Author

Yilun Zhang

Date of Award

Fall 2021

Document Type

Open Access Thesis

Department

Statistics

First Advisor

Yuan Wang

Abstract

The complex motor act of speech requires integrating linguistic and sensorimotor processes. Sensorimotor interaction mainly supports speech production in the form of state feedback control architecture. While speaking, subjects react to perturbations in the pitch of voice auditory feedback by changing their tone in the opposite direction to pitch-shift stimuli to compensate for the perceived pitch shift. Aphasia is a communication impairment affecting patients’ speaking, understanding, reading, and writing. The present study aims to examine the association between brain neural activity and the ability for speech auditory feedback error correction in both post-stroke aphasia and neurologically intact individuals. There are 34 aphasic individuals (age: 61+/-11.2 years) and 46 neurologically intact participants (age: 64+/-7.9 years). Participants were asked to produce a vowel sound /a/ under altered auditory feedback (AAF) during the experiment. The vocalization signals were recorded, while EEG signals were simultaneously recorded from 64 scalp electrodes following a standard 10-10 montage. A multivariate linear regression model was fitted to examine the association between the EEG beta band power (13-25 Hz) and the vocal compensation. Results show a significant negative linear association between the two variables under the downward pitch-shift AAF condition. However, such association is not detected for the upward pitch-shift AAF condition. In addition, the aphasia group had significantly reduced power of beta band de-synchronization compared with controls. The findings of the current study reveal that diminished neural de-synchronization of the beta band activities is related to the poorer performance on speech auditory feedback error correction under the downward pitch-shift AAF condition. Such relation is not found under the upward pitch-shift AAF condition. The reason might be that the participants failed to reach the desired low F0 trajectory under the upward pitch-shift stimulus. Furthermore, the beta band de-synchronization is diminished for the aphasia group compared to the healthy control group, suggesting that aphasic individuals have deficits in the underlying neural mechanisms for the sensorimotor system.

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