Regional White Matter Scaling in the Human Brain

Area of Science:

• Neuroscience
• Human Anatomy
• Brain Imaging

Background:

• Primate cortical organization scales with brain size, featuring disproportionate expansion of associative cortices and relative contraction of sensorimotor systems.
• Previous research has not established equivalent scaling maps for regional white matter anatomy in humans.

Purpose of the Study:

• To investigate how regional white matter volume (WMV) scales with interindividual variation in total brain volume in humans.
• To examine the relationship between gray matter and white matter scaling patterns.
• To compare the scaling of WMV with white matter microstructure measures.

Main Methods:

• Analysis of three large-scale neuroimaging datasets comprising 2391 typically developing humans.
• Examination of regional white matter volume (WMV) scaling across individuals with varying brain volumes.
• Measurement of white matter microstructure using fractional anisotropy (FA) and magnetization transfer (MT).

Main Results:

• WMV scaling is regionally heterogeneous: larger brains exhibit relatively greater WMV in anterior/posterior cortical regions and the corpus callosum, but less in subcortical areas.
• Positive WMV scaling regions connect areas of positive gray matter scaling in the cortex, indicating coordinated anatomical organization.
• White matter microstructure measures (FA and MT) scale negatively with brain size and show distinct spatial patterns compared to WMV scaling.

Conclusions:

• Regional white matter anatomy systematically scales with human brain size, mirroring patterns observed in gray matter.
• The findings reveal a coordinated coupling between gray and white matter organization during brain size variation.
• Distinct scaling patterns for WMV and white matter microstructure provide a more comprehensive understanding of human brain anatomic scaling.