Director: Kristie Spencer, Ph.D.   Parkinson's Disease People with Parkinson's disease (PD) are thought to have difficulty maintaining prepared movements/thoughts, as well as switching between movements and thoughts. What are the underlying processes that may contribute to these symptoms of Parkinson's disease? Are cognitive, linguistic and/or motor programming abnormalities adding to the known difficulties with motor execution? This research uses speech and manual reaction time protocols, and robust "priming" patterns, to try to understand the difficulties with maintenance and transitioning in people with PD.          Cerebellar Disease Do people with ataxic dysarthria from cerebellar disease have difficulty with speech motor programming in addition to motor speech execution? The dysarthrias have traditionally been thought to result from a disruption of motor execution, with little attention given to the preparatory processes of speech production. One particular aspect of speech preparation that merits consideration is motor programming, or the process of transforming linguistic-symbolic representations into a motor code. The cerebellar circuit in particular is known to be involved in this motor programming process. This research uses a speech reaction time protocol and the well-known sequence-length effect to begin to understand the potential contributions of motor programming disruption to ataxic dysarthria.