Dissertations, Theses, and Capstone Projects

Date of Degree

6-2023

Document Type

Dissertation

Degree Name

Ph.D.

Program

Speech-Language-Hearing Sciences

Advisor

Loraine Obler

Committee Members

Peggy Conner

Nancy Eng

Subject Categories

Other Rehabilitation and Therapy | Psycholinguistics and Neurolinguistics

Keywords

Aphasia, Lexical Retrieval, Semantics, Nouns, Connected Speech, Speech Therapy

Abstract

Nearly all people with aphasia (PWA) report difficulty with lexical retrieval (i.e., anomia). While there are several tasks used to measure lexical retrieval, each poses different degrees and types of challenges. For example, some studies have found that PWA performance varies depending on the type of lexical retrieval task. The tasks that have been used include lexical retrieval in isolation tasks (such as picture-naming), lexical retrieval in sentence level tasks (such as narration tasks), and lexical retrieval in sentence-completion tasks. Some studies have found no differences between the accuracy of lexical retrieval in isolation and at the sentence level (e.g., Basso, Razzano, Faglioni, and Zanobio, 1990), while others note evidence that lexical retrieval at the sentence level is more efficient than lexical retrieval in isolation (e.g., Pashek and Tompkins, 2002). Even within a study, there is inconsistency as to which task is more difficult. Pashek & Tompkins (2002) used the same stimuli across multiple tasks and found that not all PWA were more accurate on the picture naming task, consistent with differences noted in an earlier study by Williams and Canter (1982).

When comparing lexical retrieval in isolation versus at the sentence level, the task demands naturally differ, thus providing different semantic and syntactic contexts for the target. The current study investigated the role of linguistic information on single word retrieval by manipulating syntactic and semantic information; that is, whether visual, semantic and syntactic contexts offer different levels of support for word retrieval in healthy controls and people with aphasia. We examined two different types of visual stimuli (images with associated verbs and isolated images), task demands, and the role of a related verb in sentence completion tasks in the two groups of individuals. Participant performance was evaluated for both accuracy and response time for a more detailed analysis.

Our findings show differential performance between people with aphasia and healthy controls across experimental tasks: specifically, healthy controls tended to have more uniform performance for both accuracy and response time, while individuals with aphasia showed variability. Semantic content in visual images was both facilitative and inhibitory depending on the population and order of presentation, while auditory semantic content appears to be facilitatory in healthy controls. Previous research on sentence level lexical retrieval is supported for healthy controls, and inconclusive for individuals with aphasia. This study provides valuable information about the role of semantic and syntactic information in lexical retrieval. Healthy individuals are aided in lexical retrieval with both a syntactic frame and semantically related verbs, while individuals with aphasia show a great deal of variability. The findings further highlight the need for future research regarding individual factors that may impact conflict resolution in lexical retrieval in acquired brain injury populations.

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