Fig. 6.

The figure shows data (red) and Gaussian process ($\mathcal{G}\mathcal{P}$) fit (grey) from a b = 7000 shell from the pilot phase of the HCP. The six panels correspond to six randomly selected voxels in a transversal slice at the level of the Centrum Semiovale. The hyperparameters for the $\mathcal{G}\mathcal{P}$ was the same for all voxels (and calculated from a random selection of 1000 intracerebral voxels). It can be seen that the $\mathcal{G}\mathcal{P}$ has been able to successfully model the signal from the six voxels despite exhibiting vastly different signal profiles. It can for example be appreciated from the signal that the top panel in the middle column corresponds to a three-way crossing fibre, the top panel in the right column a two-way crossing fibre and the lower panel in the middle column a single (dominating) fibre. The top-left and bottom-right panels correspond to grey matter voxels.