Figure 2: Substantia nigra ROIs. Overall means across different groups: fractional anisotropy (blue) and mean diffusivity (green). Error bars denote ± 1 standard error of the mean (SEM). One-way ANOVA analyses with age and sex as covariates were performed among each group. Mean values for each group are CON (FA mean= 0.59, MD mean=0.62), AD (FA mean= 0.51 MD mean= 0.75), PD (FA mean= 0.52 MD mean= 0.67), and PDD (FA mean=0.44 MD mean=0.86). Stars denote significant values for FA CON>PDD (at p=0.004*), and MD at PDD>CON (at p=0.01**).