Low Frequency Subthalamic Nucleus Deep Brain Stimulation to Improve Verbal Fluency

Evaluation of Neurocognitive Changes in Parkinson's Disease Patients Following Acute Low Frequency Deep Brain Stimulation

Rationale: Parkinson's disease patients with deep brain stimulation electrodes represent a unique opportunity to study the influence of basal ganglia on neurocognitive function.

Intervention: Patients' deep brain stimulators will be turned off or on and the frequency will be changed to either theta or gamma.

Objectives: To identify differences in higher cognitive functions with stimulation "on" and "off" and theta versus gamma frequency stimulation.

Study population: 12 patients who had previously undergone bilateral STN deep brain stimulation implantation.

Study methodology: Patients will undergo four sessions of neuropsychological testing (RNGT, verbal fluency, D-KEFS CWIT) at baseline, no stimulation, theta stimulation and gamma stimulation, in random order over one day.

Study outcomes: Test results of RNGT, verbal fluency, D-KEFS CWIT. Follow-up: none

Statistics: Test results will be analyzed using within-subjects statistical tests.

Inclusion Criteria:

1. Male or female patients who had previously undergone bilateral STN deep brain stimulation implantation
2. Age >18 years old
3. Stable medication regimen for at least 3 months.
4. Patient informed and able to give written consent
5. Able to comply with all testing, follow-ups and study appointments and protocols

Exclusion Criteria:

1. History of epilepsy or seizure
2. History of major substance abuse
3. Patients with baseline settings at less than 1.5 V will be excluded from the study