During expressive speech, acoustic stimuli from both self-generated and environmental sound sources are continually processed within the auditory system. This information is used to adjust and optimize speech output through a poorly characterized feedback network. This network is thought to be dysfunctional in a variety of speech disorders, including stuttering, and may be impaired in some patients with psychoses. Despite the importance of this neural system, little is known about how auditory cortex functions when humans vocalize. In this proposal I plan to study this system using invasive experimental methods in epilepsy surgery patient volunteers. By using direct electrophysiologic recording, stimulation techniques, and reversible focal cooling, it is feasible to obtain information about the functional organization of human auditory cortex during vocalization that cannot be obtained using non-invasive methods.
My specific aims are to 1) identify and characterize differences in auditory evoked responses recorded during vocalization and when these vocalizations are played back, 2) characterize how auditory feedback alterations during vocalization changes activity recorded from auditory cortex, 3) test the hypothesis that frontal lobe speech areas are functionally connected to the auditory cortical fields that demonstrate vocalization-induced changes in sound processing, and 4) use a cortical cooling method to reversibly deactivate frontal lobe sites and examine how this affects speech sound processing in functionally connected temporal lobe sites during vocalization. This research will be carried out in the context of a comprehensive career development program. I am fortunate to have experienced and committed mentors who are experts in areas relevant to this project. I also will have full access to the optimal resources needed for conducting human brain physiology research. I will participate in formal coursework, directed study and seminars that will further my objective of acquiring the scientific skills necessary to become an independent neurosurgeon-scientist.
This project will further our understanding of brain mechanisms involved in human vocalization. These mechanisms are poorly understood and may be abnormal in certain speech disorders and psychoses.
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