A note on interpretation

The implication of accounting for the uncertainty in local fiber directions, and hence estimating a spatial probability distribution of connectivity from the seed point, is that the recovered connectivity distribution is spread in space (see Global Connectivity Estimation: Results). 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. It is certainly true that some of the uncertainty estimated locally is likely to be due to partial volume effects, such as a spread of fiber directions in the voxel, and therefore the presence in the brain of multiple connection sites from the seed may result in a diffuse spatial pdf. However, while the model of diffusion at each voxel includes only a single fiber direction, the global inference is clearly on a single pathway.