Studying Movement Control in Parkinson's Disease Using Closed Loop Deep Brain Stimulation

Study Summary Patients will undergo standard 2 part deep brain stimulation implantation (electrode implantation day 1, battery and stimulator implantation approximately day 7, home approximately day 10). The experiments will be performed whilst the patients are inpatients between the two operations and will therefore not require any extra visits or delay in starting therapeutic deep brain stimulation. This paradigm is the standard method for conducting local field potential research in human and represents the paradigm by which the vast majority of previous research in this area has been conducted. Patients will be tested either at Oxford University Hospitals National Health Service Trust or University College London National Health Service Trust.

At least 24h after electrode implantation (first of the two surgeries) patients will be approached about the study and left with the patient information sheet for 24 hours, before further discussion, and, if appropriate consent.

Thereafter, the following procedures will be undertaken:

1. The subjects will participate in a short assessment testing their cognitive function and fill out questionnaires regarding handedness and impulsiveness traits . Furthermore, they will be introduced to the three motor tasks, which they will perform during the definitive test. Together, these assessments will take approximately one hour.

Prior to the next steps, which will be conducted on the same day or 1-3 days later(depending on the preferences of the participant), participants will be requested to withhold their usual medication overnight so that they are assessed off medication on the morning of the tests. 2. Deep brain stimulation will be evaluated in order to find the best stimulation parameters ( the settings, which yield the best clinical benefit) for each individual patient. This will take approximately 1 hour and is part of the standard clinical procedure. 3. Recordings will be made from the deep brain stimulation electrodes and electrodes placed on the surface of the head in order to assess activity and communication within the brain. During the recordings participants will perform three motor tasks using their hands. In the first two tasks they have to decide whether to press a button on a computer mouse or refrain from a response depending on the nature of some small dots moving in different directions on a computer screen. This will allow assessing patients' ability to perform and inhibit movements. In the third task they are asked to press a button depending on the direction of an arrow presented in the middle of the screen, while ignoring arrows around this central cue. This additional task will allow assessing patients' ability to control conflicting response tendencies. The recordings will be conducted three times: During closed loop deep brain stimulation, open loop deep brain stimulation and while the stimulator is turned off. The order of these sessions will be randomized and counter-balanced across participants. The experimental recordings will take approximately 2 hours.