FIG. 4.

Tracking of the CST (yellow) reveals greater visualization with successively more advanced tractography methods: with a DTI model (A); with a free-water corrected DTI model, showing a mild increase (B); with a HARDI model and probabilistic tracking (C); and in a multicompartment model with free-water correction and probabilistic tracking (D). The ability to accurately resolve white matter fibers that cross within a voxel has been a limiting factor; the absence of DTI tracts on a postprocessed scan does not preclude the underlying presence of white matter tracts. A variety of solutions like probabilistic tracking and HARDI have been developed to mitigate this limitation. Analysis of stereotactic cortical and subcortical stimulation points (E; e.g., red and green cortical points) in conjunction with tractography represents an important methodology in validation studies.