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Normal Olfactory Functional Connectivity Despite Life-Long Absence of Olfactory Experiences [article]

Moa G Peter, Peter Fransson, Gustav Martensson, Elbrich M Postma, Love Engstrom Nordin, Eric Westman, Sanne Boesveldt, Johan N Lundstrom
2020 bioRxiv   pre-print
Congenital blindness is associated with atypical morphology, and functional connectivity within and from, visual cortical regions; changes that are hypothesized to originate from a life-long absence of visual input and could be regarded as a general (re)organization principle of sensory cortices. Challenging this is the fact that individuals with congenital anosmia (life-long olfactory sensory loss) display little to no morphological changes in primary olfactory cortex. To determine whether
more » ... ctory input from birth is essential to establish and maintain normal functional connectivity in olfactory processing regions, akin to the visual system, we assessed differences in functional connectivity within olfactory cortex between individuals with congenital anosmia (n=33) and matched controls (n=34). Specifically, we assessed differences in connectivity between core olfactory processing regions as well as differences in regional homogeneity and homotopic connectivity within primary olfactory cortex. In contrast to congenital blindness, none of the analyses indicated atypical connectivity in individuals with congenital anosmia. In fact, post-hoc Bayesian analysis provided support for an absence of group differences. These results suggest that a lifelong absence of olfactory experience has limited impact on the functional connectivity in olfactory cortex, a finding that indicates a clear difference between sensory modalities in how sensory cortical regions develop.
doi:10.1101/2020.05.21.106161 fatcat:tia5tro4gbem3ifexsvmazz5pi

Towards harmonizing subtyping methods for neuroimaging studies in Alzheimer's disease [article]

Rosaleena Mohanty, Gustav Mårtensson, Konstantinos Poulakis, J-Sebastian Muehlboeck, Elena Rodriguez Vieitez, Konstantinos Chiotis, Michel J. Grothe, Agneta Nordberg, Daniel Ferreira, Eric Westman
2020 medRxiv   pre-print
Biological subtypes in Alzheimer's disease (AD), originally identified on neuropathological data, have been translated to in vivo biomarkers such as structural magnetic resonance imaging (sMRI) and positron emission tomography (PET), to disentangle the heterogeneity within AD. Although there is methodological variability across studies, comparable characteristics of subtypes are reported at the group level. In this study, we investigated whether group-level similarities translate to
more » ... evel agreement across subtyping methods, in a head-to-head context. Methods: We compared five previously published subtyping methods. Firstly, we validated the subtyping methods in 89 amyloid-beta positive (Aβ+) AD dementia patients (reference group: 70 Aβ- healthy individuals; HC) using sMRI. Secondly, we extended and applied the subtyping methods to 53 Aβ+ prodromal AD and 30 Aβ+ AD dementia patients (reference group: 200 Aβ- HC) using both sMRI and tau PET. Subtyping methods were implemented as outlined in each original study. Group-level and individual-level comparisons across methods were performed. Results: Each individual method was replicated and the proof-of-concept was established. All methods captured subtypes with similar patterns of demographic and clinical characteristics, and with similar maps of cortical thinning and tau PET uptake, at the group level. However, large disagreements were found at the individual level. Conclusions: Although characteristics of subtypes may be comparable at the group level, there is a large disagreement at the individual level across subtyping methods. Therefore, there is an urgent need for consensus and harmonization across subtyping methods. We call for establishment of an open benchmarking framework to overcome this problem.
doi:10.1101/2020.04.19.20064881 fatcat:tzn47yajmzgh5m6lku72j53zgm

AVRA: Automatic Visual Ratings of Atrophy from MRI images using Recurrent Convolutional Neural Networks [article]

Gustav Mårtensson, Daniel Ferreira, Lena Cavallin, J-Sebastian Muehlboeck, Lars-Olof Wahlund, Chunliang Wang, Eric Westman
2018 arXiv   pre-print
Quantifying the degree of atrophy is done clinically by neuroradiologists following established visual rating scales. For these assessments to be reliable the rater requires substantial training and experience, and even then the rating agreement between two radiologists is not perfect. We have developed a model we call AVRA (Automatic Visual Ratings of Atrophy) based on machine learning methods and trained on 2350 visual ratings made by an experienced neuroradiologist. It provides fast and
more » ... atic ratings for Scheltens' scale of medial temporal atrophy (MTA), the frontal subscale of Pasquier's Global Cortical Atrophy (GCA-F) scale, and Koedam's scale of Posterior Atrophy (PA). We demonstrate substantial inter-rater agreement between AVRA's and a neuroradiologist ratings with Cohen's weighted kappa values of κ_w = 0.74/0.72 (MTA left/right), κ_w = 0.62 (GCA-F) and κ_w = 0.74 (PA), with an inherent intra-rater agreement of κ_w = 1. We conclude that automatic visual ratings of atrophy can potentially have great clinical and scientific value, and aim to present AVRA as a freely available toolbox.
arXiv:1901.00418v1 fatcat:ymyalikb3fb2bndq4qgnw6ptvm

