Figure 4. Spatial distribution of age associations and glial cell enrichment across whole brain white matter indexed by fractional anisotropy (FA).

(A) Spatial distribution of age associations across whole brain white matter tracts as measured by fractional anisotropy (FA) depict a significant negative age association with FA (blue indicates negative association, red indicates positive association). (B) Age-regressed FA estimates (b) show significant differences between white matter tract classes (p<0.05). Association tracts generally show the greatest negative age-regressed FA, significantly greater than projection (t=−2.72, p=0.010) and complex cerebellar tracts (t=−2.21, p=0.038). All reported p-values are FDR-corrected. (C) Spatial distribution of glial cell enrichment (i.e., astrocytes, microglia, oligodendrocytes, OPC) on whole brain white matter FA tract measures estimated using LDSC partitioned heritability (Dark blue indicates low enrichment, bright yellow indicates high enrichment). Analyses of other diffusivity modalities are available in the supplement.