Inclusion Criteria:  Age between 18 and 85 years of age. Preparing to undergo a functional neurosurgical intervention (e.g., DBS, RFA, GKR or MRgFUS) at TWH (not applicable for healthy volunteers). Participants must be able to understand the purpose of this research and must sign the informed consent form. Participants must understand that the role of this research is to enhance our understanding of brain functioning and that he/she will not directly or indirectly benefit from the study.  Exclusion Criteria:  Contraindication for an MRI (e.g., implanted cardiac device, metal in eyes, aneurysm clip, etc.). Participants who have serious cognitive or psychological impairments and cannot give informed consent. Participants who are unable to communicate effectively or efficiently (e.g., patients suffering from speech deficits (dysarthria, aphasia) or are non-English speaking).