Cortical Electrophysiology of Response Inhibition in Parkinson's Disease

DRUG

Levodopa

Participants will take levodopa in dosages prescribed by their care provider. Patients will be instructed to not take their regularly prescribed PD medications for 12 hours prior to the study assessment, as is typical for clinical evaluations in patients with PD. Participants will be tested in both levodopa-off (after 12 hours of not having medication) and levodopa-on states.

DEVICE

Clinical DBS Setting

Deep brain stimulation performed with the patients' optimized clinical setting.

DEVICE

Sham DBS

Deep brain stimulation performed with sham stimulation.

DEVICE

DBS Setting Maximizing Prefrontal Activation

Deep brain stimulation performed to maximize the activation of the prefrontal cortico-STN projections.

DEVICE

DBS Setting Minimizing Prefrontal Activation

Deep brain stimulation performed to minimize the activation of the prefrontal cortico-STN projections.

Response Time During Go/No-Go (GNG) Task for Participants in Aim 1

Time frame: Day 1 (before and after levodopa dosage for persons with PD)

The GNG task is a tool for measuring impulsiveness by asking participants to respond to a cue signal for pressing a button. There are Go trials, where the button should be pressed, and No-Go trials, where the button should not be pressed. A total of 240 trials will be administered (5 blocks of 30) after an initial practice block (12 trials). An additional 120 Go only trials will be administered prior to the Go/No-Go blocks and serve as a control without inhibitory demands. Participants with PD attend a single study visit, completing this task twice: once after not taking PD medications for 12 hours and again after levodopa dosage. Healthy controls complete the task twice during one study visit. Response time is measured in milliseconds (ms) during the GNG task.

Percent of Errors During Go/No-Go (GNG) Task for Participants in Aim 1

Time frame: Day 1 (before and after levodopa dosage for persons with PD)

The GNG task is a tool for measuring impulsiveness by asking participants to respond to a cue signal for pressing a button. There are Go trials, where the button should be pressed, and No-Go trials, where the button should not be pressed. A total of 240 trials will be administered (5 blocks of 30) after an initial practice block (12 trials). An additional 120 Go only trials will be administered prior to the Go/No-Go blocks and serve as a control without inhibitory demands. Participants with PD attend a single study visit, completing this task twice: once after not taking PD medications for 12 hours and again after levodopa dosage. Healthy controls complete the task twice during one study visit. Accuracy is measured as the percentage of errors during the GNG task.

Stopping Time During Modified Stop Signal (MSS) Task for Participants in Aim 1

Time frame: Day 1 (before and after levodopa dosage for persons with PD)

For the MSS task, a fixation cross indicates the start of a trial. After a variable delay (300-700 ms) this signal is replaced by a green Go signal circle, prompting the subject to start to make circling movements with a computer mouse at approximately one rotation per second using dominant hand. After 500 ms the green circle is replaced by a visual countdown to when a red Stop signal appears (planned stop). In 50% of the trials, the Stop signal appears unexpectedly during the countdown (unplanned stop). A total of 120 trials will be administered (10 blocks of 12). Participants with PD attend a single study visit, completing this task twice: once after not taking PD medications for 12 hours and again after levodopa dosage. Healthy controls complete the task twice during one study visit. Stopping time is measured in milliseconds.

Response Time During Go/No-Go (GNG) Task for Participants in Aim 3

Time frame: Up to 12 months post-implantation of DBS leads

The GNG task is a tool for measuring impulsiveness by asking participants to respond to a cue signal for pressing a button. There are Go trials, where the button should be pressed, and No-Go trials, where the button should not be pressed. A total of 240 trials will be administered (5 blocks of 30) after an initial practice block (12 trials). An additional 120 Go only trials will be administered prior to the Go/No-Go blocks and serve as a control without inhibitory demands. Participants with PD attend two study visits, within a 4-week period, at 6 to 12 months after implantation of the DBS leads. Participants will not take PD medications for 12 hours prior to the study visit. During each study visit chronic DBS will be turned off and two stimulation settings will be tested at each study visit so that participants all four stimulation settings over the two study visits. Response time is measured in milliseconds (ms) during the GNG task.

Percent of Errors During Go/No-Go (GNG) Task for Participants in Aim 3

Time frame: Up to 12 months post-implantation of DBS leads

The GNG task is a tool for measuring impulsiveness by asking participants to respond to a cue signal for pressing a button. There are Go trials, where the button should be pressed, and No-Go trials, where the button should not be pressed. A total of 240 trials will be administered (5 blocks of 30) after an initial practice block (12 trials). An additional 120 Go only trials will be administered prior to the Go/No-Go blocks and serve as a control without inhibitory demands. Participants with PD attend two study visits, within a 4-week period, at 6 to 12 months after implantation of the DBS leads. Participants will not take PD medications for 12 hours prior to the study visit. During each study visit chronic DBS will be turned off and two stimulation settings will be tested at each study visit so that participants all four stimulation settings over the two study visits. Accuracy is measured as the percentage of errors during the GNG task.

Stopping Time During Modified Stop Signal (MSS) Task for Participants in Aim 3

Time frame: Up to 12 months post-implantation of DBS leads

For the MSS task, a fixation cross indicates the start of a trial. After a variable delay (300-700 ms) this signal is replaced by a green Go signal circle, prompting the subject to start to make circling movements with a computer mouse at approximately one rotation per second using dominant hand. After 500 ms the green circle is replaced by a visual countdown to when a red Stop signal appears (planned stop). In 50% of the trials, the Stop signal appears unexpectedly during the countdown (unplanned stop). A total of 120 trials will be administered. Participants with PD attend two study visits, within a 4-week period, at 6 to 12 months after implantation of the DBS leads. Participants will not take PD medications for 12 hours prior to the study visit. During each visit chronic DBS will be turned off and two stimulation settings will be tested so that participants all four stimulation settings over the two study visits. Stopping time is measured in milliseconds.

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Will I receive a placebo instead of treatment?

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