Anatomical variability captured by the priors in an example training set of 30 healthy subjects. The plots show the fraction of training samples corresponding to the most commonly encountered label, averaged over all segments along the length of each pathway. This was computed for the labels that intersect the pathway (f0) and for the nearest neighboring labels in the left, right, anterior, posterior, superior, and inferior directions (fL, fR, fA, fP, fS, and fI, respectively). The higher the fraction, the lower the variability of the labels across training samples.