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Introducing axonal myelination in connectomics - A preliminary analysis of g-ratio distribution in healthy subjects.pdf (1.52 MB)

Introducing axonal myelination in connectomics: a preliminary analysis of g-ratio distribution in healthy subjects

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posted on 2023-06-09, 07:58 authored by Matteo Mancini, Giovanni Giulietti, Nicholas DowellNicholas Dowell, Barbara Spanò, Neil Harrison, Marco Bozzali, Mara Cercignani
Microstructural imaging and connectomics are two research areas that hold great potential for investigating brain structure and function. Combining these two approaches can lead to a better and more complete characterization of the brain as a network. The aim of this work is characterizing the connectome from a novel perspective using the myelination measure given by the g-ratio. The g-ratio is the ratio of the inner to the outer diameters of a myelinated axon, whose aggregated value can now be estimated in vivo using MRI. In two different datasets of healthy subjects, we reconstructed the structural connectome and then used the g-ratio estimated from diffusion and magnetization transfer data to characterise the network structure. Significant characteristics of g-ratio weighted graphs emerged. First, the g-ratio distribution across the edges of the graph did not show the power-law distribution observed using the number of streamlines as a weight. Second, connections involving regions related to motor and sensory functions were the highest in myelin content. We also observed significant differences in terms of the hub structure and the rich-club organization suggesting that connections involving hub regions present higher myelination than peripheral connections. Taken together, these findings offer a characterization of g-ratio distribution across the connectome in healthy subjects and lay the foundations for further investigating plasticity and pathology using a similar approach.


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