Electronic Thesis and Dissertation Repository


Master of Science




MacDonald, Penny A.


Parkinson’s disease (PD) is characterized by resting tremor, rigidity, and bradykinesia. Dopaminergic medications treat motor symptoms, but have complex effects on cognition, including impulse control. Impulsivity is multifaceted in nature. Motor impulsivity involves inability to withhold prepotent, automatic responses whereas cognitive impulsivity refers to increased risk-taking and reward-seeking. We anticipated that dopaminergic therapy would decrease motor impulsivity. We employed the Go/No-go paradigm to assess motor impulsivity. PD patients were tested on and off their dopaminergic medication. PD patients on medication had a significantly higher proportion of Go Timeouts (i.e., Go responses not completed by the 750 millisecond deadline) compared to off medication (p=0.01). We interpret that dopaminergic therapy induces more conservative responding (i.e., decreased motor impulsivity) in PD patients. This contrasts with the widely-recognized notion of dopaminergic therapy increasing cognitive impulsivity and risk of impulse control disorders. Understanding the nuanced effects of dopaminergic treatment in PD will inform clinical decisions.

Certificate of Examination.pdf (303 kB)
Certificate of Examination