Theses and Dissertations from UMD

Permanent URI for this communityhttp://hdl.handle.net/1903/2

New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM

More information is available at Theses and Dissertations at University of Maryland Libraries.

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Author: search.filters.author.Lei, Yuqing

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    MULTIMODAL ANALYSIS OF NEURAL SIGNALS RELATED TO SOURCE MEMORY ENCODING IN YOUNG CHILDREN
    (2024) Lei, Yuqing; Riggins, Tracy; Psychology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The emergence of source memory is an important milestone during memory development. Decades of research has explored neural correlates of source memory using electroencephalography (EEG) and functional magnetic resonance imaging (fMRI). However, connections between findings from the two approaches, particularly within children, remain unclear. This dissertation identified fMRI-informed cortical sources of two EEG signals during memory encoding, the P2 and the late slow wave (LSW), that predicted subsequent source memory performance in a sample of children aged 4 to 8 years. Both P2 and LSW were source localized to cortical areas of the medial temporal lobe (MTL), reflecting MTL’s crucial role in both early-stage information processing and late-stage integration of memory, which also validated LSW’s suspected role in memory updating. The P2 effect was localized to all six tested subregions of cortical MTL in both left and right hemispheres, whereas the LSW effect was only present in the parahippocampal cortex and entorhinal cortex. P2 was additionally localized to multiple areas in the frontoparietal network, a cortical network known as the “attention network”, highlighting interactions between memory encoding and other cognitive functions. These results reflect the importance of considering both spatial and temporal aspects of neural activity to decode memory mechanism, and demonstrated the potential of combining multimodal measures in children, paving the way for future developmental research.
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    Conflict and Competition between Model-based and Model-free Control
    (2020) Lei, Yuqing; Solway, Alec; Psychology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    There are two learning systems behind human decision-making: the model-based (MB) system and the model-free (MF) system. While they both contribute to decision-making behaviors, it is not clear how the two systems interact to formulate a single decision, especially when they are in conflict. This present thesis defines decision conflict between the systems in two popular binary-choice tasks: Daw’s Two-step task and Kool’s Rocket Task. We used hierarchical modeling to identify conflict-related changes during decision process using the Drift-Diffusion Model (DDM). Evidence showed that the MB system compromises when there is a conflict with the MF system, whether the conflict is on the valuational level or action level. We also looked at how a key component of obsessive compulsive disorder (OCD), the cognitive self-consciousness (CSC), affects the two learning systems during decision.