Quantitative Measurement of Macromolecular Tissue Properties in White and Gray Matter in Healthy Aging and Amnestic MCI

We investigate the relationship between Gray matter’s volume vis-a-vis White matter’s integrity indices, such Axial diffusivity, Radial diffusivity, Mean diffusivity, and Fractional anisotropy, in individuals undergoing healthy aging. We investigated MRI scans of 177 adults across 20 to 85 years. We used Voxel-based morphometry, and FDT-FSL analysis for estimation of Gray matter volume and White matter’s diffusion indices respectively. Across the life span, we observed an inter-relationship between the Gray matter and White matter, namely that both Axial diffusivity and Mean Diffusivity show strong correlation with Gray matter volume, along the aging process. Furthermore, across all ages the Fractional anisotropy and Mean diffusivity are found to be significantly reduced in females when compared to males, but there are no significant gender differences in Axial Diffusivity and Radial diffusivity. We conclude that for both genders across all ages, the Gray matter’s Volume is strongly correlated with White matter’s Axial Diffusivity and Mean Diffusivity, while being weakly correlated with Fractional Anisotropy. Our study clarifies the multi-scale relationship in brain tissue, by elucidating how the White matter’s micro-structural parameters influences the Gray matter’s macro-structural characteristics, during healthy aging across the life-span.

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Age-related networks of regional covariance in MRI gray matter: Reproducible multivariate patterns in healthy aging

NeuroImage ◽

10.1016/j.neuroimage.2009.09.051 ◽

2010 ◽

Vol 49 (2) ◽

pp. 1750-1759 ◽

Cited By ~ 69

Author(s):

Kaitlin L. Bergfield ◽

Krista D. Hanson ◽

Kewei Chen ◽

Stefan J. Teipel ◽

Harald Hampel ◽

...

Keyword(s):

Gray Matter ◽

Healthy Aging ◽

Age Related

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The prevalence of cortical gray matter atrophy may be overestimated in the healthy aging brain.

Neuropsychology ◽

10.1037/a0016161 ◽

2009 ◽

Vol 23 (5) ◽

pp. 541-550 ◽

Cited By ~ 31

Author(s):

Saartje Burgmans ◽

Martin P. J. van Boxtel ◽

Eric F. P. M. Vuurman ◽

Floortje Smeets ◽

Ed H. B. M. Gronenschild ◽

...

Keyword(s):

Gray Matter ◽

Healthy Aging ◽

Aging Brain ◽

Gray Matter Atrophy ◽

Cortical Gray Matter

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The causal structure of age-dependent limbic decline: fornix white matter glia damage causes hippocampal grey matter damage, not vice versa

10.1101/440917 ◽

2018 ◽

Author(s):

Claudia Metzler-Baddeley ◽

Jilu P. Mole ◽

Rebecca Sims ◽

Fabrizio Fasano ◽

John Evans ◽

...

Keyword(s):

White Matter ◽

Gray Matter ◽

Mediation Analysis ◽

Late Onset ◽

Causal Structure ◽

Tissue Loss ◽

Hippocampal Damage ◽

White Matter Damage ◽

Tissue Properties ◽

Age Related

AbstractAging leads to gray and white matter decline but their causation remains unclear. We explored two broad classes of models of age and dementia risk related brain changes. The first class of models emphasises the importance of gray matter: age and risk-related processes cause neurodegeneration and this causes damage in associated white matter tracts. The second class of models reverses the direction of causation: aging and risk factors cause white matter damage and this leads to gray matter damage. We compared these models with linear mediation analysis and quantitative multi-modal MRI indices (from diffusion, quantitative magnetization transfer and relaxometry imaging) of tissue properties in two limbic structures implicated in age-related memory decline: the hippocampus and the fornix in 166 asymptomatic individuals (aged 38 - 71 years). Aging was associated with apparent glia but not axon density damage in the fornix. Mediation analysis unambiguously supported white matter damage causing gray matter decline; controlling for fornix glia damage, the correlation between age and hippocampal damage disappears, but not vice versa. Fornix and hippocampal tissue loss were both associated with reductions in episodic memory performance. The implications of these findings for neuroglia and neurodegenerative models of aging and late onset dementia are discussed.