Divergent morphological changes within the orbitofrontal cortex in individuals with congenital olfactory sensory loss [article]

Moa G Peter, Gustav Mårtensson, Elbrich M Postma, Love Engström Nordin, Eric Westman, Sanne Boesveldt, Johan N Lundström
2019 bioRxiv   pre-print
Individuals with congenital sensory loss experience a total lack of input from the lost sense throughout development. This lack of input has been linked to altered brain morphology, mainly in cerebral areas normally devoted to the processing of the lost sense. In congenital olfactory sensory loss (anosmia), the only consistent morphological finding is a decreased depth of the olfactory sulci, linked to small or absent olfactory bulbs. Here, we aimed to establish whether congenital anosmia leads
more » ... to more widespread alterations by comparing gray matter volume, cortical thickness, and curvature between 34 individuals with isolated congenital anosmia and 34 matched controls. Individuals with anosmia demonstrated alterations in bilateral olfactory sulci, encompassing decreased sulcus depth, gray matter atrophy, and decreased curvature. They further demonstrated increased gray matter volume and cortical thickness in the medial orbital gyri; regions strongly linked to olfactory processing, sensory integration and value coding. No structural alterations in the primary olfactory (piriform) cortex were, however, demonstrated. Our results replicate and extend previous knowledge with findings of divergent morphological alterations in bilateral orbitofrontal cortex, indicating influences of different plastic processes and suggesting that a lifelong absence of sensory input does not necessarily lead to morphological alterations in primary sensory cortex.
doi:10.1101/760793 fatcat:hxlyy3do2rgazgxpggvxcd7qui

Normal Olfactory Functional Connectivity Despite Lifelong Absence of Olfactory Experiences

Moa G Peter, Peter Fransson, Gustav Mårtensson, Elbrich M Postma, Love Engström Nordin, Eric Westman, Sanne Boesveldt, Johan N Lundström
2020 Cerebral Cortex  
Congenital blindness is associated with atypical morphology and functional connectivity within and from visual cortical regions; changes that are hypothesized to originate from a lifelong absence of visual input and could be regarded as a general (re) organization principle of sensory cortices. Challenging this is the fact that individuals with congenital anosmia (lifelong olfactory sensory loss) display little to no morphological changes in the primary olfactory cortex. To determine whether
more » ... actory input from birth is essential to establish and maintain normal functional connectivity in olfactory processing regions, akin to the visual system, we assessed differences in functional connectivity within the olfactory cortex between individuals with congenital anosmia (n = 33) and matched controls (n = 33). Specifically, we assessed differences in connectivity between core olfactory processing regions as well as differences in regional homogeneity and homotopic connectivity within the primary olfactory cortex. In contrast to congenital blindness, none of the analyses indicated atypical connectivity in individuals with congenital anosmia. In fact, post-hoc Bayesian analysis provided support for an absence of group differences. These results suggest that a lifelong absence of olfactory experience has a limited impact on the functional connectivity in the olfactory cortex, a finding that indicates a clear difference between sensory modalities in how sensory cortical regions develop.
doi:10.1093/cercor/bhaa217 pmid:32810869 pmcid:PMC7727390 fatcat:ledtykykmzcofhtegdxip5qhnq

Stability of graph theoretical measures in structural brain networks in Alzheimer's disease

Gustav Mårtensson, Joana B. Pereira, Patrizia Mecocci, Bruno Vellas, Magda Tsolaki, Iwona Kłoszewska, Hilkka Soininen, Simon Lovestone, Andrew Simmons, Giovanni Volpe, Eric Westman
2018 Scientific Reports  
doi:10.1038/s41598-018-29927-0 pmid:30072774 pmcid:PMC6072788 fatcat:znwa2bynifch7jsjzvmxixgate

Towards harmonizing subtyping methods for PET and MRI studies of Alzheimer's disease

