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Scholarly Works (3 results)

  • Article
  • Peer Reviewed
Proceedings of the Annual Meeting of the Cognitive Science Society, Volume 44 (2022)
The free recall of triadic comparisons, a task used in clinical settings, presents a unique analysis challenge for many memory models, because learning occurs incidentally and items are presented multiple times in triads. To account for this design, we extend the SIMPLE (Brown et al., 2007) model of memory, which assumes to-be-remembered items are stored as separate logarithmically-compressed temporal traces. The ability to retrieve these traces depends on the acuity of memory probes and the semantic similarity between the items represented by the traces. We applied this model to a real-world clinical data set including healthy controls, people with mild cognitive impairment (MCI), and people with Alzheimer’s dementia. We found that people with MCI had lower acuity than healthy controls, but both groups placed roughly equal weight on temporal and semantic cues. People with dementia had both lower acuity and placed much more weight on temporal cues than semantic cues.
    Cover page: A model of free recall for multiple encounters of semantically related stimuli with an application to understanding cognitive impairmentCreative Commons 'BY' version 4.0 license
    • Article
    • Peer Reviewed
    Proceedings of the Annual Meeting of the Cognitive Science Society, Volume 43 (2021)
    Alzheimer’s disease leads to a decline in both episodic and semantic memory. Free recall tasks are commonly used in assessments designed to diagnose and monitor cognitive impairment, but tend to focus only on episodic memory. Our goal is to understand the influence of semantic memory on the sequence of free recall in a clinical data set. We develop a cognitive process model that incorporates the influence of semantic similarity and other stimulus properties on the order of free recall. The model also incorporates a decision process based on the Luce choice rule, allowing for different levels of response determinism. We apply the model to a real-world data set including free recall data from 2392 Alzheimer’s patients and their caregivers. We find that semantic similarity between items strongly influences the order of free recall, regardless of impairment. We also observe a trend for response determinism to decrease as impairment increases.
      Cover page: A Model-Based Analysis of Changes in the Semantic Structure of Free Recall Due to Cognitive ImpairmentCreative Commons 'BY' version 4.0 license
      • Thesis
      • Peer Reviewed
      UC Irvine Electronic Theses and Dissertations (2023)

      It is well established that Alzheimer’s disease leads to a decline in both episodic and semantic memory. My research focuses on semantic memory and uses cognitive models to try to understand the nature of changes in memory as the disease progresses. Applying cognitive models, I am able to make inferences about underlying memory processes that cannot be measured directly from behavioral data.

      In Chapter 1, I evaluate theories of the change in semantic memory caused by Alzheimer's disease. Many such theories characterize the cognitive decline associated with Alzheimer’s disease as an elaborate combination of systematic changes to underlying mental representations and to attention processes. I conclude that a simpler theory of Alzheimer’s disease as interfering with the patient’s ability to retrieve information stored in memory can account for the data just as well as more complex theories.

      In Chapter 2, I investigate changes in episodic memory associated with Alzheimer’s disease. I specifically focus on the order of free recall among Alzheimer's patients and develop a regression model that includes semantic similarity and various word-level characteristics as predictors. I demonstrate that the semantic similarity between items and the number of times an item is encountered are potentially important predictors of free recall output.

      In Chapter 3, I explore how semantic memory can influence episodic memory recall. I extend the SIMPLE model of memory and apply it to three groups of patients including healthy controls, people with mild cognitive impairment, and people with Alzheimer’s dementia. I compare and contrast the relative influence of temporal similarity and semantic similarity on free recall performance within the three patient groups. As cognitive impairment increased, the ability to distinguish between items that were temporally similar decreased, as did the use of semantic similarity as a recall cue.

      Collectively, the work in this dissertation shows that cognitive models of memory can provide a more complete understanding of the changes in semantic memory that occur with cognitive impairment.

        Cover page: Using Memory Models to Understand Cognitive Impairment Associated with Alzheimer's Disease
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