Dissertations, Theses, and Capstone Projects

Date of Degree

6-2023

Document Type

Dissertation

Degree Name

Ph.D.

Program

Psychology

Advisor

Elizabeth Chua

Committee Members

Jennifer Mangels

Tatiana Aloi Emmanouil

Laura Rabin

Anjali Krishnan

Subject Categories

Cognitive Neuroscience

Keywords

Metamemory, tDCS, HD-tDCS, DLPFC, Semantic Memory, Episodic Memory

Abstract

Metamemory, broadly defined as knowledge about one’s own memory, is thought to consist of two separate processes, monitoring, the ability to assess the contents of your own memory, and control, altering behavior in service of memory, that work together to aide in encoding and retrieval processes. Prior work has shown that metamemory monitoring accuracy can be improved in a semantic memory task via high-definition transcranial direct current stimulation (HD-tDCS), a form of non-invasive brain stimulation, over the left dorsolateral prefrontal cortex (DLPFC). Over three experiments, the current dissertation sought to replicate and extend this work by: 1) testing the effects of HD-tDCS over the DLPFC in memory and metamemory monitoring for an episodic memory task, 2) testing of the effects of conventional tDCS over the DLPFC in memory and metamemory monitoring for both a semantic and episodic task using remotely supervised (rs) tDCS, 3) using HD-tDCS to examine the role of the DLPFC in memory and metamemory monitoring and additionally metamemory control. There were some effects of brain stimulation on memory performance, with greater cued recall when HD-tDCS was applied over the DLPFC right before cued recall compared to sham. Additionally, there were rs-tDCS induced improvements in recognition accuracy, but only in certain task orders. However, across three experiments there was no evidence that either HD or conventional rs-tDCS over the left DLPFC results in improved metamemory monitoring accuracy. A follow-up behavioral study suggested that, in one experiment, the lack of improvement in metamemory monitoring accuracy was related to changes made in the behavioral task. Turning to metamemory control, there were no effects of brain stimulation, but there was evidence that individuals use their metamemory monitoring judgments to control their memory. Although there were some interesting findings, there were mostly null effects of tDCS, suggesting a need for more systematic testing of tDCS as an experimental tool, specifically regarding the parameters in which tDCS does and does not produce changes in cognition.

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