In this study, the investigators aim to investigate the effects of non-invasive neurostimulation - low-intensity transcranial electrical stimulation in conjunction with transcranial ultrasound (TUS)- on the motor symptoms associated with Parkinson's disease. The investigators want to see if there is a difference between active and sham stimulation on these motor symptoms.

Inclusion Criteria:

• Documentation of PD diagnosis from their clinician by either a letter or verification through their medical record
• Research criteria of "possible" or "probable" PD, as defined by Gelb et al (Gelb D, Oliver E, Gilman S. Diagnostic Criteria for Parkinson Disease. Arch Neurol.1999;56:33-39)[1]
• Age 40 or over;
• Taking stable medications for at least 30 days

Exclusion Criteria:

• Features suggestive of other causes of parkinsonism/Parkinson's-plus syndromes;
• History of deep brain stimulation or ablation surgery, mass brain lesions;
• History of schizophrenia, schizoaffective disorder, other psychosis, episode of bipolar illness, alcohol/drug abuse within the past year;
• Need for rapid clinical response due to conditions such as initiation, psychosis, or suicidal;
• Contraindications to transcranial brain stimulation or TUS, i.e. metal in the head, implanted brain medical devices, etc;
• Unstable medical conditions (e.g. uncontrolled diabetes, uncompensated cardiac issues, heart failure, pulmonary issues, or chronic obstructive pulmonary disease);
• Pregnancy.
• Epilepsy or disorders that increase likelihood of seizures including: moderate or severe traumatic brain injury, congenital birth defects leading to seizures, brain tumor, metabolism disorders associated with seizures, and nonlacunar stroke.