DBS DBS programming algorithm DBS side effects Medicine Parkinson's disease axial symptoms chronic pain clonidine closed loop cognitive behavioral therapy coping strategies deep brain stimulation depression dexmedetomidine electrophysiology general anesthesia genetics illness perceptions illness representations imaging inferior thalamic peduncle intraoperative computed tomography intraoperative magnetic resonance imaging lead externalization levodopa local anesthesia magnetic resonance imaging major depressive disorder medial forebrain bundle medial prefrontal cortex