Dissertation
The nature of automatic semantic retrieval in individuals with mild cognitive impairment
University of Iowa
Doctor of Philosophy (PhD), University of Iowa
Autumn 2021
DOI: 10.17077/etd.006282
Abstract
The number of people diagnosed with Alzheimer’s disease (AD), a progressive and terminal kind of dementia, continues to rise with an estimated 14 million Americans affected by 2050. Prior to an AD diagnosis, many individuals are diagnosed with mild cognitive impairment (MCI) and have similar, but less severe, symptoms as those with AD. A common occurrence in even the early stages of AD is word finding deficits, which significantly impact effective communication. Semantic priming studies have shown that word finding deficits in AD may partly be due to limitations in the automaticity of semantic retrieval. However, it is unknown if the automaticity of semantic retrieval underlies word finding difficulties in individuals with MCI or if the deficit in semantic retrieval occurs later in the AD continuum.
The current study uses semantic priming to examine the extent to which semantic retrieval is automatic in individuals with MCI in four categories: distinctive attributes (e.g., zebra – stripe), shared attributes (e.g., pigeon – wing), category coordinates (e.g., cat – dog), and abstract words with neutral arousal levels (e.g., motive – reason). Experiments 1 and 2 establish our stimuli in a group of healthy younger and older adults, respectively. Experiment 3 directly compares semantic retrieval in healthy older adults and a group of individuals with MCI.
The results demonstrate that individuals with MCI only show priming on shared attributes when evaluating the raw data. When the data were transformed to control for slowing (a commonly utilized strategy because individuals with MCI are known to have both slower response times and executive functioning deficits), individuals with MCI exhibited priming in three of the four categories (shared attributes, category coordinates and abstract words) which was identical to the healthy older adults in Experiment 2. We found priming for distinctive attributes only in the healthy younger adults. Finally, an exploratory analysis showed individuals with MCI and an additional diagnosis did not exhibit significant priming in any category while those individuals with MCI alone showed priming effects for shared attributes and category coordinates. These findings suggest individuals with MCI exhibit functional automaticity of semantic retrieval on a broad range of word types. However, the presence of additional neurological and/or psychological conditions (not including dementia) negatively impacts the automaticity of semantic retrieval.
Details
- Title: Subtitle
- The nature of automatic semantic retrieval in individuals with mild cognitive impairment
- Creators
- Larissa M. Jordan
- Contributors
- Kristi Hendrickson (Advisor)Karen Bryant (Advisor)Robert Jones (Committee Member)Steven Anderson (Committee Member)Elizabeth Walker (Committee Member)Stewart McCauley (Committee Member)
- Resource Type
- Dissertation
- Degree Awarded
- Doctor of Philosophy (PhD), University of Iowa
- Degree in
- Speech and Hearing Science
- Date degree season
- Autumn 2021
- DOI
- 10.17077/etd.006282
- Publisher
- University of Iowa
- Number of pages
- xiii, 160 pages
- Copyright
- Copyright 2021 Larissa M. Jordan
- Language
- English
- Description illustrations
- illustrations (some color)
- Description bibliographic
- Includes bibliographical references (pages 121-141).
- Public Abstract (ETD)
Individuals with Alzheimer’s disease (AD) have word-finding difficulties which negatively impact efficient and effective communication. A crucial cognitive process that underlies these difficulties is semantic priming, in which semantically related words (e.g., cat and dog) activate one another. Individuals with AD lose their ability to automatically activate some types of semantic relationships. For instance, semantic priming for members of the same category (e.g., cat and dog) and concepts that share attributes (e.g., pigeon and wing) is relatively intact, whereas priming for abstract words (e.g., motive and reason) and distinctive attributes (e.g., zebra and stripe because few animals have stripes) becomes impaired early. Understanding the nature of semantic priming early in the disease progression is crucial as major treatment approaches capitalize on the automatic activation of semantically related words. Investigating semantic priming in individuals with mild cognitive impairment (MCI) – a common precursor to AD – can provide insight into when and to what extent automatic semantic activation becomes impaired.
The current project examines semantic priming in individuals with MCI. During the semantic priming task, participants decided if a letter string was a real English word or not. Four conditions had words with specific semantic relationships (i.e., category coordinates, shared attributes, abstract words, and distinctive attributes) in which the primes and targets were semantically related. Response times for the related and unrelated targets were compared and examined across the four conditions to determine if people with MCI have intact automatic activation of related concepts like healthy older adults do or if they have trouble like individuals with AD do. Results showed that the type of word relationship impacts response times for individuals with MCI as priming occurred for shared attributes, category coordinates, and abstract words. Understanding which words become impaired first can help speech-language pathologists know which word categories to target first when providing treatment.
- Academic Unit
- Communication Sciences and Disorders; Center for Social Science Innovation
- Record Identifier
- 9984210443602771
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