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Superficial white matter fiber systems impede detection of long-range cortical connections in diffusion MR tractography

journal contribution
posted on 2023-06-08, 22:03 authored by Colin Reveley, Anil SethAnil Seth, Carlo Pierpaoli, Afonso C Silva, David Yu, Richard C Saunders, David Leopold, Frank Q Ye
In vivo tractography based on diffusion magnetic resonance imaging (dMRI) has opened new doors to study structure–function relationships in the human brain. Initially developed to map the trajectory of major white matter tracts, dMRI is used increasingly to infer long-range anatomical connections of the cortex. Because axonal projections originate and terminate in the gray matter but travel mainly through the deep white matter, the success of tractography hinges on the capacity to follow fibers across this transition. Here we demonstrate that the complex arrangement of white matter fibers residing just under the cortical sheet poses severe challenges for long-range tractography over roughly half of the brain. We investigate this issue by comparing dMRI from very-high-resolution ex vivo macaque brain specimens with histological analysis of the same tissue. Using probabilistic tracking from pure gray and white matter seeds, we found that 50% of the cortical surface was effectively inaccessible for long-range diffusion tracking because of dense white matter zones just beneath the infragranular layers of the cortex. Analysis of the corresponding myelin-stained sections revealed that these zones colocalized with dense and uniform sheets of axons running mostly parallel to the cortical surface, most often in sulcal regions but also in many gyral crowns. Tracer injection into the sulcal cortex demonstrated that at least some axonal fibers pass directly through these fiber systems. Current and future high-resolution dMRI studies of the human brain will need to develop methods to overcome the challenges posed by superficial white matter systems to determine long-range anatomical connections accurately.

History

Publication status

  • Published

File Version

  • Published version

Journal

Proceedings of the National Academy of Sciences of the United States of America PNAS

ISSN

1091-6490

Publisher

National Academy of Sciences

Issue

21

Volume

112

Article number

E2820-E2828

Department affiliated with

  • Informatics Publications

Full text available

  • No

Peer reviewed?

  • Yes

Legacy Posted Date

2015-08-06

First Compliant Deposit (FCD) Date

2021-03-08

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