Investigation and validation for cortical laminar structures of myelin and iron using χ-separation (chi-separation)

Motivation: Previous studies have demonstrated the correlations between iron and paramagnetic susceptibility and myelin and diamagnetic susceptibility. However, there has yet to be a quantitative layer-wise comparison with histology. Goal(s): Our objective is to validate laminar structures of χ-separation against histology in V1. Approach: In V1, we performed laminar profiling of χ-separation, iron-, and myelin histology. The profile was obtained by sampling points at 5% intervals along the cortical depth, oriented perpendicularly to the cortex. Results: The cortical depth profile reveals that both χpara with iron histology and χdia with myelin staining exhibit similar profiles and peaks at the location of the Gennari line. Impact: By comparing the cortical depth profile in the V1 region including the location of the Gennari line between χ-separation and histology, we have confirmed that χ-separation (χpara, χdia) accurately represents the quantitative amounts of iron and myelin with precision.