Rosaleena Mohanty, Gustav Mårtensson, Konstantinos Poulakis, Elena Rodriguez‐Vieitez, Michel Grothe, Agneta K Nordberg, Daniel Ferreira, Eric Westman
2020 Alzheimer's & Dementia  
Identification of biological subtypes in Alzheimer's disease (AD) has become a growing field for understanding the heterogeneity of the disease. Subtypes, originally identified by postmortem markers (Murray et al., 2011), have been translated to utilize in vivo biomarkers such as those based on structural magnetic resonance imaging (sMRI) and positron emission tomography (PET). While there exists methodological variability across studies, comparable characteristics are reported at grouplevel.
more » ... wever, the question that remains to be explored and the motivation for this study is: do group-level similarities translate to individual-level agreement across subtyping methods? Method: We compared five subtyping methods reported in previous studies in a twopart approach: (a) we validated the methods in 89 AD dementia patients (reference group: 70 healthy individuals; HC) from ADNI using sMRI only; (b) we extended and applied the methods to 30 AD dementia and 53 prodromal AD patients (reference group: 200 HC) from ADNI with concurrent sMRI and tau PET. All AD patients were Aβ positive while all HC were Aβ negative. Subtyping methods included four hypothesis-
doi:10.1002/alz.042807 fatcat:mxpg642bevhxzjfljmou4qv26q

AVRA: Automatic visual ratings of atrophy from MRI images using recurrent convolutional neural networks

Gustav Mårtensson, Daniel Ferreira, Lena Cavallin, J-Sebastian Muehlboeck, Lars-Olof Wahlund, Chunliang Wang, Eric Westman
2019 NeuroImage: Clinical  
Mårtensson, et al.  ...  Mårtensson, et al. NeuroImage: Clinical 23 (2019) 101872 the PA scores were based on slices in all three planes.  ... 
doi:10.1016/j.nicl.2019.101872 pmid:31154242 pmcid:PMC6545397 fatcat:wfn6galpx5egfmcuunobqu2h7a

Medial temporal atrophy in preclinical dementia: visual and automated assessment during six year follow-up

Gustav Mårtensson, Claes Håkansson, Joana B. Pereira, Sebastian Palmqvist, Oskar Hansson, Danielle Westen, Eric Westman
2020 NeuroImage: Clinical  
Mårtensson, et al. NeuroImage: Clinical 27 (2020) 102310 Gustav Mårtensson: Conceptualization, Methodology, Formal analysis, Investigation, Writing -original draft, Visualization, Data curation.  ...  Mårtensson, et al. NeuroImage: Clinical 27 (2020) 102310 sample distribution.  ... 
doi:10.1016/j.nicl.2020.102310 pmid:32580125 pmcid:PMC7317671 fatcat:snutgv3x4bfktn7xz6es33stje

Inter-modality assessment of medial temporal lobe atrophy in a non-demented population: application of a visual rating scale template across radiologists with varying clinical experience

Claes Håkansson, Ashkan Tamaddon, Henrik Andersson, Gustav Torisson, Gustav Mårtensson, My Truong, Mårten Annertz, Elisabet Londos, Isabella M. Björkman-Burtscher, Oskar Hansson, Danielle van Westen
2021 European Radiology  
All raters had access to an MTA template (published by Mårtensson et al in [18] ) during ratings but were given no further training. Raters were blinded to all clinical information.  ...  A previous study by Mårtensson et al has shown that differences in rating styles result in low agreement between experienced radiologists even when they are strongly correlated compared to volumetry [  ... 
doi:10.1007/s00330-021-08177-1 pmid:34328536 pmcid:PMC8794965 fatcat:2znxbgzvofcvvdhfr6gshank2e

Seeing beyond your nose? the effects of lifelong olfactory sensory deprivation on cerebral audio-visual integration

Moa G. Peter, Gustav Mårtensson, Elbrich M. Postma, Love Engström Nordin, Eric Westman, Sanne Boesveldt, Johan N. Lundström
2021 Neuroscience  
Lifelong auditory and visual sensory deprivation have been demonstrated to alter both perceptual acuity and the neural processing of remaining senses. Recently, it was demonstrated that individuals with anosmia, i.e. complete olfactory sensory deprivation, displayed enhanced multisensory integration performance. Whether this ability is due to a reorganization of olfactory processing regions to focus on cross-modal multisensory information or whether it is due to enhanced processing within
more » ... ensory integration regions is not known. To dissociate these two outcomes, we investigated the neural processing of dynamic audio-visual stimuli in individuals with congenital anosmia and matched controls (both groups, n = 33) using functional magnetic resonance imaging. Specifically, we assessed whether the previously demonstrated multisensory enhancement is related to cross-modal processing of multisensory stimuli in olfactory associated regions, the piriform and olfactory orbitofrontal cortices, or enhanced multisensory processing in established multisensory integration regions, the superior temporal and intraparietal sulci. No significant group differences were found in the a priori hypothesized regions using region of interest analyses. However, exploratory whole-brain analysis suggested higher activation related to multisensory integration within the posterior superior temporal sulcus, in close proximity to the multisensory region of interest, in individuals with congenital anosmia. No group differences were demonstrated in olfactory associated regions. Although results were outside our hypothesized regions, combined, they tentatively suggest that enhanced processing of audio-visual stimuli in individuals with congenital anosmia may be mediated by multisensory, and not primary sensory, cerebral regions.
doi:10.1016/j.neuroscience.2021.07.017 pmid:34311017 fatcat:xaaju5oudbgp3id2w5qyss4a5i

