Morphological changes in secondary, but not primary, sensory cortex in individuals with life-long olfactory sensory deprivation

Peter, Moa G.; Mårtensson, Gustav; Postma, Elbrich M.; Nordin, Love Engström; Westman, Eric; Boesveldt, Sanne; Lundström, Johan N.

doi:10.1016/j.neuroimage.2020.117005

Cited by 23 publications

(101 citation statements)

References 65 publications

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“…Patients with congenital anosmia, who had poorest olfactory function, showed an increased gray matter volume of the medial and superior OFC compared to the other patients. These results are in line with studies that found an increase in cortical thickness of the medial OFC 29 and increased gray matter volume in the medial orbital gyrus bilaterally 30 in patients with congenital anosmia compared to healthy controls. However, they contrast with Karstensen et al, who showed a reduced gray matter volume of the medial OFC in patients with congenital anosmia 28 .…”

Section: Discussionsupporting

confidence: 92%

“…Findings on morphology of the orbitofrontal cortex are conflicting. Frasnelli et al reported an increase of cortical thickness of the medial orbitofrontal cortex bilaterally, and Peter et al found increased gray matter volume in the medial orbital gyrus bilaterally 29 , 30 . In contrast, Karstensen et al found reduced gray matter volume in the left medial orbitofrontal cortex 28 .…”

Section: Introductionmentioning

confidence: 99%

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Investigating morphological changes in the brain in relation to etiology and duration of olfactory dysfunction with voxel-based morphometry

Postma

Smeets

Boek

et al. 2021

Sci Rep

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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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Section: Discussionsupporting

confidence: 92%

Section: Introductionmentioning

confidence: 99%

Investigating morphological changes in the brain in relation to etiology and duration of olfactory dysfunction with voxel-based morphometry

Postma

Smeets

Boek

et al. 2021

Sci Rep

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“…Nonetheless, on the other extreme of the time-spectra lie individuals who are born without a sense of smell and who can serve as a theoretical contrast to assess potential effects of time. In line with this assumption, and in contradiction with the present results, we recently showed that the piriform cortex in individuals with congenital anosmia did not differ from healthy controls in either gray matter volume, cortical thickness, or functional connectivity to olfactory-associated areas (Peter et al, 2021(Peter et al, , 2020; but see Frasnelli et al, 2013). Why there is more evidence of reorganization in primary olfactory regions in individuals with shorter olfactory sensory loss, here with an average of 14 months without olfactory inputs, than in individual with long-term sensory loss is not known.…”

Section: Discussioncontrasting

confidence: 80%

“…Most evidence of sensory loss-related neuroplasticity originates from the visual and auditory systems where significant effects are demonstrated in primary sensory processing areas (Fine and Park, 2018;Röder and Rösler, 2004). Studies assessing impact on primary olfactory cortex (piriform cortex) due to loss of the sense of smell (anosmia) have, in contrast, reported either minor (Frasnelli et al, 2013;Karstensen et al, 2018;Peng et al, 2013;Reichert and Schöpf, 2018) or indiscernible functional or morphological changes (Han et al, 2018(Han et al, , 2017Peter et al, 2021Peter et al, , 2020Yao et al, 2018). The vast majority of studies exploring neural impact of acquired visual and auditory sensory loss have focused on adult individuals that experienced their sensory loss early, often before their second year of life, and with many years without sensory function.…”

Section: Introductionmentioning

confidence: 99%

“…Combined with the fact that anosmia is our most common sensory loss, affecting an estimated full 5% of the population (Brämerson et al, 2004;Landis et al, 2004), and with the COVID-19 pandemic and its associated olfactory problems potentially significantly increasing these numbers even more (Iravani et al, 2020;Parma et al, 2020), anosmia is a good model to study the effects of intermediate or late-onset sensory loss on neural plasticity. For morphology, there is clear evidence of structural reorganization following anosmia in large part around the orbitofrontal cortex (Bitter et al, 2010;Han et al, 2017;Li et al, 2020;Peter et al, 2020;Yao et al, 2018) but also in areas outside what is commonly regarded as olfactory processing areas, such as the insula cortex (Han et al, 2018(Han et al, , 2017Peng et al, 2013;Yao et al, 2014). In contrast, few studies have explored effects of olfactory sensory loss on functional connectivity from the primary olfactory cortex, the piriform cortex, or functional processing within.…”

Section: Introductionmentioning

confidence: 99%

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Acquired olfactory loss alters functional connectivity and morphology

Iravani

Peter

Arshamian

et al. 2021

Preprint

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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, n=20) and matched healthy controls (n=23) 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 alters 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. No significantly stronger connectivity in healthy control participants were demonstrated. 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 and taste processing. These results demonstrate that recently acquired sensory loss alters both cerebral morphology within core olfactory areas and increase dynamic functional connectivity from olfactory cortex to cerebral areas processing multisensory integration.

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International consensus statement on allergy and rhinology: Olfaction

Patel

Holbrook

Turner

et al. 2022

Int Forum Allergy Rhinol

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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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Morphological changes in secondary, but not primary, sensory cortex in individuals with life-long olfactory sensory deprivation

Cited by 23 publications

References 65 publications

Investigating morphological changes in the brain in relation to etiology and duration of olfactory dysfunction with voxel-based morphometry

Investigating morphological changes in the brain in relation to etiology and duration of olfactory dysfunction with voxel-based morphometry

Acquired olfactory loss alters functional connectivity and morphology

International consensus statement on allergy and rhinology: Olfaction

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