Figure 3.

Illustration of proximal tissue density (PTD) for depth electrode contacts. A) A schematic drawing of PTD algorithm for depth contacts. The augmented contact (light blue lines, red dot represents the contact centroid) is surrounded by both gray matter (gray voxels) and white matter (white voxels). Each voxel is 1×1×1 mm³. The number of gray and white matter voxels are used for PTD calculation. B) PTD distribution across 23 human subjects (3158 depth contacts). Bins of PTD value are shown in x-axis. The percentage value is calculated by dividing the number of contacts found within each bin by the total number of depth contacts across all subjects. PTD value of depth contacts that are not located in gray matter or white matter (e.g., deep subcortical structures) are not displayed.