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Diffusion MRI Anisotropy in the Cerebral Cortex is Determined by Unmyelinated Tissue Features

10.1101/2021.09.02.458694 ◽

2021 ◽

Author(s):

Colin Reveley ◽

Frank Q Ye ◽

Rogier B Mars ◽

David A Leopold

Keyword(s):

Cerebral Cortex ◽

Gray Matter ◽

Ex Vivo ◽

High Signal ◽

Water Molecules ◽

Nissl Staining ◽

Tissue Properties ◽

Marmoset Monkey ◽

Cellular Substructure ◽

The Brain

The diffusion of water molecules through the brain is constrained by tissue and cellular substructure, which imposes an anisotropy that can be measured through diffusion magnetic resonance imaging (dMRI). In the white matter, myelinated axons strongly shape diffusion anisotropy; however, in gray matter the determinants of dMRI signals remain poorly understood. Here we investigated the histological tissue properties underlying dMRI anisotropy and diffusivity in the cerebral cortex of the marmoset monkey. We acquired whole brain ex vivo dMRI data designed for high signal-to-noise at ultra-high (150μm) resolution. We compared the MRI to myelin- and Nissl-stained histological sections obtained from the scanned brain. We found that dMRI anisotropy corresponds most strongly not with cortical myelin content, but rather with the microscale anisotropy of tissue features, most notably those unmyelinated features highlighted by Nissl staining. The results suggest that dMRI anisotropy in gray matter derives from the organization of unmyelinated neurites, which are known to be affected by neurodegenerative diseases.

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Increased functional connectivity supports language performance in healthy aging despite gray matter loss

Neurobiology of Aging ◽

10.1016/j.neurobiolaging.2020.09.015 ◽

2021 ◽

Vol 98 ◽

pp. 52-62 ◽

Cited By ~ 1

Author(s):

Aurélie Pistono ◽

Laura Guerrier ◽

Patrice Péran ◽

Marie Rafiq ◽

Mélanie Giméno ◽

...

Keyword(s):

Functional Connectivity ◽

Gray Matter ◽

Healthy Aging ◽

Language Performance ◽

Gray Matter Loss

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Reply to Fjell et al. (2010) and Raz and Lindenberger (2010): The prevalence of cortical gray matter atrophy may be overestimated in the healthy aging brain.

Neuropsychology ◽

10.1037/a0018826 ◽

2010 ◽

Vol 24 (2) ◽

pp. 264-266

Author(s):

Saartje Burgmans ◽

Martin P. J. van Boxtel ◽

Eric F. P. M. Vuurman ◽

Floortje Smeets ◽

Ed H. B. M. Gronenschild ◽

...

Keyword(s):

Gray Matter ◽

Healthy Aging ◽

Aging Brain ◽

Gray Matter Atrophy ◽

Cortical Gray Matter

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Multiple b-values improve discrimination of cortical gray matter regions using diffusion MRI: an experimental validation with a data-driven approach

Magnetic Resonance Materials in Physics Biology and Medicine ◽

10.1007/s10334-021-00914-3 ◽

2021 ◽

Author(s):

Tara Ganepola ◽

Yoojin Lee ◽

Daniel C. Alexander ◽

Martin I. Sereno ◽

Zoltan Nagy

Keyword(s):

Gray Matter ◽

Diffusion Mri ◽

Repeated Measurements ◽

Data Driven ◽

Correct Classification ◽

Classification Rate ◽

Tissue Properties ◽

Cortical Areas ◽

Human Connectome Project ◽

Data Driven Approach

Abstract Objective To investigate whether varied or repeated b-values provide better diffusion MRI data for discriminating cortical areas with a data-driven approach. Methods Data were acquired from three volunteers at 1.5T with b-values of 800, 1400, 2000 s/mm2 along 64 diffusion-encoding directions. The diffusion signal was sampled from gray matter in seven regions of interest (ROIs). Rotational invariants of the local diffusion profile were extracted as features that characterize local tissue properties. Random forest classification experiments assessed whether classification accuracy improved when data with multiple b-values were used over repeated acquisition of the same (1400 s/mm2) b-value to compare all possible pairs of the seven ROIs. Three data sets from the Human Connectome Project were subjected to similar processing and analysis pipelines in eight ROIs. Results Three different b-values showed an average improvement in correct classification rates of 5.6% and 4.6%, respectively, in the local and HCP data over repeated measurements of the same b-value. The improvement in correct classification rate reached as high as 16% for individual binary classification experiments between two ROIs. Often using only two of the available three b-values were adequate to make such an improvement in classification rates. Conclusion Acquisitions with varying b-values are more suitable for discriminating cortical areas.

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