Neuroimaging studies of audiovocal integration

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The ability to communicate complex thoughts and emotions with speech is uniquely human. As well, it is commonly assumed that the human voice was the first musical instrument. The core skill required for both speaking and singing is the precise coordination of the vocal articulators (larynx, tongue, jaw, and lips). Clinical and experimental evidence indicates that hearing your own voice is important for vocal control. For example, people who lose their hearing after they have learned to talk show a gradual deterioration in the quality of their speech. Problems related to intensity, pitch control and speech rate are frequently seen soon after hearing loss. However, it is only after much longer periods of deafness that problems in vowel and consonant production appear. When hearing impaired individuals can again hear their own speech with the help of technologies such as hearing aids or cochlear implants, the quality of their speech typically returns to normal. This observation that some aspects of speech are immediately affected by deafness while others persist unaltered for a relatively long time after deafness onset shows that some features of speech production rely on auditory feedback, while others rely on a neural representation that allows the brain to predict what sound will result from a particular vocal tract movement. The goal of my research program is to understand how the brain forms and uses these representations of the acoustic-motor relationship for speech. To uncover the neural mechanisms involved, I will use functional magnetic resonance imaging and event-related potential experiments to advance our basic understanding of the sensorimotor mappings that are critical to vocalization. Several communication disorders are thought to be linked to a failure in the mechanisms that relate motor control and sensory feedback. Understanding the sensorimotor representations supporting speech will aid the development of treatments for these forms of communication disorders. In addition, the research may help clarify the impact of hearing impairments on the development of speech in children and the preservation of intelligible speech in adults, as well as be relevant to research on second-language learning.