Roozbeh Behroozmand1, Nadine Ibrahim2, Oleg Korzyukov2, Donald Robin3, Charles Larson2
1 Speech Neuroscience Lab, Department of Communication Sciences and Disorders, University of South Carolina, Columbia, SC 29208, United States
2 Speech Physiology Lab, Department of Communication Sciences and Disorders, Northwestern University, Evanston, IL 60208, United States
3 Research Imaging Institute, University of Texas Health Science Center San Antonio, San Antonio, TX 78229, United States
Speech motor control in a highly complex task that requires neural communication between spatially-segregated but functionally-related areas in the brain. The present study investigated the neural correlates of speech motor control by studying the spectro-temporal dynamics of EEG responses when three groups of non-musicians (NM), relative pitch (RP) and absolute pitch (AP) musicians maintained steady vowel sound vocalizations and received pitch perturbations in their voice auditory feedback. We identified two neural response components that highlighted different aspects of auditory feedback processing during vocal pitch motor control. The first component appeared as a phase-synchronized (evoked) fronto-central theta band (5-8 Hz) activity that temporally overlapped with compensatory vocal responses and was significantly stronger in RP and AP compared with NM. The second component was a non-phase-synchronized (induced) frontal delta band (1-4 Hz) activity that had longer onset latency, extended beyond the duration of vocalizations and was stronger in the NM compared with RP and AP. These findings suggest that the evoked theta reflects top-down mechanisms of auditory feedback processing for vocal pitch motor control, and is also a neurophysiological marker of enhanced cognitive ability for pitch processing in RP and AP musicians. However, delta band activity seem to reflect neural processes by which the current state of the sensory-motor networks is updated during an adaptive process that drives subsequent speech motor behavior in response to perturbed auditory feedback. These findings provide new insights to distinctly different neural mechanisms that process auditory feedback for online monitoring and control of vocal pitch during speaking.