Deep Brain Stimulation (DBS) is commonly used for a range of neurological disorders, but its mechanisms of action are still unclear. This can be overcome by using diffusion tensor imaging. Anatomic connections between different parts of the brain may be analyzed. In our lab, studies are in progress to explore connectivity profiles and improve DBS efficiency.
In a recent paper published with LMU in NeuroImage, we found that stimulation of ventral and dorsal GPi, for Dystonia patients, belong to different functional and anatomic motor subsystems, which may justify the opposite motor effects.
Hemiballism may arise as a rare consequence of focal basal ganglia lesions. Pathophysiologically, there is a controversy between the role of the STN as the exclusive lesion localization as opposed to several brain regions in which lesions may induce hemiballism. This is most likely due to a motor circuit affection.
We analysed focal vascular lesions inducing hemiballism (n=8), their localization and connectivity profile. We provide evidence for the involvement of the subthalamo-pallido-thalamic pathways in the pathogenesis of hemiballism, which is consistent with data on experimental hemiballism in animals. 
-  Rozanski, V. E., Vollmar, C., Cunha, J. P., Tafula, S. M. N., Ahmadi, S. A., Patzig, M., … & Bötzel, K. (2014). Connectivity patterns of pallidal DBS electrodes in focal dystonia: a diffusion tensor tractography study. Neuroimage, 84, 435-442.
-  Rozanski, V. E., Wick, F., Moreira da Silva, N., Ahmadi, S. A., Kammermeier, S., Cunha, J. P. S., … & Vollmar, C. (2016). A connectivity-based approach to the pathophysiology of hemiballism. Basal Ganglia, 6(2), 107-113.
-  Rozanski, V. E., Moreira da Silva, N., Ahmadi, S. A., Mehrkens, J., da Silva Cunha, J., Houde, J. C., … & Descoteaux, M. (2016). The role of the pallidothalamic fibre tracts in deep brain stimulation for dystonia: A diffusion MRI tractography study. Human Brain Mapping.