Parkinson's disease (PD) is a neurodegenerative disorder involving a part of the brain that is responsible for motor control, which not only results in changes or disruptions in movement, but also cognitive dysfunctions. Given that the decline of muscle control such as tremors, with difficulty walking or the ability to switch tasks once in movement, greatly affects the quality of daily life. Action regulation is a critical executive function (cognitive control over behavior), which includes actions such as suppressing activity when selecting between options, making decisions about stopping unwanted or inappropriate actions, and switching to new actions in response to environmental changes. Parkinson's disease (PD) has been shown to disrupt action inhibition which can be considered a measure to the progression of PD.

The purpose of this research study is to better understand the mechanism of action regulations in PD patients and how action regulations in PD can be improved using dopaminergic treatment, which is a drug that either releases or involves dopamine, which is a neurotransmitter involved in sending signals to nerve cells.

You are asked to participate in this research study because you are receiving a dopaminergic medication for treatment of your Parkinson's disease. There is currently no theory that integrates the mechanisms of action regulation into a unified framework, which this study aims to address. The researchers hope to learn more about the mechanisms of action regulation in PD patients and to help decrease action regulation disruptions in PD patients. This study will help characterize the motor behavior of PD patients.

For Parkinson's Disease Patients:

Inclusion Criteria:

• Diagnosis of Parkinson's Disease by a movement disorder neurologist
• Levodopa responsive with clearly defined "on" periods, with at least 30% improvement in UPDRS III scores on vs off
• Willingness and ability to complete the behavioral experiments for up 3.5 hours
• No vision or hearing problems that impair ability to participate with the proposed tasks as assessed by the study investigators

Exclusion Criteria:

• Patients with history of secondary Parkinsonism, stroke, or progressive central nervous system disease other than Parkinson's Disease
• Patients with a disease or condition that prevents understanding or communication of informed consent, study demands, and testing protocol including cognitive decline, diagnosed forms of dementia, significant memory impairment (MoCA<23), or hearing loss that prevents adequate communication with researcher

For Healthy subjects:

Inclusion Criteria:

• No history any diagnosed neurological disease(s), including movement disorders or cognitive decline
• No vision or hearing problems that impair ability to participate with the proposed tasks as assessed by the study investigators

Following data acquisition, de-identified data will be shared with research team at University of California, Riverside.