Olfactory Training Improve Brain Function and Cognition? A Systematic Review. Neuropsychol Rev. 2023; 34(1):155-191. PMC: 9891899. DOI: 10.1007/s11065-022-09573-0. View

14.

Langdon C, Lehrer E, Berenguer J, Laxe S, Alobid I, Quinto L . Olfactory Training in Post-Traumatic Smell Impairment: Mild Improvement in Threshold Performances: Results from a Randomized Controlled Trial. J Neurotrauma. 2018; 35(22):2641-2652. DOI: 10.1089/neu.2017.5230. View

15.

Kollndorfer K, Fischmeister F, Kowalczyk K, Hoche E, Mueller C, Trattnig S . Olfactory training induces changes in regional functional connectivity in patients with long-term smell loss. Neuroimage Clin. 2015; 9:401-10. PMC: 4590718. DOI: 10.1016/j.nicl.2015.09.004. View

16.

Adam-Darque A, Grouiller F, Vasung L, Ha-Vinh Leuchter R, Pollien P, Lazeyras F . fMRI-based Neuronal Response to New Odorants in the Newborn Brain. Cereb Cortex. 2017; 28(8):2901-2907. DOI: 10.1093/cercor/bhx167. View

17.

Altundag A, Cayonu M, Kayabasoglu G, Salihoglu M, Tekeli H, Saglam O . Modified olfactory training in patients with postinfectious olfactory loss. Laryngoscope. 2015; 125(8):1763-6. DOI: 10.1002/lary.25245. View

18.

Hummel T, Rissom K, Reden J, Hahner A, Weidenbecher M, Huttenbrink K . Effects of olfactory training in patients with olfactory loss. Laryngoscope. 2009; 119(3):496-9. DOI: 10.1002/lary.20101. View

19.

Ashburner J, Friston K . Voxel-based morphometry--the methods. Neuroimage. 2000; 11(6 Pt 1):805-21. DOI: 10.1006/nimg.2000.0582. View

20.

Kollndorfer K, Reichert J, Braunsteiner J, Schopf V . Assessment of Olfactory Memory in Olfactory Dysfunction. Perception. 2017; 46(3-4):516-529. DOI: 10.1177/0301006616683201. View