Enhancing speech motor learning using visual biofeedback

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The ability to produce speech sounds depends critically on sensory input (how it sounds and feels) to provide talkers with information about the success or failure of their speech actions. This has been explored experimentally in numerous studies by manipulating sensory feedback in real-time (e.g., altering the speech acoustic signal) and measuring the degree to which talkers compensate for perceived sensory errors. The vast majority of these studies report successful speech learning following a brief, intense practice period, however the degree of adaptation is typically small and variable among subjects. Surprisingly, very little attention has been given to procedures or conditions that may serve to enhance the rate, extent, and generality of sensory-based speech learning. The proposed research program builds directly on my prior NSERC-funded research by exploring a number of specific ways in which speech motor learning might be enhanced, with a focus on enrichment of the sensory signals available to talkers during speech production. Central to this research is the use of visual biofeedback, which provides talkers with real-time information about critical aspects of speech that are typically outside of their conscious awareness and control. Two types of visual biofeedback will be explored: 1) using ultrasound to provide a real-time image of the tongue in the mouth, and 2) providing a simplified, real-time visual representation of the sound of speech. Visual biofeedback has recently shown promise as a potential clinical treatment for speech disorders in children and adults. To date, however, there has been a near complete lack of basic, systematic research on the mechanisms of speech learning that are presumed to underlie its use. Here, different forms of visual biofeedback will be examined in highly controlled speech learning tasks, using training procedures developed using principles of motor learning (established outside the domain of speech), in order to improve speech learning outcomes. The specific aims are to 1) explore how the presentation of visual biofeedback may be optimized during different speech tasks to maximize performance, retention and generalization of learning, 2) examine how individual talkers differ in their ability to use visual biofeedback during speech learning, and whether such differences relate to the accuracy of their sensory abilities (auditory and tongue-tactile), and 3) explore whether the ability to use visual biofeedback during speech learning is limited in younger children compared with older children and adults. Identifying conditions that can reliably increase the success of speech motor learning will not only teach us more about the brain's mechanisms for speech motor learning and control, but will provide a clear basis for improving such learning in real-world contexts, including the production of speech sounds in a new language, and in the behavioural treatment of speech disorders.