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Author Fredericks, Geoffrey Vincent
Title An electrophysiological investigation into semantic processing in aphasia
book jacket
Descript 175 p
Note Source: Dissertation Abstracts International, Volume: 63-07, Section: B, page: 3267
Chair: Scott S. Rubin
Thesis (Ph.D.)--University of South Alabama, 2002
The focus of this study was to investigate both lexical and nonlexical semantic processing in people with aphasia, and the semantic system in general. A total of eight participants were included in this study, and were divided into three groups: a low comprehension aphasia group, a high comprehension aphasia group, and a normally aging elderly adult control group. Participants were tasked with passively viewing semantically related and semantically-unrelated lexical and picture pairs, with event-related potential data collected from seven electrode sites (Fz, Cz, Pz, F3, F4, P3, P4). Results from this study were analyzed using both the electrode means, and data from the three midline sites for the measures of N400 (1) onset latency, (2) peak latency, and (3) peak amplitudes in response to the presentation of both nonlexical (picture) and lexical stimuli. Results included significant differences between the high comprehension aphasia group and the normally aging elderly adult group for the N400 measures of onset and peak latency in response to lexical stimuli. In addition, we identified multiple other N400 comparisons with large practical significance, as highlighted by effect size indicators. Results were discussed in relation to previous ERP findings in aphasia research, and generally supported the notion that lexical-semantic processing is impaired in aphasia. Further, it was suggested that the time course for the semantic processing of nonlexical information may also be disrupted in aphasia. Additionally, results were interpreted with regard to the structure of semantic memory as either a unimodal or multimodal system
School code: 0491
Host Item Dissertation Abstracts International 63-07B
Subject Health Sciences, Speech Pathology
Alt Author University of South Alabama
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