Cholinergic Neurotransmission in Mobility and Cognition in Parkinson Disease

This is a single-site non-randomized open label pilot study. The investigators will use accelerometer-based instrumented gait analysis and computerized cognitive testing to study the interaction of motor and cognitive dysfunction in Parkinson disease dementia (PDD), and the effect of rivastigmine on motor and cognitive performance. All study participants will be tested for motor and cognitive performance at baseline (arm 1). A subgroup of study participants will then be treated with rivastigmine for 12 weeks (arm 2), and the effect of this treatment on gait measures and cognitive measures will be analyzed at the follow-up visit 12 weeks after the baseline visit. Specifically, we will determine which components of motor and cognitive impairment are associated with each other, and which components of the two domains respond to rivastigmine-mediated stimulation of cholinergic neurotransmission.