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

Moa G. Peter, Gustav Mårtensson, Elbrich M. Postma, Love Engström Nordin, Eric Westman, Sanne Boesveldt, Johan N. Lundström
2020 NeuroImage  
Gustav Mårtensson: Software, Formal analysis, Investigation, Writing -review & editing. Elbrich M. Postma: Investigation, Resources, Writing -review & editing.  ... 
doi:10.1016/j.neuroimage.2020.117005 pmid:32485304 fatcat:bxiujw362vgdjcty7qmniikpli

A Case Study of Muniicipal Solid Waste Management in Nepal Compared to the Situation in the European Union and Sweden

Gustav Larsson, Jakob Sahlén, Lennart Mårtensson, Sanjay Nath Khanal
2017 Linnaeus Eco-Tech  
Nepal, situated in the Himalayan belt has a rapidly growing population together with high urbanisation rate. These factors are currently causing problems connected to municipal solid waste (MSW). E.g. leakage of hazardous substances to soil and surrounding aquatic systems, spread of odour and naturally unfamiliar materials to natural biotopes, all of which generate environmental damage and health problems. There are certain differences in waste generation and waste composition between urban
more » ... s of Nepal. In order to retrieve a broad picture of the current waste management situation, three population differentiated municipalities in different areas of the country were investigated. Studies of the MSW regarding composition and generation were conducted. Moreover, waste management in Nepal was compared with the basic waste management in the European Union (EU) and Sweden. Landfill sites (LFS) in Ghorahi Municipality, Pokhara Sub-metropolitan City and Kathmandu Metropolitan City were studied. Our studies show differences in waste composition, generation and management between the three locations. The differences are somewhat interconnected with population size and tourism. Cities with higher population and more tourism tend to have a higher generation and more diverse MSW. Nevertheless, the urban areas of Nepal are very much in need of a more structured waste management system, a system more alike the waste management of EU. Apart from structural problems, there are attitude and behavioural issues that needs to be dealt with. Further studies regarding social patterns, attitude and behaviour, as well as the economic flow of MSW, needs to be conducted in order to retrieve an even broader picture and understand important underlying issues.
doi:10.15626/eco-tech.2010.046 fatcat:sgetf74vxvc63m4yo5yzjjnl6a

Inter-Cohort Validation of SuStaIn Model for Alzheimer's Disease

Damiano Archetti, Alexandra L. Young, Neil P. Oxtoby, Daniel Ferreira, Gustav Mårtensson, Eric Westman, Daniel C. Alexander, Giovanni B. Frisoni, Alberto Redolfi, for Alzheimer's Disease Neuroimaging Initiative and EuroPOND Consortium
2021 Frontiers in Big Data  
All the visual ratings were computed automatically by means of the Automatic Visual Ratings of Atrophy (AVRA) tool (Mårtensson et al., 2019) .  ...  Oxtoby, n.oxtoby@ucl.ac.uk; Daniel Ferreira, daniel.ferreira.padilla@ki.se; Gustav Mårtensson, gustav.martensson@ki.se; Eric Westman, eric.westman@ki.se; Daniel C.  ... 
doi:10.3389/fdata.2021.661110 pmid:34095821 pmcid:PMC8173213 fatcat:e4zx7jbhrvh2bcb6ycg6gat2zu

Atrophy of the Posterior Subiculum Is Associated with Memory Impairment, Tau- and Aβ Pathology in Non-demented Individuals

Olof Lindberg, Gustav Mårtensson, Erik Stomrud, Sebastian Palmqvist, Lars-Olof Wahlund, Eric Westman, Oskar Hansson
2017 Frontiers in Aging Neuroscience  
Copyright © 2017 Lindberg, Mårtensson, Stomrud, Palmqvist, Wahlund, Westman and Hansson.  ... 
doi:10.3389/fnagi.2017.00306 pmid:28979205 pmcid:PMC5611434 fatcat:l6bdcsaw75bqthze4ennm7dnze
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