Inclusion Criteria:  Either already implanted with DBS electrodes or undergoing DBS implantation in one of the defined nuclei of interest (for Surrey or Rochester: STN, PPN, Hypothalamus, PAG/PVG - for the Mayo clinic, may use hippocampus or ANT) for standard clinical care during the period of the study Male or female, aged 18 to 85 Be willing and able to give written and oral informed consent Ability to complete all required study procedures including travelling to the Sleep Centre and staying overnight By the time of the first visit to Surrey, participants should have already had their stimulation settings programmed by the Functional Neurosurgery team and have been stable on the settings for at least two weeks, as per their routine clinical care. For patients with chronic pain, they should be stable on their current medication and settings  Exclusion Criteria:  Cognitive impairment (judged by the clinician taking consent as not having sufficient mental capacity to understand the study and its requirements). This is including anyone who, in the opinion of the clinician taking consent is unlikely to retain sufficient mental capacity for the duration of their involvement in the study. Patients with any other medical condition that would interfere with study conduct or make it unsafe for them to participate. Such conditions may be poorly controlled diabetes, poorly controlled/end stage heart disease, renal failure as well as recurrent, uncontrolled seizures or epilepsy. Participants who have started new medication or changed doses 3 weeks prior to a study visit may not be eligible as deemed by the PI of the study. Patients on medication that can affect the study results (such as hypnotics - benzodiazepines and analogues), at the discretion of the PI. Patients currently taking ketamine Alcohol intake exceeding 28 units per week.