Probabilities of white-matter connections were separately estimated
from each mask to all brain voxels with the FSL program
“probtrackX”. Per seed mask, 5000 paths were drawn from each
mask voxel, following the most likely white matter tract direction
given the principal fiber directions. This analysis yields a map in
which the value at each voxel reflects the statistical likelihood of a
connection between this voxel and the mask. The resulting probability
maps per seed-mask voxel were automatically combined in
FSL (Fig. 2C and D), divided by the number of paths drawn and by