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Peter MG, Darki F, Thunell E, Mårtensson G, Postma EM, Boesveldt S, Westman E, Lundström JN. Lifelong olfactory deprivation-dependent cortical reorganization restricted to orbitofrontal cortex. Hum Brain Mapp 2023; 44:6459-6470. [PMID: 37915233 PMCID: PMC10681638 DOI: 10.1002/hbm.26522] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2023] [Revised: 10/02/2023] [Accepted: 10/06/2023] [Indexed: 11/03/2023] Open
Abstract
Prolonged sensory deprivation has repeatedly been linked to cortical reorganization. We recently demonstrated that individuals with congenital anosmia (CA, complete olfactory deprivation since birth) have seemingly normal morphology in piriform (olfactory) cortex despite profound morphological deviations in the orbitofrontal cortex (OFC), a finding contradictory to both the known effects of blindness on visual cortex and to the sparse literature on brain morphology in anosmia. To establish whether these unexpected findings reflect the true brain morphology in CA, we first performed a direct replication of our previous study to determine if lack of results was due to a deviant control group, a confound in cross sectional studies. Individuals with CA (n = 30) were compared to age and sex matched controls (n = 30) using voxel- and surface-based morphometry. The replication results were near identical to the original study: bilateral clusters of group differences in the OFC, including CA atrophy around the olfactory sulci and volume increases in the medial orbital gyri. Importantly, no group differences in piriform cortex were detected. Subsequently, to assess any subtle patterns of group differences not detectable by our mass-univariate analysis, we explored the data from a multivariate perspective. Combining the newly collected data with data from the replicated study (CA = 49, control = 49), we performed support vector machine classification based on gray matter volume. In line with the mass-univariate analyses, the multivariate analysis could accurately differentiate between the groups in bilateral OFC, whereas the classification accuracy in piriform cortex was at chance level. Our results suggest that despite lifelong olfactory deprivation, piriform (olfactory) cortex is morphologically unaltered and the morphological deviations in CA are confined to the OFC.
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Affiliation(s)
- Moa G. Peter
- Department of Clinical Neuroscience, Karolinska InstitutetStockholmSweden
| | - Fahimeh Darki
- Department of Clinical Neuroscience, Karolinska InstitutetStockholmSweden
| | - Evelina Thunell
- Department of Clinical Neuroscience, Karolinska InstitutetStockholmSweden
| | - Gustav Mårtensson
- Department of Neurobiology, Care Sciences and SocietyKarolinska InstitutetStockholmSweden
| | - Elbrich M. Postma
- Smell and Taste Centre, Hospital Gelderse ValleiEdethe Netherlands
- Division of Human Nutrition and HealthWageningen UniversityWageningenthe Netherlands
| | - Sanne Boesveldt
- Division of Human Nutrition and HealthWageningen UniversityWageningenthe Netherlands
| | - Eric Westman
- Department of Neurobiology, Care Sciences and SocietyKarolinska InstitutetStockholmSweden
- Department of Neuroimaging, Centre for Neuroimaging Sciences, Institute of Psychiatry, Psychology and Neuroscience, King's College LondonLondonUK
| | - Johan N. Lundström
- Department of Clinical Neuroscience, Karolinska InstitutetStockholmSweden
- Monell Chemical Senses CenterPhiladelphiaPennsylvaniaUSA
- Stockholm University Brain Imaging CenterStockholm UniversityStockholmSweden
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Rezaeyan A, Asadi S, Kamrava SK, Zare-Sadeghi A. Brain structural analysis in patients with post-traumatic anosmia: Voxel-based and surface-based morphometry. J Neuroradiol 2023; 50:482-491. [PMID: 36610937 DOI: 10.1016/j.neurad.2022.11.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2021] [Revised: 11/13/2022] [Accepted: 11/15/2022] [Indexed: 01/07/2023]
Abstract
PURPOSE AND BACKGROUND Voxel-based morphometry (VBM) and surfaced-based morphometry (SBM) investigate the characteristics of gray matter (GM) in various diseases such as post-traumatic anosmia (PTA). This study uses SBM and VBM to examine neuroanatomical measurements of GM and its functional correlates in patients with PTA. METHODS MRI images and olfactory test results were collected from 39 PTA patients and 39 healthy controls. Sniffin' Sticks test was used to assess olfactory function. GM structure was analyzed using CAT12 and FreeSurfer, and olfactory bulb (OB) volume and olfactory sulcus (OS) depth were calculated using 3D-Slicer. RESULTS Anosmic patients showed lower scores in the Sniffin' Sticks olfactory test, as well as reduction of OB volume and OS depth compared to control subjects. In these patients, overlapping changes were found between the VBM and SBM findings in the areas with significant effects, in particular, orbitofrontal cortex, superior and middle frontal gyrus, superior and middle temporal gyrus, anterior cingulate cortex, and insular cortex. Using SBM, decreased cortical thickness clusters were located in inferior and superior parietal gyrus. Further analysis in the region of interest demonstrated correlations between the orbitofrontal cortex and odor threshold score as well as the middle frontal gyrus and smell loss duration. CONCLUSION These findings show that the morphological alterations in the OB, OS, and the central olfactory pathways might contribute to the pathogenic mechanism of olfactory dysfunction after head injury.
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Affiliation(s)
- Abolhasan Rezaeyan
- Noncommunicable Diseases Research Center, Fasa University of Medical Sciences, Fasa, Iran; Department of Medical Physics, Faculty of Medicine, Fasa University of Medical Sciences, Fasa, Iran
| | - Somayeh Asadi
- Department of Medical Physics, School of Medicine, Iran University of Medical Sciences, Tehran, Iran
| | - S Kamran Kamrava
- ENT and Head and Neck Research Center and Department, The Five Senses Institute, Iran University of Medical Sciences, Tehran, Iran
| | - Arash Zare-Sadeghi
- Department of Medical Physics, School of Medicine, Iran University of Medical Sciences, Tehran, Iran; ENT and Head and Neck Research Center and Department, The Five Senses Institute, Iran University of Medical Sciences, Tehran, Iran; Finetech in Medicine Research Center, Iran University of Medical Sciences, Tehran, Iran.
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Avnioglu S, Sahin C, Cankaya S, Ozen O, Dikici R, Yilmaz H, Velioglu HA, Yulug B. Decreased frontal and orbital volumes and increased cerebellar volumes in patients with anosmia Of Unknown origin: A subtle connection? J Psychiatr Res 2023; 160:86-92. [PMID: 36791532 DOI: 10.1016/j.jpsychires.2023.01.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/01/2022] [Revised: 01/03/2023] [Accepted: 01/09/2023] [Indexed: 01/13/2023]
Abstract
PURPOSE Neuroimaging studies have shown that anosmia is accompanied by a decreased olfactory bulb volume, yet little is known about alterations in cerebral and cerebellar lobule volumes. The purpose of this study was to investigate structural brain alterations in anosmic patients. METHODS Sixteen anosmic patients (mean age 42.62 ± 16.57 years; 6 women and 10 men) and 16 healthy controls (mean age 43.37 ± 18.98 years; 9 women and 7 men) were included in this retrospective study. All subjects who underwent magnetic resonance imaging scans were analyzed using VolBrain and voxel-based morphometry after olfactory testing. RESULTS Despite being statistically insignificant, analysis using VBM revealed greater gray matter (GM) and white matter in the anosmia group compared to the healthy subjects. However, decreased GM (p < 0.001) and increased cerebellar (p = 0.046) volumes were observed in the anosmic patients. CONCLUSIONS The study revealed structural brain alterations in specific areas beyond the olfactory bulb. Our results indicate that the cerebellum may play an exceptional role in the olfactory process and that this will be worth evaluating with further dynamic neuroimaging studies.
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Affiliation(s)
- Seda Avnioglu
- Alanya Alaaddin Keykubat University Faculty of Medicine, Department of Anatomy, Antalya, Turkey.
| | - Caner Sahin
- Alanya Alaaddin Keykubat University Faculty of Medicine, Department of Ear, Nose and Throat, Antalya, Turkey.
| | - Seyda Cankaya
- Alanya Alaaddin Keykubat University, Faculty of Medicine, Department of Neurology, Antalya, Turkey.
| | - Ozkan Ozen
- Alanya Alaaddin Keykubat University, Faculty of Medicine, Department of Radiology, Antalya, Turkey.
| | - Rumeysa Dikici
- Alanya Alaaddin Keykubat University Faculty of Medicine, Department of Anatomy, Antalya, Turkey.
| | - Halil Yilmaz
- Nevsehir Haci Bektas Veli University, Kozakli Vocational School, Department of Therapy and Rehabilitation, Nevsehir, Turkey.
| | - Halil Aziz Velioglu
- Science for Life Laboratory, Department of Women's and Children's Health, Karolinska Institute, Stockholm, Sweden.
| | - Burak Yulug
- Alanya Alaaddin Keykubat University, Faculty of Medicine, Department of Neurology, Antalya, Turkey.
