Individual localization of thalamic contacts
Thalamic contacts were localized by using the procedure described below (see also Simor et al. 2021). In order to individually localize the thalamic contacts preoperative MRI and postoperative CT images were co-registered using tools available in the FMRIB Software Library (FSL, Oxford, FLIRT, linear registration, 6 degrees of freedom). Threshold was applied on the co-registered CT scans to achieve the desired level of density for proper identification of the lead, thus removing the surrounding brain tissue. Coordinates of the most distal point of the lead were identified and a more proximal point was selected along the line of the contacts to mathematically reconstruct the coordinates of the center point of each contact using Euclidean distance in three dimensional space. These points superimposed over the T1 MRI image provided a guideline for contact localization by examining their location to the anatomical boundaries of the ANT. Anatomical positions according to standard coordinates of the contacts were double-checked by using the mamillothalamic tract as an anatomical guide to localize the ANT. In case of convergent results of these two methods, the ANT (for 15 patients) and MD (for 10 patients) contacts were considered as subjects for further digital signal processing in the present study.