This proposal describes a 3 year research translational project program to obtain data that can serve as pilot data in a subsequent submission for a research project grant (R01) by the early stage investigator. The PI is a speech scientist with training in speech signal processing, emotional prosody and prosodic processing, acoustic modeling, and EEG/ERP techniques and is currently working in the area of voice control and motor speech disorders as a postdoctoral fellow at Northwestern University. She will now apply these skills to modeling the neural mechanisms underlying voice control in Parkinson's disease (PD). Environment: The Communication Sciences and Disorders Department at Northwestern University, a research-intensive university and department. As a postdoctoral fellow, the PI will be housed in her mentor's laboratory and has access to space, equipment, and a network of world-renowned scientists. Research: The long-term goal of this research is to understand the neural mechanisms controlling the voice and to extend these findings to people with neurogenic disorders of voice production. The short-term objective is to identify the neurological substrates of impaired vocal control in PD, specifically by testing for abnormal function of the efference copy mechanisms, model the underlying neural circuitry, and compare the results with healthy controls and with a clinical group having diffuse cortical impairment ("impaired controls").
The Specific Aims of the project are: 1) Identify the role of efference copy during voice source identification and error detection/correction in PD and model the neural circuitry and 2) Identify effects of pitch perturbations on volitional F0 modulation and differences in the neural pathways and EEG microstate characteristics. In this experiment, the vocalizations and brain activity (EEG/ERP, microstates) of individuals with Parkinson's disease will be examined when given small perturbations to the auditory feedback of their voice, specifically for the purpose of examining the control system wherein an efference copy of the intended vocal output is compared with the actual sensory feedback. This behavioral-neurological measurement strategy in addition to the sophisticated neurological modeling proposed-including dynamic causal modeling, coherence analysis, and EEG microstate analysis-is a novel approach to examining motor control. Also, the neural mechanisms of voice control that contribute to the voice disorder in PD, including feed forward (fast and automatic control) and feedback control (slow and reliant on sensory feedback) will be defined using a highly innovative paradigm that requires subjects to dynamically change their voice pitch to follow (or shadow) or oppose a pitch shift. Our preliminary data in PD compared to young adults support our hypotheses and warrant further experimentation. The results of these experiments will significantly advance our understanding of auditory feedback on voice control and vocal impairments in PD.
An estimated 90% of individuals with Parkinson's disease (PD) report having voice and speech problems, most often a hypokinetic dysarthria, and yet, current medications to treat common symptoms such as rigidity do not improve voice function. Although PD is known to cause issues in movement control, the cause of vocal symptoms has not been examined as an issue in movement control for voice. This project investigates whether disturbances in the neural network for voice control are at the root of the voice issues in PD and can lead to new avenues for rehabilitation and treatment of vocal symptoms.