114 research outputs found
Normative data for subcortical regional volumes over the lifetime of the adult human brain
Normative data for volumetric estimates of brain structures are necessary to adequately assess
brain volume alterations in individuals with suspected neurological or psychiatric conditions.
Although many studies have described age and sex effects in healthy individuals for brain
morphometry assessed via magnetic resonance imaging, proper normative values allowing to
quantify potential brain abnormalities are needed. We developed norms for volumetric estimates
of subcortical brain regions based on cross-sectional magnetic resonance scans from 2790
healthy individuals aged 18 to 94 years using 23 samples provided by 21 independent research
groups. The segmentation was conducted using FreeSurfer, a widely used and freely available
automated segmentation software. Models predicting subcortical regional volumes of each
hemisphere were produced including age, sex, estimated total intracranial volume (eTIV),
scanner manufacturer, magnetic field strength, and interactions as predictors. The mean
explained variance by the models was 48%. For most regions, age, sex and eTIV predicted most
of the explained variance while manufacturer, magnetic field strength and interactions predicted
a limited amount. Estimates of the expected volumes of an individual based on its characteristics
and the scanner characteristics can be obtained using derived formulas. For a new individual,
significance test for volume abnormality, effect size and estimated percentage of the normative
population with a smaller volume can be obtained. Normative values were validated in
independent samples of healthy adults and in adults with Alzheimer's disease and schizophrenia
Patch-wise brain age longitudinal reliability (2020)
We recently introduced a patchâwise technique to estimate brain age from anatomical T1âweighted magnetic resonance imaging (T1w MRI) data. Here, we sought to assess its longitudinal reliability by leveraging a unique dataset of 99 longitudinal MRI scans from a single, cognitively healthy volunteer acquired over a period of 17âyears (aged 29â46âyears) at multiple sites. We built a robust patchâwise brain age estimation framework on the basis of 100 cognitively healthy individuals from the MindBoggle dataset (aged 19â61âyears) using the DesikanâKillianyâTourville atlas, then applied the model to the volunteer dataset. The results show a high prediction accuracy on the independent test set (R2 = .94, mean absolute error of 0.63âyears) and no statistically significant difference between manufacturers, suggesting that the patchâwise technique has high reliability and can be used for longitudinal multiâcentric studies
FreeSurfer cortical normative data for adults using Desikan-Killiany-Tourville and ex vivo protocols
We recently built normative data for FreeSurfer morphometric estimates of cortical regions using its default atlas parcellation (Desikan-Killiany or DK) according to individual and scanner characteristics. We aimed to produced similar normative values for Desikan-Killianny-Tourville (DKT) and ex vivo-based labeling protocols, as well as examine the differences between these three atlases. Surfaces, thicknesses, and volumes of cortical regions were produced using cross-sectional magnetic resonance scans from the same 2713 healthy individuals aged 18 to 94 years as used in the reported DK norms. Models predicting regional cortical estimates of each hemisphere were produced using age, sex, estimated intracranial volume (eTIV), scanner manufacturer and magnetic field strength (MFS) as predictors. The DKT and DK models generally included the same predictors and produced similar R2. Comparison between DK, DKT, ex vivo atlases normative cortical measures showed that the three protocols generally produced similar normative values
Brain atrophy and patch-based grading in individuals from the CIMA-Q study : a progressive continuum from subjective cognitive decline to AD
It has been proposed that individuals developing Alzheimerâs disease (AD) first experience a phase expressing subjective complaints of cognitive decline (SCD) without objective cognitive impairment. Using magnetic resonance imaging (MRI), our objective was to verify whether SNIPE probability grading, a new MRI analysis technique, would distinguish between clinical dementia stage of AD: Cognitively healthy controls without complaint (CH), SCD, mild cognitive impairment, and AD. SNIPE score in the hippocampus and entorhinal cortex was applied to anatomical T1-weighted MRI of 143 participants from the Consortium pour lâidentification prĂ©coce de la maladie Alzheimer - QuĂ©bec (CIMA-Q) study and compared to standard atrophy measures (volumes and cortical thicknesses). Compared to standard atrophy measures, SNIPE score appeared more sensitive to differentiate clinical AD since differences between groups reached a higher level of significance and larger effect sizes. However, no significant difference was observed between SCD and CH groups. Combining both types of measures did not improve between-group differences. Further studies using a combination of biomarkers beyond anatomical MRI might be needed to identify individuals with SCD who are on the beginning of the clinical continuum of AD
Effets des lésions dorsale et ventrale de l'hippocampe et des dommages collatéraux au subiculum dans des tùches de mémoires de travail spatiale chez le rat
