Age-related estimates of aggregate g-ratio of white matter structures assessed using quantitative magnetic resonance neuroimaging.
Hum Brain Mapp
; 42(8): 2362-2373, 2021 06 01.
Article
em En
| MEDLINE
| ID: mdl-33595168
ABSTRACT
The g-ratio, defined as the inner-to-outer diameter of a myelinated axon, is associated with the speed of nerve impulse conduction, and represents an index of axonal myelination and integrity. It has been shown to be a sensitive and specific biomarker of neurodevelopment and neurodegeneration. However, there have been very few magnetic resonance imaging studies of the g-ratio in the context of normative aging; characterizing regional and time-dependent cerebral changes in g-ratio in cognitively normal subjects will be a crucial step in differentiating normal from abnormal microstructural alterations. In the current study, we investigated age-related differences in aggregate g-ratio, that is, g-ratio averaged over all fibers within regions of interest, in several white matter regions in a cohort of 52 cognitively unimpaired participants ranging in age from 21 to 84 years. We found a quadratic, U-shaped, relationship between aggregate g-ratio and age in most cerebral regions investigated, suggesting myelin maturation until middle age followed by a decrease at older ages. As expected, we observed that these age-related differences vary across different brain regions, with the frontal lobes and parietal lobes exhibiting slightly earlier ages of minimum aggregate g-ratio as compared to more posterior structures such as the occipital lobes and temporal lobes; this agrees with the retrogenesis paradigm. Our results provide evidence for a nonlinear association between age and aggregate g-ratio in a sample of adults from a highly controlled population. Finally, sex differences in aggregate g-ratio were observed in several cerebral regions, with women exhibiting overall lower values as compared to men; this likely reflects the greater myelin content in women's brain, in agreement with recent investigations.
Palavras-chave
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Axônios
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Envelhecimento
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Imageamento por Ressonância Magnética
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Neuroimagem
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Substância Branca
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Desenvolvimento Humano
Limite:
Adult
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Aged
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Aged80
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Female
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Humans
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Male
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Middle aged
Idioma:
En
Revista:
Hum Brain Mapp
Assunto da revista:
CEREBRO
Ano de publicação:
2021
Tipo de documento:
Article
País de afiliação:
Estados Unidos