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Kamath V, Senjem ML, Spychalla AJ, Chen H, Palta P, Mosley TH, Windham BG, Griswold M, Knopman DS, Gottesman RF, Jack CR, Sharrett AR, Schneider ALC. The Neuroanatomic Correlates of Olfactory Identification Impairment in Healthy Older Adults and in Persons with Mild Cognitive Impairment. J Alzheimers Dis 2022; 89:233-245. [PMID: 35871337 PMCID: PMC10134400 DOI: 10.3233/jad-220228] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
BACKGROUND Olfactory identification (OI) impairment appears early in the course of Alzheimer's disease dementia (AD), prior to detectable cognitive impairment. However, the neuroanatomical correlates of impaired OI in cognitively normal older adults (CN) and persons with mild cognitive impairment (MCI) are not fully understood. OBJECTIVE We examined the neuroanatomic correlates of OI impairment in older adults from the Atherosclerosis Risk in Communities Neurocognitive Study (ARIC-NCS). METHODS Our sample included 1,600 older adults without dementia who completed clinical assessment and structural brain imaging from 2011 to 2013. We characterized OI impairment using the 12-item Sniffin' Sticks odor identification test (score ≤6). We used voxel-based morphometry (VBM) and region of interest (ROI) analyses to examine the neuroanatomic correlates of impaired OI in CN and MCI, after adjusting for potential confounders. Analyses were also separately stratified by race and sex. RESULTS In CN, OI impairment was associated with smaller amygdala gray matter (GM) volume (p < 0.05). In MCI, OI impairment was associated with smaller GM volumes of the olfactory cortex, amygdala, entorhinal cortex, hippocampus, and insula (ps < 0.05). Differential associations were observed by sex in MCI; OI impairment was associated with lower insular GM volumes among men but not among women (p-interaction = 0.04). There were no meaningful interactions by race. CONCLUSION The brain regions associated with OI impairment in individuals without dementia are specifically those regions known to be the primary targets of AD pathogenic processes. These findings highlight the potential utility of olfactory assessment in the identification and stratification of older adults at risk for AD.
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Affiliation(s)
- Vidyulata Kamath
- Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Matthew L Senjem
- Department of Radiology, Mayo Clinic, Rochester, MN, USA.,Department of Information Technology, Mayo Clinic, Rochester, MN, USA
| | | | - Honglei Chen
- Department of Epidemiology and Biostatistics, Michigan State University, East Lansing, MI, USA
| | - Priya Palta
- Division of General Medicine, Department of Medicine, Columbia University Irving Medical Center, New York, NY, USA
| | - Thomas H Mosley
- The MIND Center, Department of Medicine, The University of Mississippi School of Medicine, Jackson, MI, USA
| | - B Gwen Windham
- The MIND Center, Department of Medicine, The University of Mississippi School of Medicine, Jackson, MI, USA
| | - Michael Griswold
- The MIND Center, Department of Medicine, The University of Mississippi School of Medicine, Jackson, MI, USA
| | | | - Rebecca F Gottesman
- National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA
| | | | - A Richey Sharrett
- Department of Epidemiology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, MD, USA
| | - Andrea L C Schneider
- Department of Neurology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA
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Gao X, Su B, Sun Z, Xu L, Wei Y, Wu D. Patterns of Gray and White Matter Volume Alterations in Patients With Post-Traumatic Anosmia: A Voxel-Based Morphometry Study. Front Neurol 2022; 13:690760. [PMID: 35860485 PMCID: PMC9289146 DOI: 10.3389/fneur.2022.690760] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2021] [Accepted: 06/13/2022] [Indexed: 11/13/2022] Open
Abstract
ObjectiveTraumatic brain injury is one of the major causes of human olfactory dysfunction and leads to brain structure alterations, mainly in the cortical olfactory regions. Our study aimed to investigate volume changes in the gray matter (GM) and white matter (WM) in patients with post-traumatic anosmia and then to explore the relationship between GM volume and olfactory function.MethodsEthics committee approved prospective studies which included 22 patients with post-traumatic anosmia and 18 age- and gender-matched healthy volunteers. Olfactory function was assessed using the Sniffin' Sticks. High-resolution 3-dimensional T1 MRIs of the participants were acquired on a 3T scanner and the data were collected for voxel-based morphometry (VBM) analysis. Furthermore, the GM and WM volumes of the whole brain regions were compared and correlated with olfactory function.ResultsThe analysis revealed significant GM volume reduction in the orbitofrontal cortex (OFC), gyrus rectus (GR), olfactory cortex, insula, parahippocampal, temporal pole, and cerebellum (all P < 0.001) in patients. Besides, WM volume loss was also found in the OFC, GR, and insula (all P < 0.001) in patients. All WM atrophy areas were connected to areas of GM volume loss spatially. Correlation analysis showed the olfactory scores were significantly positively correlated with the GM volume of the occipital cortex (P < 0.001, and PFWE < 0.05), while no significant correlation was found between the Sniffin' Sticks test scores and the WM volume in patients.ConclusionThe reduction of GM and WM volume in olfactory-related regions was responsible for olfactory dysfunction in post-traumatic patients. The occipital cortex may play a compensation mechanism to maintain the residual olfactory function. To our knowledge, we report here for the first time on white matter volume alterations specifically in post-traumatic patients with anosmia.
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Affiliation(s)
- Xing Gao
- Department of Otorhinolaryngology-Head and Neck Surgery, Children's Hospital, Capital Institute of Pediatrics, Beijing, China
| | - Baihan Su
- Department of Otolaryngology, Smell and Taste Center, Beijing Anzhen Hospital, Capital Medical University, Beijing, China
| | - Zhifu Sun
- Department of Otolaryngology, Smell and Taste Center, Beijing Anzhen Hospital, Capital Medical University, Beijing, China
| | - Lei Xu
- Department of Medical Imaging, Beijing Anzhen Hospital, Capital Medical University, Beijing, China
| | - Yongxiang Wei
- Department of Otorhinolaryngology-Head and Neck Surgery, Children's Hospital, Capital Institute of Pediatrics, Beijing, China
- *Correspondence: Yongxiang Wei
| | - Dawei Wu
- Department of Otorhinolaryngology-Head and Neck Surgery, Peking University Third Hospital, Beijing, China
- Dawei Wu
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Ginieis R, Abeywickrema S, Oey I, Keast RS, Peng M. Searching for individual multi-sensory fingerprints and their links with adiposity – New insights from meta-analyses and empirical data. Food Qual Prefer 2022; 99:104574. [DOI: 10.1016/j.foodqual.2022.104574] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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7
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Hura N, Yi JS, Lin SY, Roxbury CR. Magnetic Resonance Imaging as a Diagnostic and Research Tool in Patients with Olfactory Dysfunction: A Systematic Review. Am J Rhinol Allergy 2022; 36:668-683. [PMID: 35585698 DOI: 10.1177/19458924221096913] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
BACKGROUND Patients with acquired, idiopathic olfactory dysfunction (OD) commonly undergo magnetic resonance imaging (MRI) evaluation to rule out intracranial pathologies. This practice is highly debated given the expense of MRI relative to the probability of detecting a treatable lesion. This, combined with the increasing use of MRI in research to investigate the mechanisms underlying OD, provided the impetus for this comprehensive review. OBJECTIVE The purpose of this systematic review was to both assess the utility of MRI in diagnosis of idiopathic OD and to describe MRI findings among mixed OD etiologies to better understand its role as a research tool in this patient population. METHODS A literature search of PubMed, Embase, Cochrane, Web of Science, and Scopus for studies with original MRI data for patients with OD was completed. Studies exclusively investigating patients with neurocognitive deficits or those studying traumatic or congenital etiologies of OD were excluded. RESULTS From 1758 candidate articles, 33 studies were included. Four studies reviewed patients with idiopathic OD for structural pathologies on MRI, of which 17 of 372 (4.6%) patients had a potential central cause identified, and 3 (0.8%) had an olfactory meningioma or olfactory neuroblastoma. Fourteen studies (42.4%) reported significant correlation between olfactory bulb volume and olfactory outcomes, and 6 studies (18.8%) reported gray matter volume reduction, specifically in the orbitofrontal cortex, anterior cingulate cortex, insular cortex, parahippocampal, and piriform cortex areas, in patients with mixed OD etiologies. Functional MRI studies reported reduced brain activation and functional connectivity in olfactory network areas. CONCLUSION MRI uncommonly detects intracranial pathology in patients with idiopathic OD. Among patients with mixed OD etiologies, reduced olfactory bulb and gray matter volume are the most common abnormal findings on MRI. Further research is required to better understand the role of MRI and its cost-effectiveness in patients with acquired, idiopathic OD.
