ZDHHC9 structural connectome - Supplementary Materials

Illustration of tractography results

The structural connectome was based on streamline tractography. A connections between regions was indicated if at least X number of fibres intersected with both ROIs. The resulting connectome description depends on the ability of the tractography algorithm to provide a biologically meaningful account of macroscopic white matter connection. The results presented in the main manuscript are based on a constrained spherical deconvolution model with probabilistic tractography. This approach is able to resolve crossing fibres (Tournier 2008) and shows high overlap in comparison with post-mortem tract tracing (Calamante 2012). The following figure shows a representative example of the whole brain connectome constructed through this approach. Please note that the density is considerably reduced in this depiction; only every 20th streamline is shown.

\label{figure:tractography_illustration}Representative results of whole-brain streamline tractography for one participant in the ZDHHC9 group (top) and the control group (bottom). Both are shown at 5% density for illustrative purposes. The left side shows a saggital view of the left hemisphere and the right side a dorsal axial view. The streamlines are colour-coded according to diffusion imaging conventions, i.e. blue:inferior-superior, red:left-right, green:anterior-posterior.

Group-average connection matrices

Visualization of connectome results is associated with various limitations. There is a general trade-off between providing anatomical context and presenting a complete account of connections (Margulies 2013). The images presented in the main manuscript provide the anatomical context, but had to be thresholded at a high cut-off. Otherwise, numerous connections with low edge weight would have obscured the image. Here, unthresholded connection matrices are presented that show all connections, but do not provide anatomical context.