RADIAL AND TANGENTIAL FIBER COMPONENTS IN HUMAN SUPERFICIAL WHITE MATTER AND THEIR ASSOCIATIONS WITH MACROSCALE FUNCTION

The superficial white matter (SWM) beneath the human cortex comprises a complex network of short- and long-range fiber systems that facilitate communication between cortical regions. Within this layer, two primary fiber components have been identified: subcortical U-shaped fibers (U-fibers) and long-range fibers. U-fibers predominantly follow a tangential path along the gray matter-white matter border, while long-range fibers extend radially into the deeper white matter to link distant cortical areas.

To better understand these fiber populations' structural and functional roles, researchers have created a surface-based method to differentiate between their radial and tangential components. This approach involves measuring apparent fiber density (AFD), fractional anisotropy (FA), and mean diffusivity (MD) to quantify fiber properties.

Additionally, the study examines depth-dependent microstructural patterns and their correlation with established cortical organization and hierarchical specializations. The framework's validity is confirmed through comparison with post-mortem white matter dissections and tractography-based bundle analyses. By relating the predominance of radial or tangential fibers to spatial functional variability patterns, the research uncovers unique structural and functional characteristics associated with each fiber component.

These discoveries offer a foundation for exploring the roles of radial and tangential SWM fibers in cortical organization and specialized function.