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Affiliation(s)
- Nanki Hura
- Department of Otolaryngology - Head and Neck Surgery, 1500The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.,Department of Otolaryngology - Head and Neck Surgery, 6595University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania, USA
| | - Julie S Yi
- Department of Otolaryngology - Head and Neck Surgery, 1500The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Sandra Y Lin
- Department of Otolaryngology - Head and Neck Surgery, 1500The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Christopher R Roxbury
- Section of Otolaryngology - Head and Neck Surgery, 21727The University of Chicago Medical Center, Chicago, Illinois, USA
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8
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Patel ZM, Holbrook EH, Turner JH, Adappa ND, Albers MW, Altundag A, Appenzeller S, Costanzo RM, Croy I, Davis GE, Dehgani-Mobaraki P, Doty RL, Duffy VB, Goldstein BJ, Gudis DA, Haehner A, Higgins TS, Hopkins C, Huart C, Hummel T, Jitaroon K, Kern RC, Khanwalkar AR, Kobayashi M, Kondo K, Lane AP, Lechner M, Leopold DA, Levy JM, Marmura MJ, Mclelland L, Miwa T, Moberg PJ, Mueller CA, Nigwekar SU, O'Brien EK, Paunescu TG, Pellegrino R, Philpott C, Pinto JM, Reiter ER, Roalf DR, Rowan NR, Schlosser RJ, Schwob J, Seiden AM, Smith TL, Soler ZM, Sowerby L, Tan BK, Thamboo A, Wrobel B, Yan CH. International consensus statement on allergy and rhinology: Olfaction. Int Forum Allergy Rhinol 2022; 12:327-680. [PMID: 35373533 DOI: 10.1002/alr.22929] [Citation(s) in RCA: 37] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2021] [Revised: 01/01/2021] [Accepted: 11/19/2021] [Indexed: 12/11/2022]
Abstract
BACKGROUND The literature regarding clinical olfaction, olfactory loss, and olfactory dysfunction has expanded rapidly over the past two decades, with an exponential rise in the past year. There is substantial variability in the quality of this literature and a need to consolidate and critically review the evidence. It is with that aim that we have gathered experts from around the world to produce this International Consensus on Allergy and Rhinology: Olfaction (ICAR:O). METHODS Using previously described methodology, specific topics were developed relating to olfaction. Each topic was assigned a literature review, evidence-based review, or evidence-based review with recommendations format as dictated by available evidence and scope within the ICAR:O document. Following iterative reviews of each topic, the ICAR:O document was integrated and reviewed by all authors for final consensus. RESULTS The ICAR:O document reviews nearly 100 separate topics within the realm of olfaction, including diagnosis, epidemiology, disease burden, diagnosis, testing, etiology, treatment, and associated pathologies. CONCLUSION This critical review of the existing clinical olfaction literature provides much needed insight and clarity into the evaluation, diagnosis, and treatment of patients with olfactory dysfunction, while also clearly delineating gaps in our knowledge and evidence base that we should investigate further.
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Affiliation(s)
- Zara M Patel
- Otolaryngology, Stanford University School of Medicine, Stanford, California, USA
| | - Eric H Holbrook
- Otolaryngology, Massachusetts Eye and Ear Infirmary, Boston, Massachusetts, USA
| | - Justin H Turner
- Otolaryngology, Vanderbilt School of Medicine, Nashville, Tennessee, USA
| | - Nithin D Adappa
- Otolaryngology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Mark W Albers
- Neurology, Harvard Medical School, Boston, Massachusetts, USA
| | - Aytug Altundag
- Otolaryngology, Biruni University School of Medicine, İstanbul, Turkey
| | - Simone Appenzeller
- Rheumatology, School of Medical Sciences, University of Campinas, São Paulo, Brazil
| | - Richard M Costanzo
- Physiology and Biophysics and Otolaryngology, Virginia Commonwealth University School of Medicine, Richmond, Virginia, USA
| | - Ilona Croy
- Psychology and Psychosomatic Medicine, TU Dresden, Dresden, Germany
| | - Greg E Davis
- Otolaryngology, Proliance Surgeons, Seattle and Puyallup, Washington, USA
| | - Puya Dehgani-Mobaraki
- Associazione Naso Sano, Umbria Regional Registry of Volunteer Activities, Corciano, Italy
| | - Richard L Doty
- Smell and Taste Center, Otolaryngology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Valerie B Duffy
- Allied Health Sciences, University of Connecticut, Storrs, Connecticut, USA
| | | | - David A Gudis
- Otolaryngology, Columbia University Irving Medical Center, New York, USA
| | - Antje Haehner
- Smell and Taste, Otolaryngology, TU Dresden, Dresden, Germany
| | - Thomas S Higgins
- Otolaryngology, University of Louisville School of Medicine, Louisville, Kentucky, USA
| | - Claire Hopkins
- Otolaryngology, Guy's and St. Thomas' Hospitals, London Bridge Hospital, London, UK
| | - Caroline Huart
- Otorhinolaryngology, Cliniques universitaires Saint-Luc, Institute of Neuroscience, Université catholgique de Louvain, Brussels, Belgium
| | - Thomas Hummel
- Smell and Taste, Otolaryngology, TU Dresden, Dresden, Germany
| | | | - Robert C Kern
- Otolaryngology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA
| | - Ashoke R Khanwalkar
- Otolaryngology, Stanford University School of Medicine, Stanford, California, USA
| | - Masayoshi Kobayashi
- Otorhinolaryngology-Head and Neck Surgery, Mie University Graduate School of Medicine, Mie, Japan
| | - Kenji Kondo
- Otolaryngology, Graduate School of Medicine, University of Tokyo, Tokyo, Japan
| | - Andrew P Lane
- Otolaryngology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Matt Lechner
- Otolaryngology, Barts Health and University College London, London, UK
| | - Donald A Leopold
- Otolaryngology, University of Vermont Medical Center, Burlington, Vermont, USA
| | - Joshua M Levy
- Otolaryngology, Emory University School of Medicine, Atlanta, Georgia, USA
| | - Michael J Marmura
- Neurology Thomas Jefferson University School of Medicine, Philadelphia, Pennsylvania, USA
| | - Lisha Mclelland
- Otolaryngology, University Hospitals Birmingham NHS Foundation Trust, Birmingham, UK
| | - Takaki Miwa
- Otolaryngology, Kanazawa Medical University, Ishikawa, Japan
| | - Paul J Moberg
- Psychiatry, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, USA
| | | | - Sagar U Nigwekar
- Division of Nephrology, Massachusetts General Hospital, Boston, Massachusetts, USA
| | - Erin K O'Brien
- Otolaryngology, Mayo Clinic Rochester, Rochester, Minnesota, USA
| | - Teodor G Paunescu
- Division of Nephrology, Massachusetts General Hospital, Boston, Massachusetts, USA
| | | | - Carl Philpott
- Otolaryngology, University of East Anglia, Norwich, UK
| | - Jayant M Pinto
- Otolaryngology, University of Chicago, Chicago, Illinois, USA
| | - Evan R Reiter
- Otolaryngology, Virginia Commonwealth University School of Medicine, Richmond, Virginia, USA
| | - David R Roalf
- Psychiatry, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, USA
| | - Nicholas R Rowan
- Otolaryngology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Rodney J Schlosser
- Otolaryngology, Medical University of South Carolina, Mt Pleasant, South Carolina, USA
| | - James Schwob
- Biomedical Sciences, Tufts University School of Medicine, Boston, Massachusetts, USA
| | - Allen M Seiden
- Otolaryngology, University of Cincinnati School of Medicine, Cincinnati, Ohio, USA
| | - Timothy L Smith
- Otolaryngology, Oregon Health and Sciences University, Portland, Oregon, USA
| | - Zachary M Soler
- Otolaryngology, Medical University of South Carolina, Mt Pleasant, South Carolina, USA
| | - Leigh Sowerby
- Otolaryngology, University of Western Ontario, London, Ontario, Canada
| | - Bruce K Tan
- Otolaryngology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA
| | - Andrew Thamboo
- Otolaryngology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Bozena Wrobel
- Otolaryngology, Keck School of Medicine, USC, Los Angeles, California, USA
| | - Carol H Yan
- Otolaryngology, School of Medicine, UCSD, La Jolla, California, USA
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9
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Lee S, Kim J, Kim BJ, Kim RY, Ha E, Kim S, Hong SN, Lyoo IK, Kim DW. Gray matter volume reduction in the emotional brain networks in adults with anosmia. J Neurosci Res 2022; 100:1321-1330. [PMID: 35240720 DOI: 10.1002/jnr.25037] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Revised: 01/24/2022] [Accepted: 02/12/2022] [Indexed: 11/10/2022]
Abstract
Loss of olfaction, or anosmia, frequently accompanies emotional dysfunctions, partly due to the overlapping brain regions between the olfactory and emotional processing centers. Here, we investigated whether anosmia was associated with gray matter volume alterations at a network level, and whether these alterations were related to the olfactory-specific quality of life (QOL) and depressive symptoms. Structural brain magnetic resonance imaging was acquired in 22 individuals with postinfectious or idiopathic anosmia (the anosmia group) and 30 age- and sex-matched controls (the control group). Using independent component analysis on the gray matter volumes, we identified 10 morphometric networks. The gray matter volumes of these networks were compared between the two groups. Olfactory-specific QOL and depressive symptoms were assessed by self-report questionnaires and clinician-administered interviews, respectively. The anosmia group showed lower gray matter volumes in the hippocampus-amygdala and the precuneus networks, relative to the control group. Lower gray matter volumes in the hippocampus-amygdala network were also linearly associated with lower olfactory-specific QOL and higher depressive symptom scores. These findings suggest a close relationship between anosmia and gray matter volume alterations in the emotional brain networks, albeit without determined causal relations.
