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dc.contributor.authorKjelvik, Grete
dc.contributor.authorEvensmoen, Hallvard Røe
dc.contributor.authorHummel, Thomas
dc.contributor.authorEngedal, Knut
dc.contributor.authorSelbæk, Geir
dc.contributor.authorSaltvedt, Ingvild
dc.contributor.authorHåberg, Asta
dc.identifier.citationFrontiers in Neurology. 2020, .en_US
dc.description.abstractBackground: Odor identification (OI) ability is a suggested early biomarker of Alzheimer’s disease. In this study, we investigated brain activity within the brain’s olfactory network associated with OI in patients with amnestic mild cognitive impairment (aMCI) and mild Alzheimer’s dementia (mAD) to uncover the neuronal basis of this impairment. Materials and Methods: Patients with aMCI (n = 11) or mAD (n = 6) and 28 healthy older adults underwent OI functional MRI (fMRI) at 3T, OI, odor discrimination, and cognitive tests and apolipoprotein-e4 (APOE4) genotyping. Eleven patients had cerebrospinal fluid (CSF) analyzed. Those with aMCI were followed for 2 years to examine conversion to dementia. Results: The aMCI/mAD group performed significantly worse on all OI tests and the odor discrimination test compared to controls. The aMCI/mAD group had reduced activation in the right anterior piriform cortex compared to the controls during OI fMRI [Gaussian random field (GRF) corrected cluster threshold, p < 0.05]. This group difference remained after correcting for age, sex education, and brain parenchymal fraction. This difference in piriform activity was driven primarily by differences in odor discrimination ability and to a lesser extent by OI ability. There was no group by odor discrimination/identification score interaction on brain activity. Across both groups, only odor discrimination score was significantly associated with brain activity located to the right piriform cortex. Brain activity during OI was not associated with Mini Mental Status Examination scores. At the group level, the aMCI/mAD group activated only the anterior insula, while the control group had significant activation within all regions of the olfactory network during OI fMRI. There was no association between brain activity during OI fMRI and total beta-amyloid levels in the CSF in the aMCI/mAD group. Conclusion: The OI impairment in aMCI/mAD patients is associated with significantly reduced activity in the piriform cortex compared to controls. Activation of downstream regions within the olfactory network is also significantly affected in the aMCI/mAD group, except the anterior insula, which is impinged late in the course of Alzheimer’s disease. OI tests thus reflect Alzheimer’s disease pathology in olfactory brain structures. Keywords: smell, olfaction, neurodegenaration, central nervous system (CNS), cognitionen_US
dc.publisherFrontiers Mediaen_US
dc.rightsNavngivelse 4.0 Internasjonal*
dc.titleThe Human Brain Representation of Odor Identification in Amnestic Mild Cognitive Impairment and Alzheimer's Dementia of Mild Degreeen_US
dc.typePeer revieweden_US
dc.typeJournal articleen_US
dc.source.journalFrontiers in Neurologyen_US
dc.description.localcodeCopyright © 2021 Kjelvik, Evensmoen, Hummel, Engedal, Selbæk, Saltvedt and Håberg. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.en_US

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Navngivelse 4.0 Internasjonal
Except where otherwise noted, this item's license is described as Navngivelse 4.0 Internasjonal