I have a question on interpretation of probabilistic tractography using the 2 fiber model. In Behrens et al 2003 pp 1085 it is stated: "It is tempting to think of this distribution as a distribution of connections from the seed point. This is manifestly not the case. According to the model used earlier in this section, this spatial pdf represents confidence bounds on the location of the most probable single connection." and this makes perfect sense given the modelling of a single fiber per voxel. My question is how does this interpretation change in the 2 fiber model case? How does one know whether the spread is due to a 2nd fiber being allowed vs. confidence on a single fiber?