between the ages of 45 and 85

ability to provide informed consent

patient group: diagnosis of pd, hoehn and yahr stages ii - iv, by a uf movement disorders fellowship trained neurologist having completed a clinical assessment of each participant's pd severity and arriving at the diagnosis of pd by applying strict uf brain bank criteria.

healthy older adults: history of pd, or any other neurologic or neurodegenerative disease including stroke.

history of head and neck cancer, and radiation treatment to the head or neck

history of breathing disorders or diseases (e.g. chronic obstructive pulmonary disease (copd), asthma, lung cancer)

history of smoking in the past 5 years, or for more than 5 years at any one time

severe cognitive deficits including dementia.

difficulty complying with protocol due to severe neuropsychological disorder (i.e., severe depression: 31 or greater on the bdi)