Charting cortical-layer specific area boundaries using Gibbs' ringing attenuated T1w/T2w-FLAIR myelin MRI

Area of Science:

• Neuroimaging
• Comparative Neuroanatomy
• Primate Brain Research

Background:

• Traditional cortical area definition relies on postmortem histology of cyto- and myelo-architecture.
• Recent MRI studies use T1w/T2w ratios to map cortical myelin in vivo, but Gibbs' ringing artifacts complicate layer analysis.

Purpose of the Study:

• To develop a novel, noninvasive MRI method for high-resolution mapping of cortical layer myeloarchitecture in living primates.
• To overcome Gibbs' ringing artifacts and enhance intra-cortical myelin contrast for precise areal delineation.

Main Methods:

• Utilized cortical layer thickness-adjusted T1w/T2w-FLAIR imaging to cancel Gibbs' ringing artifacts and enhance myelin contrast.
• Mapped whole-brain MRI measures onto twelve equivolumetric layers.
• Identified layer-specific myeloarchitectonic transitions using spatial gradients.

Main Results:

• Developed a novel imaging technique that effectively cancels Gibbs' ringing artifacts and enhances intra-cortical myelin contrast.
• Generated a putative 182 area/subarea partition of the macaque cerebral cortex based on laminar myelin gradients.
• Demonstrated high homology between macaque and human cortical myelin maps, suggesting conserved developmental programs.
• Validated the MRI method by showing it explains over 80% of the variance in laminar profiles compared to histological myelin stains.

Conclusions:

• The developed T1w/T2w-FLAIR method offers a noninvasive approach for precision mapping of layer myeloarchitecture in the primate cerebral cortex.
• The findings advance classical neuroanatomical work by providing in vivo insights into cortical organization.
• High cross-species homology in myelin maps supports a shared developmental trajectory of cortical myelin across primates.