  Probabilistic tractography based on diffusion weighted MRI has become a
powerful approach for quantifying structural brain connectivities. In several
works the similarity of probabilistic tractography and path integrals was
already pointed out. This work investigates this connection more closely. For
the so called Wiener process, a Gaussian random walker, the equivalence is
worked out. We identify the source of the asymmetry of usual random walkers
approaches and show that there is a proper symmetrization, which leads to a new
symmetric connectivity measure. To compute this measure we will use the
Fokker-Planck equation, which is an equivalent representation of a Wiener
process in terms of a partial differential equation. In experiments we show
that the proposed approach leads a symmetric and robust connectivity measure.
