Using Neuroimaging to Test Models of Speech Motor Control

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To speak so a listener understands, the speaker has to accurately produce the sounds from his or her language. While this may seem effortless for most people, the actual speech production involves complex mental and physical processes involving the activation of speech muscles and the precisely timed movements in the vocal tract (e.g., the combination of movements in the mouth, jaw, and so on). The unique properties of the individual's speech organs (e.g., size of mouth), combined with the developmental changes of these properties over a lifetime, will directly influence the way speech sounds are produced by each individual. How does the human brain accomplish this feat of continually tuning the control of vocal tract so that it always produces the sounds desired? With support from the National Science Foundation, the investigators will study how the speaking process involves the brain predicting the sensory feedback and correcting the control of the vocal tract when the feedback does not match the prediction. While previous research suggests that this prediction and correction process does occur during speaking, there is little information about how the circuitry in the brain would accomplish such a process. In the proposed research the investigators will examine the timecourse of neural responses to audio feedback perturbations (brief changes in pitch, amplitude, or formant frequencies) during speaking. They will use magnetoencephalography (MEG) and electrocorticography (ECOG) methods to record normal individuals and epilepsy patients who have electrodes implanted in their brain to localize seizures. Both methods allow neural activity in the brain to be recorded at a millisecond time resolution.The results of these experiments will allow for the testing of different models that have been proposed to explain the neural substrate of speech motor control. The outcome of the research will facilitate relating the control of speaking to what is known in other domains of motor control research, and lead to a more complete understanding of the control of movements in humans. The use of advanced functional neuroimaging to study the neural basis of speaking will provide a special opportunity to train and educate a wide range of graduate students, post-doctoral trainees, and medical students who will get involved in the research. The proposed research will also further the development of multi-user research facilities, especially at the UCSF Biomagnetic Imaging Laboratory that has one of a limited number of MEG scanner facilities in the US.