Un rĂ©cent courant de recherches appuyĂ© par des donnĂ©es anatomiques et comportementales laisse prĂ©sager que la portion dorsale de lâhippocampe est responsable de la mĂ©moire spatiale alors que la portion ventrale joue un rĂŽle prĂ©dominant dans les comportements dâanxiĂ©tĂ© et de peur. LâexpĂ©rience prĂ©sentĂ©e dans ce mĂ©moire vise Ă Ă©valuer cette hypothĂšse en comparant un groupe de rats avec lĂ©sion de lâhippocampe dorsal, un groupe de rats avec lĂ©sion de lâhippocampe ventral et un groupe de rats contrĂŽles dans deux tĂąches de mĂ©moire de travail spatiale: la version classique du labyrinthe radial et la tĂąche de non appariement spatial dans le labyrinthe en T. Contrairement Ă la lĂ©sion ventrale, la lĂ©sion dorsale provoque un dĂ©ficit dâapprentissage dans les deux tĂąches. Toutefois, les analyses histologiques dĂ©montrent que câest un dommage involontaire au subiculum dorsal, combinĂ© Ă la lĂ©sion de lâhippocampe dorsal, qui est responsable du dĂ©ficit obtenu dans la tĂąche de non appariement spatial.Recently, evidences from anatomical and behavioral studies have suggested that the dorsal portion of the hippocampus assume spatial memory function where as the ventral portion of the hippocampus is involved in fear and anxiety-related behaviors. This experiment was aimed at testing this hypothesis. Two groups of rats, one with dorsal hippocampal lesions and one with ventral hippocampal lesions were compared to sham-operated controls in two spatial working memory tasks: the standard version of the radial arm maze and the nonmatching-to-place task in the T-maze. Performance of dorsal hippocampal lesioned rats was impaired in both tasks whereas ventral hippocampal lesions did not affect learning in either task. Further histological analyses showed that damage to th e nearby dorsal subiculum combined with the lesions to the dorsal hippocampus accounts for the deficit in the nonmatching-to-sample task
La contribution des occupations à l'identité des personnes qui vivent avec un trouble de la personnalité
Introduction : Les personnes qui vivent avec un trouble de la personnalité (TP) du groupe B rencontrent plusieurs difficultés fonctionnelles dans leurs activités de la vie quotidienne. Ces personnes composent aussi avec des perturbations marquées de leur identité qui influencent leur participation sociale et leur qualité de vie. La notion que l'engagement dans des occupations contribue à façonner l'identité est largement reconnue en ergothérapie. Malgré l'importance de ces enjeux sur le plan clinique, il n'y a eu aucune validation empirique chez cette clientÚle. Objectif : Cette étude vise à décrire comment les occupations et leurs sens aux yeux des personnes qui vivent avec un TP du groupe B façonnent leur identité. Méthodes : L'étude s'appuie sur un devis exploratoire de type mixte. Son volet qualitatif est descriptif interprétatif tandis que son volet quantitatif est descriptif. Dix adultes, ùgés entre 18 et 35 ans, ayant un TP du groupe B, ont individuellement partagé des récits sur la contribution de leurs occupations à leur identité. L'Engagement in meaningful activities survey (EMAS) et le Meaningful activity wants and needs assessment (MAWNA) ont été administrés de façon complémentaire pour optimiser la triangulation des données. Résultats : Les participants s'engagent souvent dans des occupations qui reflÚtent leur identité, mais ils soulignent avoir besoin de davantage de ce type d'expériences. Quatre cas de figure illustrent les contributions de leurs occupations à leur identité : 1) l'importance des occupations comme source d'affiliation qui influence la construction identitaire; 2) la contribution des occupations passées ou souhaitées; 3) la contribution idéalisée d'une seule occupation et 4) la contribution des occupations virtuelles. Conclusion : Ces résultats soulÚvent l'importance du contexte dans lequel se déroule les occupations et de l'expérience subjective pour mieux comprendre comment celles-ci contribuent à l'identité des personnes qui vivent avec un TP du groupe B.Introduction: People living with a cluster B personality disorder (PD) experience several functional difficulties in their everyday activities. These individuals also experience marked disruptions in their identity that affect their social participation and quality of life. The notion that engagement in occupations shapes one's identity is widely recognized in occupational therapy. Despite the clinical importance of these issues, there has been no empirical validation for this clientele. Objective: The purpose of this study was to explore how occupations and their meanings in the eyes of people living with group B PD shape their identity. Methods: This exploratory study used a mixed methods design. Its qualitative component is based on an interpretative descriptive design while the quantitative component is descriptive. Ten adults, aged between 18 and 35 years old, living with a cluster B PD shared narratives on occupations that are important for them and how their occupational experiences shape their vision of themselves. As a complement, the Engagement in meaningful activities survey (EMAS) and the Meaningful activity wants and needs assessment (MAWNA) were administered, to optimize the triangulation of the data. Results: Participants often engage in a variety of occupations that reflect who they are although they point out that they need more. Four cases illustrate the different contributions of occupation to participants' identity: 1) the importance of occupations as a source of social affiliation that influences identity construction; 2) the contribution of past and anticipated occupations; 3) the idealized contribution of a sole occupation and 4) the contribution of virtual occupations. Conclusion: These results highlight the importance of the context in which occupations take place and of subjective experiences to better understand how occupations contribute to the identity of people living with a cluster B PD
