Non-progressive dysarthria is a speech disorder that affects approximately 480,000 new people per year due to stroke and traumatic brain injury. More severe dysarthria makes speech unusable, severely diminishing quality of life. We have a limited understanding of how processes of speech sensorimotor control are affected by non-progressive brain injury and how control deficits vary by dysarthria severity and type. Consequently, current assessment and treatment approaches are not substantively informed by an understanding of dysarthria-related changes in speech sensorimotor control. The research proposed here aims to broaden our understanding of three processes of speech sensorimotor control: 1) effects of the acoustic task space on articulatory kinematics (auditory-motor mapping); 2) coordination of kinematic redundancy in articulation (mechanical equivalence); and 3) generalization of learning (transfer to the acoustic task space for real speech). We will study these processes in talkers with non-progressive dysarthria and age-matched controls by analyzing the effects of spectral (formant frequency) modifications to auditory feedback on articulatory movements. It is well established that spectral modifications to auditory feedback can be used experimentally to elicit changes in speech movements that illuminate processes of sensorimotor control, but no research has used such an experimental paradigm to study dysarthria secondary to TBI or stroke. We have developed a novel approach for studying speech sensorimotor control that uses articulatory resynthesis, allowing for participants across the severity continuum. Our method converts a participant?s articulatory movements (via electromagnetic articulography) into synthesized, ?virtual speech? in real time to control auditory feedback. Virtual speech training elicits adaptive changes in articulatory movements that generalize to real speech. We will examine these adaptive changes in articulation to bolster our understanding of aspects of sensorimotor control in non-progressive dysarthria. The work has three aims: 1) Characterize baseline articulatory kinematics and determine how they are affected by the size and location of the acoustic ?task? space. 2) Characterize kinematic redundancy (motor equivalence) in the articulatory system and how it is coordinated during adaptive learning. 3) Evaluate how the elements of a virtual speech learning task affect generalization to real speech. This research has vital implications for dysarthria assessment and treatment. The objective is to improve our understanding of auditory-motor integration, mechanical equivalence, and sensorimotor learning in dysarthria. The proposed research promises considerable impact because it examines poorly understood aspects of sensorimotor control in dysarthria that are critical to assessment and treatment.
This research has significant implications for public health, and in particular for the treatment of dysarthria, of which there are nearly half a million new cases annually in the United States. Severe dysarthria is associated with unintelligible speech that severely diminishes quality of life, and current assessment and treatment techniques are not informed by a sufficient understanding of how the brain integrates auditory information to control speech movements. This research will help broaden our understanding of brain function for speech and facilitate improves speech treatments for millions of survivors of brain injury.
