Parkinson's disease (PD) is a neurodegenerative disorder in which the substantia nigra has suffered a severe amount of cell loss, resulting in basal ganglia dysfunction. The defining motor symptoms of PD are tremor, rigidity (stiffness of the limbs and trunk), bradykinesia (slow movements), and postural instability (impaired balance). Persons with PD also have a number of non-motor symptoms such as anxiety, depression, autonomic dysfunction, cognitive impairment, and deficits in sensory processing. Currently, there is a gap in our knowledge about how stress affects persons with PD. Anecdotally, many people with PD report that their symptoms get worse when they are stressed. However, there is only indirect and anecdotal evidence for persons with PD. Thus, the purpose of this study was to examine how stress affects motor and non-motor symptoms in persons with PD.

Fifteen persons with PD and fifteen healthy older adults were recruited for the study. We measured how an acute stressor (socially evaluated cold pressor) affected working memory (digit span tasks), sensory processing (inhibitory gating), and PD motor symptoms (UPDRS motor tests). Results showed that stress appears to have differential effects in persons with PD. In persons with PD, stress negatively impacted inhibitory gating and PD motor symptoms. However, stress had positive effects on working memory. The results also suggest that inhibitory gating is associated with PD motor symptom severity, and, thus, inhibitory gating may be a potential therapeutic target. This research provides a first step in understanding how stress impacts persons with PD. Overall, the work of this dissertation suggests that acute stress is a useful tool in understanding PD, and that stress management may be an effective therapy for managing PD motor symptoms.