Characterizing the Pathophysiological Role of the Pallido-thalamocortical Motor Pathway in Parkinson's Disease.

When a patient gets DBS surgery, the neurosurgeon makes a hole in the skull through which they can put the DBS lead down in deep parts of the brain that help control movement. For this study, research participants will also have an ECoG strip put through the same hole (no extra holes are being made for research purposes). The ECoG strip is a little less than half an inch wide, and a little more than 2.5 inches long. It is very, very thin; it is a thin plastic film with flat metal sensors that can record the electrical activity in the brain. The ECoG strips are FDA approved. The neurosurgeon will slide the ECoG strip under the skull but on top of the brain, over another area of the brain that helps control hand/arm movement (motor cortex), so that the study team can record the activity there. The study team will record brain activity from the DBS lead and the ECoG strip simultaneously to try to understand how the brain communicates and sends information. The study team will check that the ECoG strip is in the right place by delivering a very small electrical pulse to the wrist. If the ECoG strip is in the correct location, this electrical pulse will show up on the brain activity being recorded by the sensors in the ECoG strip. Fluoroscopy (i.e. X-ray images that can be taken quickly) will also be done at the end of the surgery to help confirm the location of the ECoG strip. During fluoroscopy, an X-ray beam is used to track a contrast agent ("X-ray dye") through the body, so that the body can be seen in detail. This involves some radiation exposure for the participant, so this is described in the consent form. Patients who want to sign up for the study will not be allowed to do so if they have had other radiation exposures within the past year that would go over a safe limit when added to the amount of radiation expected from the fluoroscopy for this study.

The goal of this study is to understand the relationship between network brain activity and motor signs of Parkinson's disease, and to determine if brain activity can predict optimal locations or network pathways for stimulation. During deep brain stimulation lead placement surgery, research participants will have an FDA approved ECoG strip placed through the DBS lead burr hole over the primary motor cortex. The study team will record brain activity from the DBS lead and the ECoG strip simultaneously while the participant performs a reach-to-target motor task, to understand how different brain regions communicate and are associated with motor signs of Parkinson's disease. The study team will look for specific brain activity biomarkers hypothesized to be associated with Parkinson's disease and will then direct stimulation through the DBS lead toward regions showing those biomarkers and compare to stimulation directed to areas not showing the specified biomarkers. Neural pathways being activated by stimulation and behavioral measures of the reach task will be compared between the two stimulation conditions. Intervention: 1. Stimulation through the DBS lead contact showing the most coherence with brain activity in the motor cortex 2. Stimulation through the DBS lead contact showing the least coherence with brain activity in the motor cortex During the mapping session patients will either be asked to perform motor tasks such as finger-tapping, pronating/supinating the wrist, manipulating a joystick, or pointing to targets on a touch-sensitive, LCD positioned in front of them. Patients may also be asked to perform cognitive tasks such as maintaining items in working memory or deciding between potentially rewarding stimuli with either a joystick or a finger response pad.