Figure 1.

Flowchart illustrating the processing workflow. (A) The PaCER toolbox (in revision) was used to accurately reconstruct DBS electrodes using postoperative CT data. (B) An automated pipeline within PaCER (in review) was used to rigidly coregister intrasubject scans (FSL‐Flirt) and nonlinearly transform basal ganglia structures from atlas‐ to patient‐space (ANTs). (C) The T2w scan was upsampled to a 0.5 mm isotropic resolution and used to manually segment the STN (ITKsnap). (D) First, the T1w scans were used to parcellate the frontal lobe into one motor cortex (MC; supplementary, pre‐ and primary motor cortex) and one prefrontal (PF) region (Freesurfer). Next, the DWI data were preprocessed (de‐noising, gibbs‐correction, combined motion‐ and eddy‐current correction and intensity inhomogeneity correction) and a higher order diffusion model was fitted using constrained spherical deconvolution (MRtrix3). Finally, tractography was performed using a probabilistic algorithm (iFOD2); streamlines were seeded from the STN segmentation (500 seeds/voxel), those connecting directly with the ipsilateral MC and PF were extracted and resampled to track density maps allowing calculation of the ratio between MC and PF connections across STN voxels. The maps were thresholded in a winner‐takes‐all approach to define a STN‐subregion consisting of voxels dominated by MC connectivity (50% streamlines connecting with MC).