Testing magnetic brain stimulation for mild thinking difficulties

Inclusion Criteria: * 50-85 years of age * Diagnosis of Parkinson's disease based on UK Brain Bank diagnostic criteria * Parkinson's disease with mild cognitive impairment (PD-MCI) diagnosis per Movement Disorders Society Task Force Level II Diagnostic Criteria4 (i.e., scores ≥1.5 standard deviations below appropriate norms on 2 neuropsychological tests) as determined by a clinical neuropsychologist * Stable on Parkinson's disease medications for 30 days (not expected to change through the course of the treatment) * Has a caregiver willing and able to reliably complete a questionnaire focused on the participant's daily functioning Exclusion Criteria: * Claustrophobia or inability to lie supine in the scanner for an extended period of time * Barriers to making contact between the TMS coil and the skin (e.g. braids that cannot be removed) * Contraindications to MRI/TMS safety screening: This includes but is not limited to implanted medical devices (e.g., pacemakers), metallic objects or fragments, non-removable hair clips or piercings, and medications that reduce seizure threshold. * Individuals with a diagnosis of bipolar disorder, schizophrenia, and/or active substance abuse disorder. * History of significant or unstable condition/s or treatments for these condition/s that may impact cognition (as determined by the study investigators) such as significant cardiac (e.g. heart failure), infectious (e.g. HIV, urinary tract infection), or metabolic disease (e.g. labile diabetes), cancer (e.g. brain cancer, chemotherapy-induced cognitive impairment), developmental disorder (e.g. autism spectrum disorder, intellectual disability), or other neurologic disease (e.g. multiple sclerosis, moderate to severe brain injury, seizures). * History of a seizure disorder.