Neurobiological and psychobiological signatures of vocal effort in early career teachers

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Project Summary Muscle tension voice disorders such as primary muscle tension dysphonia (pMTD) are common and can profoundly impact quality of life. Precipitating events such as stress and introverted personality are possible factors in pMTD according to the trait theory of voice disorders. This theory proposed neurobiological mechanisms involving behavioral inhibition, but the condition remains an unclassified voice disorder with unknown causes. Large-scale research into the functional and clinical relevance of stressor-dependent limbic- motor interactions using functional MRI (fMRI) to support a neural basis for pMTD is missing. The aims of the project are to (1) determine the functional relevance of stressor-induced limbic activations on the control of voice in the brain in vocally healthy controls, (2) determine the clinical relevance of stressor-induced limbic activations on the control of voice in the brain in those with and without vocal fatigue, and (3) classify extralaryngeal muscular surface electromyography (sEMG) patterns of stress responders and nonresponders with and without vocal fatigue. Sixty female controls and thirty female early career teachers with vocal fatigue (based on Vocal Fatigue Index) between 21-39 years will read sentences with and without exposure to a speech anticipation stressor using a sparse-sampling event-related fMRI protocol. Salivary cortisol analyses will reveal cortisol stress responders and nonresponders. Participants will wear MRI-compatible sEMG electrodes on the anterior neck and complete a corresponding sEMG speech production protocol, but without stressor exposure, outside the scanner on a separate day. Audio data will be recorded to determine changes in vocal effort during speech production. fMRI activations in the laryngeal motor cortex and functional connectivity of core limbic regions will be determined. Further, sEMG patterns of subgroups will be classified, compared, and the total sEMG data correlated with neural (fMRI), psychobiological (cortisol, personality), and vocal function (acoustic) data for all participants and subgroups. The central hypothesis is that laryngeal stress responders have heightened limbic-motor activations involving the limbic vocalization pathway, which correlate with changes in extralaryngeal sEMG activity. In sum, this innovative project will determine neural, psychobiological, and vocal function signatures of stress responders and nonresponders in early career teachers with vocal fatigue and controls. The results will provide fundamentally missing data in our understanding of the role of stress in vocal complaints and will yield new insights about the neural correlates of pMTD. The study findings will have a significant impact on how we identify laryngoresponders for preventative measures and optimize the long-term success of interventions for a broad range of behavioral voice and speech disorders under consideration of neurorehabilitative interventions such as meditation and transcranial magnetic stimulation and wearable sEMG technology.