Two axes of white matter development.

Area of Science:

• Neuroscience
• Developmental Neuroscience
• Neuroimaging

Background:

• Understanding white matter maturation is crucial for cognitive development.
• Previous research often assumed uniform development along white matter tracts.
• Human white matter development along major tracts remains largely uncharacterized.

Purpose of the Study:

• To identify fundamental patterns of white matter maturation along major tracts in humans.
• To investigate developmental variation across the length of cortico-cortical tracts.
• To challenge the assumption of uniform white matter tract development.

Main Methods:

• Utilized diffusion MRI data from three large-scale, cross-sectional datasets (N=2716).
• Examined developmental variation in youth aged 5-23 years.
• Analyzed major, long-range cortico-cortical tracts.

Main Results:

• Identified two replicable axes of white matter development: a deep-to-superficial axis and a sensorimotor-to-association hierarchical axis.
• Superficial tract regions near the cortex showed greater age-related changes than deep regions.
• Superficial tract development aligned with cortical hierarchy, with sensorimotor-adjacent regions maturing earlier than association-adjacent regions.

Conclusions:

• White matter tracts do not mature uniformly along their length.
• Developmental variation along tracts has potential functional implications, such as mitigating ephaptic coupling and tuning neural synchrony.
• Findings refine our understanding of neural transmission refinement during youth.