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Affiliation(s)
- Suji Lee
- Ewha Brain Institute, Ewha W. University, Seoul, South Korea
| | - Jungyoon Kim
- Ewha Brain Institute, Ewha W. University, Seoul, South Korea.,Department of Brain and Cognitive Sciences, Ewha W. University, Seoul, South Korea
| | - Bong Jik Kim
- Department of Otorhinolaryngology-Head and Neck Surgery, Chungnam National University College of Medicine, Chungnam National University Sejong Hospital, Sejong, South Korea
| | - Rye Young Kim
- Ewha Brain Institute, Ewha W. University, Seoul, South Korea.,Graduate School of Pharmaceutical Sciences, Ewha W. University, Seoul, South Korea
| | - Eunji Ha
- Ewha Brain Institute, Ewha W. University, Seoul, South Korea
| | - Shinhye Kim
- Ewha Brain Institute, Ewha W. University, Seoul, South Korea.,Department of Brain and Cognitive Sciences, Ewha W. University, Seoul, South Korea
| | - Seung-No Hong
- Department of Otorhinolaryngology-Head and Neck Surgery, SMG-SNU Boramae Medical Center, Seoul National University College of Medicine, Seoul, South Korea
| | - In Kyoon Lyoo
- Ewha Brain Institute, Ewha W. University, Seoul, South Korea.,Department of Brain and Cognitive Sciences, Ewha W. University, Seoul, South Korea.,Graduate School of Pharmaceutical Sciences, Ewha W. University, Seoul, South Korea.,The Brain Institute and Department of Psychiatry, University of Utah, Salt Lake City, Utah, USA
| | - Dae Woo Kim
- Department of Otorhinolaryngology-Head and Neck Surgery, SMG-SNU Boramae Medical Center, Seoul National University College of Medicine, Seoul, South Korea
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10
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Manan HA, Yahya N, Han P, Hummel T. A systematic review of olfactory-related brain structural changes in patients with congenital or acquired anosmia. Brain Struct Funct 2022; 227:177-202. [PMID: 34635958 PMCID: PMC8505224 DOI: 10.1007/s00429-021-02397-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2021] [Accepted: 09/26/2021] [Indexed: 02/08/2023]
Abstract
Brain structural features of healthy individuals are associated with olfactory functions. However, due to the pathophysiological differences, congenital and acquired anosmia may exhibit different structural characteristics. A systematic review was undertaken to compare brain structural features between patients with congenital and acquired anosmia. A systematic search was conducted using PubMed/MEDLINE and Scopus electronic databases to identify eligible reports on anosmia and structural changes and reported according to PRISMA guidelines. Reports were extracted for information on demographics, psychophysical evaluation, and structural changes. Then, the report was systematically reviewed based on various aetiologies of anosmia in relation to (1) olfactory bulb, (2) olfactory sulcus, (3) grey matter (GM), and white matter (WM) changes. Twenty-eight published studies were identified. All studies reported consistent findings with strong associations between olfactory bulb volume and olfactory function across etiologies. However, the association of olfactory function with olfactory sulcus depth was inconsistent. The present study observed morphological variations in GM and WM volume in congenital and acquired anosmia. In acquired anosmia, reduced olfactory function is associated with reduced volumes and thickness involving the gyrus rectus, medial orbitofrontal cortex, anterior cingulate cortex, and cerebellum. These findings contrast to those observed in congenital anosmia, where a reduced olfactory function is associated with a larger volume and higher thickness in parts of the olfactory network, including the piriform cortex, orbitofrontal cortex, and insula. The present review proposes that the structural characteristics in congenital and acquired anosmia are altered differently. The mechanisms behind these changes are likely to be multifactorial and involve the interaction with the environment.
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Affiliation(s)
- Hanani Abdul Manan
- Smell and Taste Clinic, Department of Otorhinolaryngology, TU Dresden, Fetscherstrasse 74, 01307, Dresden, Germany.
- Makmal Pemprosesan Imej Kefungsian (Functional Image Processing Laboratory), Department of Radiology, University Kebangsaan Malaysia Medical Centre, Jalan Yaacob Latif, Bandar Tun Razak, Cheras, 56 000, Kuala Lumpur, Malaysia.
| | - Noorazrul Yahya
- Diagnostic Imaging and Radiotherapy Program, Faculty of Health Sciences, School of Diagnostic and Applied Health Sciences, Universiti Kebangsaan Malaysia, Jalan Raja Muda Abdul Aziz, 50300, Kuala Lumpur, Malaysia
| | - Pengfei Han
- The Key Laboratory of Cognition and Personality (Ministry of Education), Southwest University, Chongqing, China
- Faculty of Psychology, Southwest University, Chongqing, China
| | - Thomas Hummel
- Smell and Taste Clinic, Department of Otorhinolaryngology, TU Dresden, Fetscherstrasse 74, 01307, Dresden, Germany
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11
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Iravani B, Peter MG, Arshamian A, Olsson MJ, Hummel T, Kitzler HH, Lundström JN. Acquired olfactory loss alters functional connectivity and morphology. Sci Rep 2021; 11:16422. [PMID: 34385571 PMCID: PMC8361122 DOI: 10.1038/s41598-021-95968-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Accepted: 08/02/2021] [Indexed: 11/10/2022] Open
Abstract
Removing function from a developed and functional sensory system is known to alter both cerebral morphology and functional connections. To date, a majority of studies assessing sensory-dependent plasticity have focused on effects from either early onset or long-term sensory loss and little is known how the recent sensory loss affects the human brain. With the aim of determining how recent sensory loss affects cerebral morphology and functional connectivity, we assessed differences between individuals with acquired olfactory loss (duration 7-36 months) and matched healthy controls in their grey matter volume, using multivariate pattern analyses, and functional connectivity, using dynamic connectivity analyses, within and from the olfactory cortex. Our results demonstrate that acquired olfactory loss is associated with altered grey matter volume in, among others, posterior piriform cortex, a core olfactory processing area, as well as the inferior frontal gyrus and angular gyrus. In addition, compared to controls, individuals with acquired anosmia displayed significantly stronger dynamic functional connectivity from the posterior piriform cortex to, among others, the angular gyrus, a known multisensory integration area. When assessing differences in dynamic functional connectivity from the angular gyrus, individuals with acquired anosmia had stronger connectivity from the angular gyrus to areas primary responsible for basic visual processing. These results demonstrate that recently acquired sensory loss is associated with both changed cerebral morphology within core olfactory areas and increase dynamic functional connectivity from olfactory cortex to cerebral areas processing multisensory integration.
