Dissertations, Theses, and Capstone Projects

Date of Degree

2-2023

Document Type

Thesis

Degree Name

M.S.

Program

Cognitive Neuroscience

Advisor

Valerie Shafer

Advisor

Lucas Parra

Subject Categories

Cognitive Neuroscience | Computational Neuroscience | Developmental Neuroscience | Discourse and Text Linguistics | Psycholinguistics and Neurolinguistics | Semantics and Pragmatics | Speech and Hearing Science | Speech Pathology and Audiology

Keywords

Event-related potential (ERP), electroencephalography (EEG), discourse coherence (DC), semantic integration (SI), inter-subject correlation (ISC), lateral anterior positivity (LAP), developmental-language disorder (DLD), specific language impairment (SLI), autism spectrum disorder (ASD)

Abstract

Constructing meaning from spoken language is invaluable for learning, social interaction, and communication. In clinical populations with developmental disorders of speech comprehension, the severity of disruption can persist and vary from limiting occupational opportunities to lower performance outcomes. Previous research has reported an event-related potential (ERP) neural positivity over right hemisphere lateral anterior sites in response to semantic and discourse processing. Although useful as a marker for clinical populations of autism spectrum disorder (ASD) and developmental language disorder (DLD), little is understood about the dynamics and neural sources of this biological marker. In addition to traditional methods of ERP analysis, this investigation utilizes methods for analyzing correlated components to determine meaningful sources of neural activity during language processing shared across this population of healthy adults. Based on previously published findings by Neumann et al. (2014), it was hypothesized in the current study that a positivity index of discourse processing would be detected at right lateral anterior sites starting 600 ms after sentence onset and persisting for 300 ms. The current study replicated previous findings and confirms that a persistent positivity is detectable for 300 ms over right lateral anterior sites during late-stage semantic processing. This positivity was shown to be sensitive to word-type in the sentence-initial position, resulting in a 100 ms delay of the LAP response onset time from 700-1000 ms. The results of this analysis also revealed a significant positivity at parietal sites when listening to discourse, which started 1000 ms following sentence onset and persisted for 200 ms. In addition, a significant negativity when listening to discourse over right lateral anterior sites started at 1000 ms following sentence onset and persisted for 200 ms. The results from this study reveal a more complex, biphasic dynamic of potentiation not observed in previous findings which had an epoch limit(ISC) and found to be consistent with the pattern observed for ERPs. The current study confirmed that correlation is stronger for coherent, ordered sentences when compared with randomly-ordered sentences, or with nonsense syllabic speech. These findings suggest a novel understanding of the processes involved in the neural construction of coherent discourse comprehension.

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