A critical feature in the development of speech production models has been the capacity of the system to compensate rapidly for perturbations in the dynamic state of the orofacial structures. This ability has led some investigators to propose that speech motor control, like many other motor behaviors, is generative, continuously adapting to system dynamics within the limits of physiologically determined constraints. Pathological speech production due to sensorimotor deficit (i.e. dysarthria) might be modeled as the result of a change in those constraints, and therapeutic intervention might consequently be designed within that altered set. The specific objectives of the present investigation are to determine whether or not any changes in the motor organization of jaw movement occur in dysarthric speakers, and to evaluate the effects of therapeutic treatment in terms of promoting coordinative reorganization. In a larger sense this investigation is intended to determine whether or not the speech motor control system is capable of reorganization in response to alterations in the sensorimotor machinery. Furthermore, the ability of a speaker to change coordinative organization on the basis of therapeutic feedback will be assessed. These objectives will be addressed by quantifying jaw muscle coordination in speakers with Parkinsons's disease before and after a course of treatment for dysarthria. Jaw muscle activity will be recorded electromyographically and subjected to cross-correlational analysis to quantify patterns of activity among the jaw muscles. Mandibular kinematics and acoustic output will also be recorded and analyzed for changes following therapeutic treatment.