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Affiliation(s)
- Behzad Iravani
- Division of Psychology, Department of Clinical Neuroscience, Karolinska Institutet, Nobels väg 9, 171 77, Stockholm, Sweden
| | - Moa G Peter
- Division of Psychology, Department of Clinical Neuroscience, Karolinska Institutet, Nobels väg 9, 171 77, Stockholm, Sweden
| | - Artin Arshamian
- Division of Psychology, Department of Clinical Neuroscience, Karolinska Institutet, Nobels väg 9, 171 77, Stockholm, Sweden
| | - Mats J Olsson
- Division of Psychology, Department of Clinical Neuroscience, Karolinska Institutet, Nobels väg 9, 171 77, Stockholm, Sweden
| | - Thomas Hummel
- Department of Otorhinolaryngology, Smell and Taste Clinic, TU Dresden, Dresden, Germany
| | - Hagen H Kitzler
- Institute of Diagnostic and Interventional Neuroradiology, TU Dresden, Dresden, Germany
| | - Johan N Lundström
- Division of Psychology, Department of Clinical Neuroscience, Karolinska Institutet, Nobels väg 9, 171 77, Stockholm, Sweden. .,Monell Chemical Senses Center, Philadelphia, PA, USA. .,Department of Psychology, University of Pennsylvania, Philadelphia, PA, USA. .,Stockholm University Brain Imaging Centre, Stockholm University, Stockholm, Sweden.
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12
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Postma EM, Smeets PAM, Boek WM, Boesveldt S. Investigating morphological changes in the brain in relation to etiology and duration of olfactory dysfunction with voxel-based morphometry. Sci Rep 2021; 11:12704. [PMID: 34135435 DOI: 10.1038/s41598-021-92224-w] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2021] [Accepted: 05/24/2021] [Indexed: 02/05/2023] Open
Abstract
Olfactory loss (OL) affects up to 20% of the general population and is related to changes in olfaction-related brain regions. This study investigated the effect of etiology and duration of OL on gray matter volume (GMV) of these regions in 257 patients. Voxel-based morphometry was applied to measure GMV in brain regions of interest to test the effects of etiology and duration on regional GMV and the relation between olfactory function and regional GMV. Etiology of OL had a significant effect on GMV in clusters representing the gyrus rectus and orbitofrontal cortex (OFC), bilaterally. Patients with congenital anosmia had reduced GMV in the gyrus rectus and an increased OFC volume compared to patients with acquired OL. There was a significant association between volume of the left OFC and olfactory function. This implies that changes in GMV in patients with acquired OL are mainly reflected in the OFC and depend on olfactory function. Morphology of olfactory areas in the brain therefore seems to relate to olfactory function and the subsequent degree of exposure to olfactory input in patients with acquired OL. Differences in GMV in congenital anosmia are most likely due to the fact that patients were never able to smell.
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13
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Whitcroft KL, Noltus J, Andrews P, Hummel T. Sinonasal surgery alters brain structure and function: Neuroanatomical correlates of olfactory dysfunction. J Neurosci Res 2021; 99:2156-2171. [PMID: 34110641 DOI: 10.1002/jnr.24897] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2020] [Revised: 05/13/2021] [Accepted: 05/17/2021] [Indexed: 11/10/2022]
Abstract
Olfactory dysfunction (OD) is more common than hearing loss, partial blindness, or blindness and can have a significant impact on the quality of life. Moreover, unexplained OD is an early biomarker in neurodegenerative diseases and increases 5-year mortality risk. Structural alterations in olfactory eloquent brain regions may represent the neuroanatomical correlates of OD. Previous studies have demonstrated reduced gray matter (GM) volume in areas of presumed olfactory relevance in patients with OD. However, being cross-sectional in nature, these studies do not provide evidence of causality, for which longitudinal work is required. At present, however, longitudinal studies addressing olfactory structural plasticity are limited, both in number and methodological approach: to our knowledge, such work has not included parallel functional imaging to confirm the relevance of structural change. We therefore performed a longitudinal multimodal neuroimaging study investigating structural and functional plasticity in 24 patients undergoing surgical treatment for chronic rhinosinusitis, compared with 17 healthy controls. We demonstrated functionally significant structural plasticity within the orbitofrontal, anterior cingulate and insular cortices, and temporal poles in patients 3 months after surgery. Of interest, GM volume decreased in these regions, in association with increased psychophysical scores and BOLD signal. To our knowledge, this is the first study to demonstrate both structural and functional plasticity of the central olfactory networks, thereby confirming these areas as neuroanatomical correlates of olfactory function/dysfunction.
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Affiliation(s)
- Katherine L Whitcroft
- Department of Otorhinolaryngology, TU Dresden, Dresden, Germany.,UCL Ear Institute, University College London, London, UK.,Centre for the Study of the Senses, Institute of Philosophy, School of Advanced Study, University of London, London, UK.,Royal National Throat Nose and Ear Hospital, London, UK
| | - Jan Noltus
- Department of Otorhinolaryngology, TU Dresden, Dresden, Germany
| | - Peter Andrews
- UCL Ear Institute, University College London, London, UK.,Royal National Throat Nose and Ear Hospital, London, UK
| | - Thomas Hummel
- Department of Otorhinolaryngology, TU Dresden, Dresden, Germany
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14
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Rezaeyan A, Asadi S, Kamrava SK, Khoei S, Zare-Sadeghi A. Reorganizing brain structure through olfactory training in post-traumatic smell impairment: An MRI study. J Neuroradiol 2021; 49:333-342. [PMID: 33957160 DOI: 10.1016/j.neurad.2021.04.035] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2020] [Revised: 04/01/2021] [Accepted: 04/24/2021] [Indexed: 12/13/2022]
Abstract
PURPOSE AND BACKGROUND Post-traumatic olfactory dysfunction (PTOD), mostly caused by head injury, is thought to be associated with changes in the structure and function of the brain olfactory processing areas. Training and repeated exposure to odorants lead to enhanced olfactory capability. This study investigated the effects of a 16-weeks olfactory training (OT) on olfactory function and brain structure. METHODS Twenty-five patients with PTOD 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 structural magnetic resonance imaging (MRI). Sniffin' Sticks test was used to assess olfactory function. MRI data were analyzed using voxel-based morphometry and surface-based morphometry. RESULTS Both trained groups showed a considerable recovery of olfactory function, especially in odor identification. MRI data analysis revealed that the classical OT leads to increases in cortical thickness/density of several brain regions, including the right superior and middle frontal gyrus, and bilateral cerebellums. In addition, the modified OT yielded a lower extent of cortical measures in the right orbital frontal cortex and right insular. Following modified OT, a positive correlation was observed between the odor identification and the right orbital frontal cortex. CONCLUSION Both olfactory training methods can improve olfactory function and that the improvement is associated with changes in the structure of olfactory processing areas of the brain.
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Affiliation(s)
- Abolhasan Rezaeyan
- Department of Medical Physics, School of Medicine, Iran University of Medical Sciences (IUMS), Tehran, Iran
| | - Somayeh Asadi
- Department of Medical Physics, School of Medicine, Iran University of Medical Sciences (IUMS), Tehran, Iran
| | - S Kamran Kamrava
- ENT and Head & Neck Research Center and Department, The Five Senses Institute, Iran University of Medical Sciences (IUMS), Tehran, Iran
| | - Samideh Khoei
- Department of Medical Physics, School of Medicine, Iran University of Medical Sciences (IUMS), Tehran, Iran; Finetech in Medicine Research Center, Iran University of Medical Sciences (IUMS), Tehran, Iran
| | - Arash Zare-Sadeghi
- Department of Medical Physics, School of Medicine, Iran University of Medical Sciences (IUMS), Tehran, Iran; Finetech in Medicine Research Center, Iran University of Medical Sciences (IUMS), Tehran, Iran.
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15
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Abstract
‘Super smellers‘ are those individuals who show a heightened sense of smell. Data on the structural neuroanatomy of this phenomenon are still missing. A voxel-based morphometry study was conducted in order to compare gray matter volume (GMV) in specific brain regions of the olfactory network (piriform/entorhinal cortex, orbitofrontal cortex, insula, hippocampus) between 25 male ‘super smellers’ and 20 normosmic men. Participants were assigned to these groups based on their scores on a standardized olfactory performance test. Relative to normosmic men, ‘super smellers’ showed increased GMV in the anterior insula and in the hippocampus (dentate gyrus). These regions are crucial for the integration of olfactory information as well as odor learning and odor memory. Moreover, positive correlations between hippocampal volume and olfactory performance were detected in both groups. Future research should elaborate on how much of the observed neuroanatomical pattern of ‘super smellers’ is genetic and how much of it reflects experienced-based GMV increase.
