Fig. 4: Manhattan plot and spatial mapping of the association between the dMRI tensor mode measure and SNP rs4935898 (ROBO3).

a, The Manhattan plot relates to the original GWAS for the IDP of tensor mode in the crossing pontine tract associated with rs4935898. b–d, Tensor mode was averaged across all 6,807 subjects with approximately zero copies of the non-reference allele, and the average from all 703 subjects that had approximately one copy was subtracted from that, for display in red/yellow–blue/light blue here, thresholded at 0.05 (b, d). b, Results are shown overlaid on the MNI152 T1 structural image; by contrast, background in c and d is the UK Biobank average fractional anisotropy image, which shows clear tract structure within the brainstem. c, Orientation of the fibre tracts (in red, running left to right). The spatial distribution (not shown) for the effects of rs2286184 (SEMA3D) on tensor mode is almost identical to that of rs4935898, being again extremely spatially specific, with no extended effect elsewhere in the brain. These voxelwise SNP association maps were calculated from the discovery sample of 8,428 subjects (see main text).