Figure 2. FA and MD maps are affected by site.
(a) Density of the FA values for WM voxels for each participant, colored by site. (b) MA-plot for site differences in FA. The y-axis represents the differences in FA between Site 1 and Site 2, while the x-axis shows the average FA across sites. FA maps that would be free of site effects would result in an MA-plot centered around 0. The upper-left part of the scatterplot shows that several voxels appear to be differently affected by site in comparison to the rest of the voxels. (c) Boxplot of FA values for voxels located in two regions of interest (Cuneus left and Putamen left), depicted per site (FA values were averaged by site at each voxel separately). This shows that the magnitude of the difference in means between the two sites is region-specific. (d–f) Same as (a–c), but for the MD maps.