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Affiliation(s)
- Albert Wabnegger
- Clinical Psychology, BioTechMed Graz, University of Graz, Universitätsplatz 2, 8010, Graz, Austria
| | - Carina Schlintl
- Clinical Psychology, BioTechMed Graz, University of Graz, Universitätsplatz 2, 8010, Graz, Austria
| | - Carina Höfler
- Clinical Psychology, BioTechMed Graz, University of Graz, Universitätsplatz 2, 8010, Graz, Austria
| | - Andreas Gremsl
- Clinical Psychology, BioTechMed Graz, University of Graz, Universitätsplatz 2, 8010, Graz, Austria
| | - Anne Schienle
- Clinical Psychology, BioTechMed Graz, University of Graz, Universitätsplatz 2, 8010, Graz, Austria.
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16
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Abstract
Olfactory dysfunctions affect a larger portion of population (up to 15% with partial olfactory loss, and 5% with complete olfactory loss) as compared to other sensory dysfunctions (e.g. auditory or visual) and have a negative impact on the life quality. The impairment of olfactory functions may happen at each stage of the olfactory system, from epithelium to cortex. Non-invasive neuroimaging techniques such as the magnetic resonance imaging (MRI) have advanced the understanding of the advent and progress of olfactory dysfunctions in humans. The current review summarizes recent MRI studies on human olfactory dysfunction to present an updated and comprehensive picture of the structural and functional alterations in the central olfactory system as a consequence of olfactory loss and regain. Furthermore, the review also highlights recent progress on optimizing the olfactory functional MRI as well as new approaches for data processing that are promising for future clinical practice.
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Affiliation(s)
- Pengfei Han
- Faculty of Psychology, Southwest University, Chongqing, China. .,Key Laboratory of Cognition and Personality, Ministry of Education, Southwest University, Chongqing, China. .,Department of Otorhinolaryngology, Interdisciplinary Center Smell and Taste, TU Dresden, Dresden, Germany.
| | - Yunpeng Zang
- Department of Otorhinolaryngology, Interdisciplinary Center Smell and Taste, TU Dresden, Dresden, Germany
| | - Joshi Akshita
- Department of Otorhinolaryngology, Interdisciplinary Center Smell and Taste, TU Dresden, Dresden, Germany
| | - Thomas Hummel
- Department of Otorhinolaryngology, Interdisciplinary Center Smell and Taste, TU Dresden, Dresden, Germany
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17
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Abstract
Abstract
The role of the cerebellum in the chemical senses is still poorly understood. This voxel-based morphometry (VBM) study investigated associations between gray matter volume (GMV) in subregions of the cerebellum and olfactory performance. VBM data from 48 men were analyzed. The participants were tested with a standardized olfactory test that measured olfactory threshold, discrimination, and identification ability. The investigated sample covered a wide range of olfactory performance, including individuals with a reduced sense of smell (anosmia and hyposmia) and normosmia. The computed regression analyses revealed a positive association between olfactory identification performance and GMV in lobule VI. This cerebellar subregion is involved in higher-order cognitive functions (language and memory), which are necessary prerequisites for correct odor labeling. Odor detection and discrimination were unrelated to cerebellar GMV.
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Affiliation(s)
- Albert Wabnegger
- Clinical Psychology, University of Graz, BioTechMed Graz, Universitätsplatz, Graz, Austria
| | - Anne Schienle
- Clinical Psychology, University of Graz, BioTechMed Graz, Universitätsplatz, Graz, Austria
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18
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Al Aïn S, Poupon D, Hétu S, Mercier N, Steffener J, Frasnelli J. Smell training improves olfactory function and alters brain structure. Neuroimage 2019; 189:45-54. [PMID: 30630079 DOI: 10.1016/j.neuroimage.2019.01.008] [Citation(s) in RCA: 52] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2018] [Revised: 12/10/2018] [Accepted: 01/04/2019] [Indexed: 11/25/2022] Open
Abstract
Training and repeated exposure to odorants leads to enhanced olfactory sensitivity. So far, the efficacy of intensive olfactory training on olfactory function in a healthy population and its underlying neurobiological basis remain poorly known. This study investigated the effects of a 6-week intensive and well-controlled olfactory training on olfactory function and brain structure/neuroplasticity. Thirty-six healthy young individuals were recruited and randomly distributed in three groups: (1) 12 participants underwent daily intensive olfactory training of at least 20 min that included an (a) odor intensity classification task, an (b) odor quality classification task and an (c) target odor detection task, (2) 12 participants underwent an equivalent visual control training, and (3) 12 control individuals did not participate in any training. Before and after the training period, all participants performed a series of olfactory tests and those from groups 1 and 2 underwent structural magnetic resonance (MR) imaging, from which we obtained measures such as cortical thickness and tissue density. Participants improved in the respectively trained tasks throughout the 6-weeks training period. Those who underwent olfactory training improved general olfactory function compared to control participants, especially in odor identification, thus showing intramodal transfer. Further, MR imaging analysis revealed that olfactory training led to increased cortical thickness in the right inferior frontal gyrus, the bilateral fusiform gyrus and the right entorhinal cortex. This research shows that intensive olfactory training can generally improve olfactory function and that this improvement is associated with changes in the structure of olfactory processing areas of the brain.
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Affiliation(s)
- Syrina Al Aïn
- Université du Québec à Trois-Rivières (UQTR), Trois-Rivières, QC, Canada
| | - Daphnée Poupon
- Université du Québec à Trois-Rivières (UQTR), Trois-Rivières, QC, Canada
| | | | - Noémie Mercier
- Université du Québec à Trois-Rivières (UQTR), Trois-Rivières, QC, Canada
| | | | - Johannes Frasnelli
- Université du Québec à Trois-Rivières (UQTR), Trois-Rivières, QC, Canada; Research Center, Sacré-Cœur Hospital, Montréal, QC, Canada.
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19
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Han P, Winkler N, Hummel C, Hähner A, Gerber J, Hummel T. Alterations of Brain Gray Matter Density and Olfactory Bulb Volume in Patients with Olfactory Loss after Traumatic Brain Injury. J Neurotrauma 2018; 35:2632-2640. [DOI: 10.1089/neu.2017.5393] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Affiliation(s)
- Pengfei Han
- Interdisciplinary Center on Smell and Taste, Department of Otorhinolaryngology, TU Dresden, Dresden, Germany
| | - Nicole Winkler
- Interdisciplinary Center on Smell and Taste, Department of Otorhinolaryngology, TU Dresden, Dresden, Germany
| | - Cornelia Hummel
- Interdisciplinary Center on Smell and Taste, Department of Otorhinolaryngology, TU Dresden, Dresden, Germany
| | - Antje Hähner
- Interdisciplinary Center on Smell and Taste, Department of Otorhinolaryngology, TU Dresden, Dresden, Germany
| | | | - Thomas Hummel
- Interdisciplinary Center on Smell and Taste, Department of Otorhinolaryngology, TU Dresden, Dresden, Germany
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20
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Abstract
The human brain sustains a slow but progressive decline in function as it ages and these changes are particularly profound in cognitive processing. A potential contributor to this deterioration is the gradual decline in the functioning of multiple sensory systems and the effects they have on areas of the brain that mediate cognitive function. In older adults, diminished capacity is typically observed in the visual, auditory, masticatory, olfactory, and motor systems, and these age-related declines are associated with both a decline in cognitive proficiency, and a loss of neurons in regions of the brain. We will review how the loss of hearing, vision, mastication skills, olfactory impairment, and motoric decline accompany cognitive loss, and how improved functioning of these systems may aid in the restoration of the cognitive abilities in older adults. The human brain appears to require a great deal of stimulation to maintain its cognitive efficacy as people age and environmental enrichment may aid in its maintenance and recovery.
