Figure 5. Cell type distributions track with age-related associations across diffusion measures.

Cell type enrichment estimates were calculated based on compiling differentially expressed marker genes across cell subtypes identified by Lake et al (78), using LDSC (linkage disequilibrium score regression) partitioned heritability. Twenty cell types were rank ordered by spatial correlation to whole brain white matter tracts across diffusivity measures. (A) Table cells reflect correlations between age-regressed estimates and cell type enrichment, calculated by Spearman’s Rho. Warm red colors indicate positive correlation, cool blue colors indicate negative correlation, and significant correlations that survived FDR correction (p<0.05) are highlighted by bolded cells. (B) Scatter plots colored by the 20 respective diffusivity measure depict the positive/negative relationship between age-regressed diffusion estimates and oligodendrocyte enrichment (FA=fractional anisotropy, MD=mean diffusivity, L1, L2, L3 representing individual eigenvalues λ1, λ2, λ3 relative to the diffusion tensor). Oligodendrocyte enrichment was significantly negatively correlated with FA, and inversely correlated for the other diffusivity metrics, such as MD and L1–3.