Modulation of neural responses to naturalistic speech production and perception
Creators: name: Kurteff, Garret
name: 0000-0001-5800-546X
Publisher: name: The University of Texas at Austin
Year: 2020
Subjects: Speech production
Speech perception
Electroencephalography

description: Speech production is under-studied compared to speech perception largely due to complications in data collection caused by articulation. In electroencephalography (EEG), these complications manifest as electromyographic activity (EMG) originating from the muscles that control articulation (Chen et al. 2019). This is unfortunate because EEG is well-suited for studying the rapid temporal changes in speech production. In addition, the few EEG studies of speech production are limited to the single-word level, which limits the generalizability of studies to how speech is used in everyday contexts. In this thesis I present an EEG study of the differences between speech production and perception using sentence-level naturalistic stimuli. Participants overtly produced sentences from the MOCHA-TIMIT (Wrench 1999) corpus then listened to playback of themselves producing the sentences. Perception trials were then split into predictable and unpredictable trials. Predictable trials consisted of playback of the previously produced sentence, while unpredictable trials consisted of playback of a randomly selected previously produced sentence. In this thesis, two contrasts are compared: (1) overt production of sentences versus passive listening to sentences, and (2) passive listening to predictable sentences versus passive listening to unpredictable sentences. Canonical correlation analysis (CCA) was used to remove EMG artifact from the recorded EEG. To demonstrate removal of EMG and preservation of neural responses in CCA-corrected EEG data, event-related potential (ERP) analysis was used on neural responses to perception stimuli, inter-trial click tones, and activity recorded from auxiliary facial EMG electrodes. These ERP analyses revealed a reduction in amplitude for production trials and facial EMG activity after CCA artifact correction and a preservation of early auditory responses in inter-trial click tones, suggesting that EMG was successfully removed while preserving neural responses. After validation of EMG removal, perception and production trials were compared using ERP analysis. Responses to produced sentences were found to have reduced amplitude when compared with perceived sentences, which is consistent with previous research on speaker-induced suppression. Differences in stimulus predictability during speech perception had an effect on response amplitude as well; however, this difference was weaker than the difference in amplitudes observed while comparing the differences between perception and production trials. Multivariate temporal receptive field modeling was used to examine phonological tuning in perception and production. Models demonstrated that speaker-induced suppression does not reflect a change in neural encoding of phonological features but instead a generalized reduction in response amplitude during speech production. Understanding the differences between speech perception and production in a naturalistic context has implications for developing brain-computer interfaces and understanding the neural basis of communication disorders such as apraxia of speech and stuttering. This thesis also serves as a proof-of-concept for studying sentence-level speech production using EEG by demonstrating an effective way of removing EMG artifact while preserving integrity of neural responses.