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Affiliation(s)
- Michael Leon
- Department of Neurobiology and Behavior, University of California, Irvine, Irvine, CA, United States
| | - Cynthia Woo
- Department of Neurobiology and Behavior, University of California, Irvine, Irvine, CA, United States
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21
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Reichert JL, Postma EM, Smeets PAM, Boek WM, de Graaf K, Schöpf V, Boesveldt S. Severity of olfactory deficits is reflected in functional brain networks-An fMRI study. Hum Brain Mapp 2018; 39:3166-3177. [PMID: 29602198 DOI: 10.1002/hbm.24067] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2017] [Revised: 02/02/2018] [Accepted: 03/21/2018] [Indexed: 11/10/2022] Open
Abstract
Even though deficits in olfactory function affect a considerable part of the population, the neuronal basis of olfactory deficits remains scarcely investigated. To achieve a better understanding of how smell loss affects neural activation patterns and functional networks, we set out to investigate patients with olfactory dysfunction using functional magnetic resonance imaging (fMRI) and olfactory stimulation. We used patients' scores on a standardized olfactory test as continuous measure of olfactory function. 48 patients (mean olfactory threshold discrimination identification (TDI) score = 16.33, SD = 6.4, range 6 - 28.5) were investigated. Overall, patients showed piriform cortex activation during odor stimulation compared to pure sniffing. Group independent component analysis indicated that the recruitment of three networks during odor stimulation was correlated with olfactory function: a sensory processing network (including regions such as insula, thalamus and piriform cortex), a cerebellar network and an occipital network. Interestingly, recruitment of these networks during pure sniffing was related to olfactory function as well. Our results support previous findings that sniffing alone can activate olfactory regions. Extending this, we found that the severity of olfactory deficits is related to the extent to which neural networks are recruited both during olfactory stimulation and pure sniffing. This indicates that olfactory deficits are not only reflected in changes in specific olfactory areas but also in the recruitment of occipital and cerebellar networks. These findings pave the way for future investigations on whether characteristics of these networks might be of use for the prediction of disease prognosis or of treatment success.
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Affiliation(s)
- Johanna L Reichert
- Institute of Psychology, University of Graz, Graz, Austria.,BioTechMed, Graz, Austria
| | - Elbrich M Postma
- Division of Human Nutrition, Wageningen University, Wageningen, The Netherlands.,ENT Department, Hospital Gelderse Vallei, Ede, The Netherlands
| | - Paul A M Smeets
- Division of Human Nutrition, Wageningen University, Wageningen, The Netherlands.,Image Sciences Institute, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Wilbert M Boek
- ENT Department, Hospital Gelderse Vallei, Ede, The Netherlands
| | - Kees de Graaf
- Division of Human Nutrition, Wageningen University, Wageningen, The Netherlands
| | - Veronika Schöpf
- Institute of Psychology, University of Graz, Graz, Austria.,BioTechMed, Graz, Austria
| | - Sanne Boesveldt
- Division of Human Nutrition, Wageningen University, Wageningen, The Netherlands
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22
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Gellrich J, Han P, Manesse C, Betz A, Junghanns A, Raue C, Schriever VA, Hummel T. Brain volume changes in hyposmic patients before and after olfactory training. Laryngoscope 2017; 128:1531-1536. [PMID: 29238983 DOI: 10.1002/lary.27045] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2017] [Revised: 10/26/2017] [Accepted: 11/10/2017] [Indexed: 12/17/2022]
Abstract
OBJECTIVES/HYPOTHESIS Olfactory dysfunction is thought to be associated with reduced gray matter (GM) volume in olfactory-related brain areas. The aim of this study was to determine GM structural changes within olfactory-related regions of the brain in patients with smell loss due to upper respiratory tract infection (URTI) before and after olfactory rehabilitation. STUDY DESIGN Prospective intervention case-control study. METHODS Magnetic resonance imaging structural brain images were collected from 30 patients with smell loss due to URTI and 31 controls. Patients exposed themselves to odors (olfactory training [OT]) over 12 weeks and then were rescanned. Olfactory testing was performed using the validated Sniffin' Sticks test. GM was investigated with voxel-based morphometry. RESULTS GM volumes were found to be reduced in the limbic system and thalamus among pretraining patients compared to controls; in patients, OT was associated with a significant increase of GM volume in these two regions. The GM volume within other olfactory-related regions was not different between patients and controls. In addition, no relevant difference between the GM volume pre- and post-OT was observed in primary olfactory-related regions. CONCLUSIONS OT was associated with an increase in GM volume of the hippocampus and the thalamus, possibly pointing toward a strategy for more effective exploitation of olfactory signals based on a higher degree of attention toward odors and association of memories with olfactory input. LEVEL OF EVIDENCE 3b. Laryngoscope, 128:1531-1536, 2018.
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Affiliation(s)
- Janine Gellrich
- Department of Otorhinolaryngology.,Department of Neuropediatrics
| | | | | | | | | | - Claudia Raue
- Department of Neuroradiology, Technical University of Dresden, Dresden, Germany
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23
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Güllmar D, Seeliger T, Gudziol H, Teichgräber UK, Reichenbach JR, Guntinas-Lichius O, Bitter T. Improvement of olfactory function after sinus surgery correlates with white matter properties measured by diffusion tensor imaging. Neuroscience 2017; 360:190-196. [DOI: 10.1016/j.neuroscience.2017.07.070] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Revised: 07/27/2017] [Accepted: 07/28/2017] [Indexed: 11/17/2022]
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24
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Abstract
Anosmia and hyposmia, the inability or decreased ability to smell, is estimated to afflict 3-20% of the population. Risk of olfactory dysfunction increases with old age and may also result from chronic sinonasal diseases, severe head trauma, and upper respiratory infections, or neurodegenerative diseases. These disorders impair the ability to sense warning odors in foods and the environment, as well as hinder the quality of life related to social interactions, eating, and feelings of well-being. This article reports and extends on a clinical update commencing at the 2016 Association for Chemoreception Sciences annual meeting. Included were reports from: a patient perspective on losing the sense of smell with information on Fifth Sense, a nonprofit advocacy organization for patients with olfactory disorders; an otolaryngologist's review of clinical evaluation, diagnosis, and management/treatment of anosmia; and researchers' review of recent advances in potential anosmia treatments from fundamental science, in animal, cellular, or genetic models. As limited evidence-based treatments exist for anosmia, dissemination of information on anosmia-related health risks is needed. This could include feasible and useful screening measures for olfactory dysfunction, appropriate clinical evaluation, and patient counseling to avoid harm as well as manage health and quality of life with anosmia.
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Affiliation(s)
- Sanne Boesveldt
- Division of Human Nutrition, Wageningen University & Research, Wageningen, The Netherlands
| | - Elbrich M Postma
- Division of Human Nutrition, Wageningen University & Research, Wageningen, The Netherlands
- Smell and Taste Centre, Hospital Gelderse Vallei, PO Box 9025, 6710 HN Ede, The Netherlands
| | - Duncan Boak
- Fifth Sense, Sanderum House, 38 Oakley Road, Chino OX39 4TW, UK
| | - Antje Welge-Luessen
- Department of Otorhinolaryngology, University Hospital Basel, Petersgraben 4CH-4031 Basel, Switzerland
| | - Veronika Schöpf
- Institute of Psychology, University of Graz, Universitätsplatz 2, 8010 Graz, Austria
- BioTechMed Graz, Mozartgasse 12/II, 8010 Graz, Austria
| | - Joel D Mainland
- Monell Chemical Senses Center, 3500 Market Street, Philadelphia, PA 19104, USA
- Department of Neuroscience, University of Pennsylvania, 3400 Spruce Street, Philadelphia, PA 19104, USA
| | - Jeffrey Martens
- Department of Pharmacology & Therapeutics, University of Florida, Gainesville, FL, USA
| | - John Ngai
- Department of Molecular & Cell Biology, University of California, Berkeley, CA 94720-3200, USA
| | - Valerie B Duffy
- Department of Allied Health Sciences, University of Connecticut, 358 Mansfield Road, Box U-101 Storrs, CT 06269-2101, USA
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Micarelli A, Chiaravalloti A, Danieli R, Schillaci O, Alessandrini M. Cerebral metabolic changes related to clinical parameters in idiopathic anosmic patients during olfactory stimulation: a pilot investigation. Eur Arch Otorhinolaryngol 2017; 274:2649-55. [PMID: 28283789 DOI: 10.1007/s00405-017-4524-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2016] [Accepted: 02/25/2017] [Indexed: 10/20/2022]
Abstract
Idiopathic olfactory loss neural consequences have been studied especially by means of magnetic resonance imaging. Since other functional neuroimaging technique findings are lacking in the literature, present study used a validated 18F-2-fluoro-2-deoxy-D-glucose (FDG) functional positron emission tomography procedure under olfactory stimulation (OS) to assess brain changes in idiopathic anosmic patients (IAPs) in comparison with healthy subjects (HS). A voxel-based analysis between these groups was used to evaluate FDG uptake in the brain and perform a correlation analysis between metabolic responses and the Sniffin' stick test as well as intensity visuo-analogue scores and disease duration (DD). A significant relative decrease of glucose metabolism in the right and left frontal lobes, left insula, right parietal lobe, and left occipital, temporal and parietal lobes was found in IAPs during OS. The same condition resulted in a relative higher glucose metabolism in the right cerebellum in IAPs. Moreover, a negative correlation between DD and FDG uptake in the left temporo-parietal joint was found in IAPs. Such a correlation suggested a possible involvement of this area metabolic decrease in self-consciousness impairment, which is known to affect IAPs. Present preliminary functional results could be of interest to further deepen such neural impairments possibly useful for future perspective in pharmaceutical and rehabilitative protocols.
