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Xitong Chen Thesis5.23 MB
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Dissertation
Task representation and cognitive flexibility: neural mechanisms of hierarchical cognitive control and working memory integration
University of Iowa
Doctor of Philosophy (PhD), University of Iowa
Summer 2025
DOI: 10.25820/etd.008115
Abstract
Human behavior is remarkably flexible. People adapt their actions and decisions to changing contexts while integrating multiple sources of task-relevant information. This flexibility depends on task representations, mental representations that encode contexts, stimuli, and responses, to align actions with goals. However, how the human brain constructs and utilizes these representations remains unclear. This dissertation investigates several major questions to determine the neurocognitive architecture supporting task representations. First, how does the brain maintain hierarchically organized task representations, in which higher-level context representations influence actions and decisions, and how does it flexibly update these representations when contexts change? Second, how does working memory integrate multiple sources of information within task representations, including task content (the “what”) with the appropriate rules (the “how”), to generate goal-compatible actions and decisions? Across three studies, this work combines functional neuroimaging, computational modeling, and EEG to examine neural circuits, computational mechanisms, and temporal dynamics underlying task content (the “what”) and task rule (the “how”) representations. First, using fMRI and a hierarchical cognitive control task, we demonstrated that the thalamus encoded context representations within a hierarchically organized task rule, and updated cortical contextual representations via thalamocortical connectivity. Second, computational modeling revealed that the multidimensional “what” representations were integrated in a joint probabilistic manner, and that their formats and properties remained stable across different task rules. This suggests that the “what” system operates independently from the “how” system within working memory. The influence of task rule appears to occur through modulation of the readout of these joint probabilistic representations, rather than altering their encoding formats. Third, EEG evidence further showed that task rules did not affect how the task content was initially encoded but instead modulated neural representations of how that content was maintained and accessed over time, serving as a control signal that routed the “what” representation toward context-appropriate actions and decisions. Together, these findings delineate several specific neural and computational processes—thalamocortical contextual updating, working-memory integration of “what” and “how”, and rule-directed information routing—that translate abstract goals into specific, goal-directed actions.
Details
- Title: Subtitle
- Task representation and cognitive flexibility: neural mechanisms of hierarchical cognitive control and working memory integration
- Creators
- Xitong Chen
- Contributors
- Kai Hwang (Advisor)Jiefeng Jiang (Committee Member)Jan Wessel (Committee Member)Eliot Hazeltine (Committee Member)James Traer (Committee Member)
- Resource Type
- Dissertation
- Degree Awarded
- Doctor of Philosophy (PhD), University of Iowa
- Degree in
- Psychology
- Date degree season
- Summer 2025
- DOI
- 10.25820/etd.008115
- Publisher
- University of Iowa
- Number of pages
- xi, 130 pages
- Copyright
- Copyright 2025 Xitong Chen
- Comment
- This thesis has been optimized for improved web viewing. If you require the original version, contact the University Archives at the University of Iowa: https://www.lib.uiowa.edu/sc/contact/
- Language
- English
- Date submitted
- 05/28/2025
- Description illustrations
- Illustrations, graphs, charts, tables
- Description bibliographic
- Includes bibliographical references (pages 99-115).
- Public Abstract (ETD)
Being flexible in how we think and act is one of the most important mental abilities of human intelligence. The brain supports this cognitive flexibility by building internal mental representations that help us understand what we need to do and how to do it. This dissertation explores the brain and mental processes behind flexible thinking and behavior by asking key questions: How does the brain switch between different rules or situations? How do we hold and combine different pieces of information to make decisions?
Through three studies, we used brain imaging, computational modeling and neurophysiological recordings to answer these questions. The brain imaging studies showed where in the brain this flexibility happened. We found that the thalamus, a deep brain structure with strong connections to other areas, played a key role in updating information about changing situations. The computational modeling study explored how rules guided our use of memory. We discovered that rules did not change how we store information but instead control how we use that information. Finally, neurophysiology recordings, which measure how brain activity changes over time, revealed the timing of these processes, showing that task rules function like a control system that routes stored information to support the right decisions at the right moments.
Together, these studies explain how our brains turn abstract goals into real actions. We showed how different brain and mental systems work together to help us adapt to new situations and solve problems in a flexible, intelligent way.
- Academic Unit
- Psychological and Brain Sciences
- Record Identifier
- 9984948739302771
Metrics
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