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Characterizing axonal myelination within the healthy population: a tract-by-tract mapping of effects of age and gender on the fiber g-ratio

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posted on 2023-06-09, 04:28 authored by Mara Cercignani, Giovanni Guilietti, Nicholas DowellNicholas Dowell, Matthew Gabel, Rebecca Broad, Nigel LeighNigel Leigh, Neil Harrison, Marco Bozzali
The g-ratio, equal to the ratio of the inner-to-outer diameter of a myelinated axon, is associated with the speed of conduction, and thus reflects axonal function and integrity. It is now possible to estimate an “aggregate” g-ratio in vivo using MRI. The aim of this study was to assess the variation of the MRI-derived fiber g-ratio in the brain of healthy individuals, and to characterize its variation across the lifespan. Thirty-eight healthy participants, aged between 20 and 76, were recruited. Whole-brain g-ratio maps were computed and analyzed voxel-wise. Median tract g-ratio values were also extracted. No significant effect of gender was found, whereas age was found to be significantly associated with the g-ratio within the white matter. The tract-specific analysis showed this relationship to follow a nearly-linear increase, although the slope appears to slow down slightly after the 6th decade of life. The most likely interpretation is a subtle but consistent reduction in myelin throughout adulthood, with the density of axons beginning to decrease between the 4th and 5th decade.

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Publication status

  • Published

File Version

  • Published version

Journal

Neurobiology of Aging

ISSN

0197-4580

Publisher

Elsevier

Volume

49

Page range

109-118

Department affiliated with

  • BSMS Neuroscience Publications

Full text available

  • Yes

Peer reviewed?

  • Yes

Legacy Posted Date

2016-12-19

First Open Access (FOA) Date

2016-12-19

First Compliant Deposit (FCD) Date

2016-12-19

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