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26
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Abstract
For the visual and auditory senses, an array of studies has reported on neuronal reorganization processes after sensory loss. In contrast to this, neuroplasticity has been investigated only scarcely after loss of the olfactory sense. The present review focuses on the current extent of literature on structural and functional neuroplasticity effects after loss, with a focus on magnetic resonance imaging-based studies. We also include findings on the regain of the olfactory sense, for example after successful olfactory training. Existing studies indicate that widespread structural changes beyond the level of the olfactory bulb occur in the brain after loss of the olfactory sense. Moreover, on a functional level, loss of olfactory input not only entails changes in olfaction-related brain regions but also in the trigeminal system. Existing evidence should be strengthened by future longitudinal studies, a more thorough investigation of the neuronal consequences of congenital anosmia, and the application of state-of-the-art neuroimaging methods, such as connectivity analyses and joint analyses of brain structure and function.
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Affiliation(s)
- Johanna L Reichert
- 1 Institute of Psychology, University of Graz, Graz, Austria.,2 BioTechMed, Graz, Austria
| | - Veronika Schöpf
- 1 Institute of Psychology, University of Graz, Graz, Austria.,2 BioTechMed, Graz, Austria
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27
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Han P, Whitcroft KL, Fischer J, Gerber J, Cuevas M, Andrews P, Hummel T. Olfactory brain gray matter volume reduction in patients with chronic rhinosinusitis. Int Forum Allergy Rhinol 2017; 7:551-556. [DOI: 10.1002/alr.21922] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2016] [Revised: 01/03/2017] [Accepted: 01/10/2017] [Indexed: 01/19/2023]
Affiliation(s)
- Pengfei Han
- Smell & Taste Clinic, Department of Otorhinolaryngology; Technische Universität Dresden; Dresden Germany
- Department of Neuropediatrics; University Hospital Carl Gustav Carus; Dresden Germany
| | - Katherine L. Whitcroft
- Smell & Taste Clinic, Department of Otorhinolaryngology; Technische Universität Dresden; Dresden Germany
- UCL Ear Institute; London UK
| | - Jessica Fischer
- Smell & Taste Clinic, Department of Otorhinolaryngology; Technische Universität Dresden; Dresden Germany
| | - Johannes Gerber
- Department of Neuroradiology; Technische Universität Dresden; Dresden Germany
| | - Mandy Cuevas
- Smell & Taste Clinic, Department of Otorhinolaryngology; Technische Universität Dresden; Dresden Germany
| | | | - Thomas Hummel
- Smell & Taste Clinic, Department of Otorhinolaryngology; Technische Universität Dresden; Dresden Germany
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28
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Aronoff E, Hillyer R, Leon M. Environmental Enrichment Therapy for Autism: Outcomes with Increased Access. Neural Plast 2016; 2016:2734915. [PMID: 27721995 DOI: 10.1155/2016/2734915] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2016] [Revised: 06/20/2016] [Accepted: 08/23/2016] [Indexed: 01/24/2023] Open
Abstract
We have previously shown in two randomized clinical trials that environmental enrichment is capable of ameliorating symptoms of autism spectrum disorder (ASD), and in the present study, we determined whether this therapy could be effective under real-world circumstances. 1,002 children were given daily Sensory Enrichment Therapy, by their parents, using personalized therapy instructions given over the Internet. Parents were asked to assess the symptoms of their child every 2 weeks for up to 7 months. An intention-to-treat analysis showed significant overall gains for a wide range of symptoms in these children, including learning, memory, anxiety, attention span, motor skills, eating, sleeping, sensory processing, self-awareness, communication, social skills, and mood/autism behaviors. The children of compliant caregivers were more likely to experience a significant improvement in their symptoms. The treatment was effective across a wide age range and there was equal progress reported for males and females, for USA and international subjects, for those who paid and those who did not pay for the therapy, and for individuals at all levels of initial symptom severity. Environmental enrichment, delivered via an online system, therefore appears to be an effective, low-cost means of treating the symptoms of ASD.
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Hall JM, Powell J, Elbadawey MR, Birchall D, Zammit-Maempel I. Radiological appearances in olfactory dysfunction: pictorial review. J Laryngol Otol 2015; 129:529-34. [PMID: 26074255 DOI: 10.1017/S0022215115001097] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
BACKGROUND Olfactory dysfunction is a common condition that may in some cases require imaging to investigate a potential underlying cause. OBJECTIVES This review describes the anatomy of normal olfaction and illustrates the pathological substrates of olfactory dysfunction amenable to imaging.
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Kollndorfer K, Jakab A, Mueller C, Trattnig S, Schöpf V. Effects of chronic peripheral olfactory loss on functional brain networks. Neuroscience 2015; 310:589-99. [DOI: 10.1016/j.neuroscience.2015.09.045] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2015] [Revised: 09/16/2015] [Accepted: 09/18/2015] [Indexed: 01/18/2023]
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Cortese BM, McConnell PA, Froeliger B, Leslie K, Uhde TW. Burning odor-elicited anxiety in OEF/OIF combat veterans: Inverse relationship to gray matter volume in olfactory cortex. J Psychiatr Res 2015; 70:58-66. [PMID: 26424424 DOI: 10.1016/j.jpsychires.2015.08.015] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/04/2015] [Revised: 07/21/2015] [Accepted: 08/27/2015] [Indexed: 12/11/2022]
Abstract
Despite the anatomical overlap between the brain's fear/threat and olfactory systems, a very limited number of investigations have considered the role of odors and the central olfactory system in the pathophysiology of PTSD. The goal of the present study was to assess structural differences in primary and secondary olfactory cortex between combat veterans with and without PTSD (CV + PTSD, CV-PTSD, respectively). An additional goal was to determine the relationship between gray matter volume (GMV) in olfactory cortex and the distressing properties of burning-related odors. A region of interest voxel-based morphometric (VBM) approach was used to measure GMV in olfactory cortex in a well-characterized group of CV + PTSD (n = 20) and CV-PTSD (n = 25). Prior to the MRI exam, combat-related (i.e., burning rubber) and control odors were systematically sampled and rated according to their potential for eliciting PTSD symptoms. Results showed that CV + PTSD exhibited significantly reduced GMV in anterior piriform (primary olfactory) and orbitofrontal (secondary olfactory) cortices compared to CV-PTSD (both p < .01). For the entire group, GMV in bilateral anterior piriform cortex was inversely related to burning rubber odor-elicited memories of trauma (p < .05). GMV in orbitofrontal cortex was inversely related to both clinical and laboratory measures of PTSD symptoms (all p < .05). In addition to replicating an established inverse relationship between GMV in anxiety-associated brain structures and PTSD symptomatology, the present study extends those findings by being the first report of volumetric decreases in olfactory cortex that are inversely related to odor-elicited PTSD symptoms. Potential mechanisms underlying these findings are discussed.
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32
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Kollndorfer K, Kowalczyk K, Hoche E, Mueller CA, Pollak M, Trattnig S, Schöpf V. Recovery of olfactory function induces neuroplasticity effects in patients with smell loss. Neural Plast 2014; 2014:140419. [PMID: 25544900 DOI: 10.1155/2014/140419] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2014] [Accepted: 11/03/2014] [Indexed: 11/17/2022] Open
Abstract
The plasticity of brain function, especially reorganization after stroke or sensory loss, has been investigated extensively. Based upon its special characteristics, the olfactory system allows the investigation of functional networks in patients with smell loss, as it holds the unique ability to be activated by the sensorimotor act of sniffing, without the presentation of an odor. In the present study, subjects with chronic peripheral smell loss and healthy controls were investigated using functional magnetic resonance imaging (fMRI) to compare functional networks in one of the major olfactory areas before and after an olfactory training program. Data analysis revealed that olfactory training induced alterations in functional connectivity networks. Thus, olfactory training is capable of inducing neural reorganization processes. Furthermore, these findings provide evidence for the underlying neural mechanisms of olfactory training.
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