: 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.

Characterizing axonal myelination within the healthy population: a tract-by-tract mapping of effects of age and gender on the fiber g-ratio / Cercignani, Mara; Giulietti, Giovanni; Dowell, Nick G; Gabel, Matt; Broad, Rebecca; Leigh, P Nigel; Harrison, Neil A; Bozzali, Marco. - In: NEUROBIOLOGY OF AGING. - ISSN 1558-1497. - 49:(2017), pp. 109-118. [10.1016/j.neurobiolaging.2016.09.016]

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

Giulietti, Giovanni;
2017

Abstract

: 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.
2017
axonal conduction; lateralization; myelination; white matter
01 Pubblicazione su rivista::01a Articolo in rivista
Characterizing axonal myelination within the healthy population: a tract-by-tract mapping of effects of age and gender on the fiber g-ratio / Cercignani, Mara; Giulietti, Giovanni; Dowell, Nick G; Gabel, Matt; Broad, Rebecca; Leigh, P Nigel; Harrison, Neil A; Bozzali, Marco. - In: NEUROBIOLOGY OF AGING. - ISSN 1558-1497. - 49:(2017), pp. 109-118. [10.1016/j.neurobiolaging.2016.09.016]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11573/1670334
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