Dissertations, Theses, and Capstone Projects

Date of Degree


Document Type


Degree Name



Cognitive Neuroscience


Elizabeth Chua

Committee Members

Tony Ro

Robert Duncan

Subject Categories

Cognitive Science | Neuroscience and Neurobiology


Non-Invasive Brain Stimulation, HD-tDCS, tDCS, metamemory, memory, feeling-of-knowing


Metamemory is broadly defined as the awareness of one’s memory and consists, in part, of a process referred to as monitoring, where one is assessing the contents of their memory. Feeling of knowing (FOK) is one metamemory monitoring judgment where one rates how strongly they believe they will remember a currently unrecalled item. Prior work has shown that HighDefinition Transcranial Direct Current Stimulation (HD-tDCS) over the dorsal lateral prefrontal cortex (DLPFC) led to greater metamemory accuracy and that HD-tDCS over the anterior temporal lobe (ATL) led to better recall for medium difficulty questions. Other work has also shown that effects of tDCS are modulated by task difficulty and whether stimulation is online or offline. We investigated the effects of HD-tDCS over the left ATL, left DLPFC, and Sham conditions on memory and metamemory while manipulating recognition task difficulty and the timing of stimulation. There were no effects of stimulation on recognition. In terms of FOK ratings, there were higher FOK ratings in the ATL condition compared to DLPFC and Sham. There was also an effect of timing on FOK ratings, where rated FOK higher during offline stimulation, but this did not vary by stimulation condition. In terms of metamemory accuracy, stimulation over the DLPFC improved metamemory accuracy compared to ATL stimulation, but only in the easy condition. Overall, our results indicate the importance of task difficulty and timing when evaluating the effects of HD-tDCS on cognitive tasks.