Neurobiology of aging
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Neurobiology of aging · Feb 2018
Multimodal MRI quantification of the common neurostructural bases within the FTD-ALS continuum.
The continuum hypothesis linking the behavioral variant of frontotemporal dementia (bvFTD) and amyotrophic lateral sclerosis (ALS) is supported by clinical, pathological, genetic, and neuroimaging evidence. In the present multimodal magnetic resonance study, we characterized the site and extent of shared neurostructural changes in gray and white matter in 20 bvFTD and 19 ALS patients without dementia. ⋯ The quantification of gray and white matter damage within the areas of shared alterations highlighted a higher degree of atrophy in orbitofrontal and frontomedial regions in patients with more severe executive and/or behavioral symptoms, and a higher degree of degeneration in the motor pathway in patients with more severe motor neuron disorders. Our finding provides additional evidence confirming the FTD-ALS continuum hypothesis and supports the notion of a bimodal but convergent pattern of neurostructural changes characterizing bvFTD and ALS.
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Neurobiology of aging · Feb 2018
Patterns of gray matter atrophy in genetic frontotemporal dementia: results from the GENFI study.
Frontotemporal dementia (FTD) is a highly heritable condition with multiple genetic causes. In this study, similarities and differences of gray matter (GM) atrophy patterns were assessed among 3 common forms of genetic FTD (mutations in C9orf72, GRN, and MAPT). Participants from the Genetic FTD Initiative (GENFI) cohort with a suitable volumetric T1 magnetic resonance imaging scan were included (319): 144 nonmutation carriers, 128 presymptomatic mutation carriers, and 47 clinically affected mutation carriers. ⋯ Presymptomatic GM atrophy was observed particularly in the thalamus and cerebellum in the C9orf72 group, the anterior and medial temporal lobes in MAPT, and the posterior frontal and parietal lobes as well as striatum in GRN. Across all presymptomatic carriers, there were significant decreases in the anterior insula. These results suggest that although there are important differences in atrophy patterns for each group (which can be seen presymptomatically), there are also similarities (a fronto-insula-anterior cingulate network) that help explain the clinical commonalities of the disease.
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Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative motor neuron disease accompanied by both systemic and central nervous system-specific inflammation as well as deregulated energy metabolism. These potential pathogenetic factors have recently been found to mutually interact with the gut microbiota, raising the hypothesis of a link between microbiome alterations and ALS pathogenesis. The aim of our study was to assess whether ALS is associated with an altered composition of the fecal microbiota. ⋯ Comparing the 2 carefully matched groups, the diversity and the abundance of the bacterial taxa on the different taxonomic levels as well as PICRUSt-predicted metagenomes were almost indistinguishable. Significant differences between ALS patients and healthy controls were only observed with regard to the overall number of microbial species (operational taxonomic units) and in the abundance of uncultured Ruminococcaceae. Conclusively, ALS patients do not exhibit a substantial alteration of the gut microbiota composition.
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Neurobiology of aging · Nov 2017
Differential vulnerability of hippocampal subfields and anteroposterior hippocampal subregions in healthy cognitive aging.
In the present study, we investigated whether hippocampal subfields (cornu ammonis 1-3, dentate gyrus, and subiculum) and anteroposterior hippocampal subregions (head, body, and tail) follow the same trajectory with age using structural magnetic resonance imaging. We recruited 129 healthy volunteers, aged 18-85 years. Structural magnetic resonance imaging scans were acquired on a 4.7T system. ⋯ The total subiculum and the total dentate gyrus volumes were associated with age, while the total cornu ammonis 1-3 was not. Significant associations with age for the cornu ammonis 1-3 and the dentate gyrus volumes were present only in the hippocampal body, while the subiculum volumes were associated with age throughout the entire hippocampus. Subiculum volumes were more negatively related to age in men than in women.
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Neurobiology of aging · Sep 2017
ApoE influences regional white-matter axonal density loss in Alzheimer's disease.
Mechanisms underlying phenotypic heterogeneity in young onset Alzheimer disease (YOAD) are poorly understood. We used diffusion tensor imaging and neurite orientation dispersion and density imaging (NODDI) with tract-based spatial statistics to investigate apolipoprotein (APOE) ε4 modulation of white-matter damage in 37 patients with YOAD (22, 59% APOE ε4 positive) and 23 age-matched controls. Correlation between neurite density index (NDI) and neuropsychological performance was assessed in 4 white-matter regions of interest. ⋯ NODDI metrics indicate fractional anisotropy changes are underpinned by combinations of axonal loss and morphological change. Regional NDI in parieto-occipital white matter correlated with visual object and spatial perception battery performance (right and left, both p = 0.02), and performance (nonverbal) intelligence (WASI matrices, right, p = 0.04). NODDI provides tissue-specific microstructural metrics of white-matter tract damage in YOAD, including NDI which correlates with focal cognitive deficits, and APOEε4 status is associated with different patterns of white-matter neurodegeneration.