Date of Degree
MA (Master of Arts)
Speech Pathology and Audiology
Jean K. Gordon
First Committee Member
Karla K McGregor
Second Committee Member
Melissa C Duff
Verbal communication relies heavily on the ability to effortlessly produce intended words to express a meaning. This capacity is frequently impaired in individuals with aphasia, and impairment often lasts well into the chronic stages. However, the nature of anomia can vary. Phonological neighborhood density (PND) is one feature of words which has been shown to impact the ease of retrieval in speakers with aphasia; words with more similar-sounding neighbors are easier to retrieve because the neighbors help activate the target. However, it is unclear how different types of lexical access breakdowns affect the impact of PND. The aim of this project was to analyze the relationship between word retrieval accuracy, speech error patterns, and PND in individuals with aphasia. Twenty-two participants with various types and severities of aphasia named 200 single-syllable line drawings. WebFit, an online software program designed to fit naming data to a theoretical model of word retrieval, was used to characterize participants' error patterns by calculating the strength of connections within the lexicon, as well as the rate of decay. Analyses confirmed previous findings that participants with all types of breakdown achieved lower rates of overall accuracy. Weaker connections between semantic knowledge and words resulted in a more errors that were close to the target, relative to errors with no relationship to the target. Individuals with more severe impairments of the semantic-lexical connections and the lexical-phonological connections produced words with many neighbors more accurately than words with fewer neighbors. Implications for initial therapy target selection and directions for further research are discussed.
Being able to think of and speak the words one wants to say is critical for timely, effective communication, and it is an ability that comes effortlessly to most of us. However, in speakers with aphasia, a language impairment due to a stroke, word retrieval difficulties (anomia) are very common, and tend to last long after the onset of the stroke. The nature of word retrieval difficulty also varies in different types of aphasia. In order to maximize the success of speech-language therapy for these individuals, it is important to understand a variety of factors which influence how easily and quickly individuals can produce words. According to one model of word retrieval, anomia is due to weakened connections within the individual’s mental store of words, resulting in speech errors. According to previous research, words with more “neighbors” (similar-sounding words, such as “bee”), appear to be easier to produce than words which are more unique in sound, such as “glove”. However, it is unclear if individuals with different breakdowns in the word retrieval process experience different effects when attempting to produce words with many neighbors compared to words with few neighbors. The aim of this project is to analyze the effect of word neighbors on naming accuracy in individuals with aphasia and different types of word retrieval breakdown. Twenty-two participants with various types and severities of aphasia named 200 single-syllable line drawings. The speech errors they made were categorized and analyzed. Word retrieval was difficult for individuals with all types of breakdown, but differences were found in the patterns of errors produced and the extent to which word neighbors facilitated production. Ways in which this information can improve treatments for anomia are discussed.
publicabstract, Aphasia, Phonological neighborhood density, Word retrieval
viii, 47 pages
Includes bibliographical references (pages 44-47).
Copyright 2015 Arianna Paige Morgart
Morgart, Arianna Paige. "Lexical access in aphasia: impacts of phonological neighborhood density on accuracy of word production." MA (Master of Arts) thesis, University of Iowa, 2015.