Multivariate consistency of resting-state fMRI connectivity maps acquired on a single individual over 2.5 years, 13 sites and 3 vendors
Studies using resting-state functional magnetic resonance imaging (rsfMRI) are increasingly collecting data at multiple sites in order to speed up recruitment or increase sample size. The main objective of this study was to assess the long-term consistency of rsfMRI connectivity maps derived at multiple sites and vendors using the Canadian Dementia Imaging Protocol (CDIP, www.cdip-pcid.ca). Nine to 10 min of functional BOLD images were acquired from an adult cognitively healthy volunteer scanned repeatedly at 13 Canadian sites on three scanner makes (General Electric, Philips and Siemens) over the course of 2.5 years. The consistency (spatial Pearsonâs correlation) of rsfMRI connectivity maps for seven canonical networks ranged from 0.3 to 0.8, with a negligible effect of time, but significant site and vendor effects. We noted systematic differences in data quality (i.e. head motion, number of useable time frames, temporal signal-to-noise ratio) across vendors, which may also confound some of these results, and could not be disentangled in this sample. We also pooled the long-term longitudinal data with a single-site, short-term (1 month) data sample acquired on 26 subjects (10 scans per subject), called HNU1. Using randomly selected pairs of scans from each subject, we quantified the ability of a data-driven unsupervised cluster analysis to match two scans of the same subjects. In this âfingerprintingâ experiment, we found that scans from the Canadian subject (Csub) could be matched with high accuracy intra-site (>95% for some networks), but that the accuracy decreased substantially for scans drawn from different sites and vendors, even falling outside of the range of accuracies observed in HNU1. Overall, our results demonstrate good multivariate stability of rsfMRI measures over several years, but substantial impact of scanning site and vendors. How detrimental these effects are will depend on the application, yet our results demonstrate that new methods for harmonizing multisite analysis represent an important area for future work
FreeSurfer subcortical normative data
This article contains a spreadsheet computing estimates of the
expected subcortical regional volumes of an individual based on its
characteristics and the scanner characteristics, in addition to supplementary results related to the article âNormative data for subcortical regional volumes over the lifetime of the adult human brainâ
(O. Potvin, A. Mouiha, L. Dieumegarde, S. Duchesne, 2016) [1] on
normative data for subcortical volumes. Data used to produce normative values was obtained by anatomical magnetic resonance
imaging from 2790 healthy individuals aged 18â94 years using 23
samples provided by 21 independent research groups. The segmentation was conducted using FreeSurfer. The spreadsheet includes
formulas in order to compute for a new individual, significance test
for volume abnormality, effect size and estimated percentage of the
normative population with a smaller volume while taking into
account age, sex, estimated intracranial volume (eTIV), and scanner
characteristics. Detailed R-squares of each predictor for all formula
are also reported as well as the difference of subcortical volumes
segmented by FreeSurfer on two different computer hardware setups
Radiological-pathological correlation in Alzheimer's disease : systematic review of antemortem MRI findings
Background: The standard method of ascertaining Alzheimerâs disease (AD) remains postmortem
assessment of amyloid plaques and neurofibrillary degeneration. Vascular pathology,
Lewy bodies, TDP-43, and hippocampal sclerosis are frequent comorbidities. There is therefore
a need for biomarkers that can assess these aetiologies and provide a diagnosis in vivo.
Objective: We conducted a systematic review of published radiological-pathological correlation
studies to determine the relationship between antemortem magnetic resonance imaging (MRI)
and neuropathological findings in AD.
Methods: We explored PubMed in June-July 2015 using âAlzheimerâs diseaseâ and
combinations of radiological and pathological terms. After exclusion following screening and
full-text assessment of the 552 extracted manuscripts, three others were added from their
reference list. In fine, we report results based on 27 articles.
Results: Independently of normal age-related brain atrophy, AD pathology is associated with
whole-brain and hippocampal atrophy and ventricular expansion as observed on T1-weighted
images. Moreover, cerebral amyloid angiopathy and cortical microinfarcts are also related to
brain volume loss in AD. Hippocampal sclerosis and TDP-43 are respectively associated with
hippocampal and medial temporal lobe atrophy. Brain volume loss correlates more strongly with
tangles than with any other pathological finding. White matter hyperintensities observed on
proton density, T2-weighted and FLAIR images are strongly related to vascular pathologies, but
are also associated with other histological changes such as gliosis or demyelination.
Discussion: Cerebral atrophy and white matter changes in the living brain reflect underlying
neuropathology and may be detectable using antemortem MRI. In vivo MRI may therefore be an
avenue for AD pathological staging
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