Figure 8 .

LD-independent SNPs with p-values smaller than 5 x 10⁻⁶ show significant associations with FA in multiple fiber tracts. We used functional analysis of diffusion tensor tract statistics (FADTTS) (Zhu H et al. 2011) to test for associations between our top hits and FA within individual fiber tracts. Most variants have small global p-values across multiple tracts. Associations with the tract factor are often stronger than associations with individual tracts, revealing the power of this analysis approach. Some tracts, including the right and left optic tract (OTL and OTR), the left and right medial lemniscus (ML and MR), and the superior portions of the left and right cingulum (CLC and CRC) show relatively weak associations with these variants. Some variants appear to exert stronger effects in only a subset of tracts. In particular, rs2002371 shows stronger associations with various components of the arcuate fasciculus compared to other fiber tracts. An explanation of these abbreviations can be found in Supplementary Table 6.