Effects of Brain-stimulation on Metamemory Monitoring and Control

Study Overview
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Brief Summary
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When people learn and remember information, it is often accompanied by a feeling of subjective confidence about whether or not information has been learned and accurately remembered. These subjective feelings of confidence are often related to actual memory performance, but are sometimes incorrect. The investigators have previously shown that applying high definition transcranial direct current stimulation (HD-tDCS) over the dorsolateral prefrontal cortex leads to more accurate feelings of subjective confidence, at least when subjects are asked for their confidence about future memory performance. Accurate confidence judgments are useful in that they may later subsequent behavior, and inaccurate ones may be costly. For example, a student who erroneously believes that studied material was learned may stop studying and not do well on a test. Individuals who have a feeling-of-knowing about the answer to a general knowledge question will continue to search their memory, whereas individuals who do not have a feeling-of-knowing will stop searching their memory. Individuals who are confident they know the answer to a question are more likely to answer it. In this study, the experimenters are testing the effects of brain stimulation on subjective awareness of memory (termed metamemory monitoring) and how people use those subjective judgments (termed metamemory control). The approach taken is to have participants visit the laboratory on 3 visits and receive brain stimulation while completing memory and metamemory tasks.

Official Title
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Effects of Brain-stimulation on Memory and Memory Awareness

Conditions
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Healthy

Intervention / Treatment
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* Device: HD-tDCS


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Healthy, right-handed adults ages 18-35. English spoken since age 5. Normal or corrected-to-normal vision. Exclusion Criteria: Participants will be excluded if they have chronic skin disease or a medical skin condition, or an unhealed open wound on the scalp, face, neck, or forehead near the electrode location. Participants will be excluded if they self-report significant medical, neurological, or psychiatric illness and/or a history of substance abuse

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 35 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Single


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Active DLPFC during task<br>HD-tDCS will be applied over the DLPFC at 2mA in a single session for up to 30 min during the memory and metamemory task | Device: HD-tDCS<br>* Participants will complete a metamemory and memory task<br>* Other names: Behavioral;|
| Active Comparator: Active DLPFC after task<br>HD-tDCS will be applied over the DLPFC at 2mA in a single session for up to 30 min after the memory and metamemory task and during a filler task. | Device: HD-tDCS<br>* Participants will complete a metamemory and memory task<br>* Other names: Behavioral;|
| Sham Comparator: Sham DLPFC during task<br>Sham HD-tDCS will be applied over the DLPFC at 2mA in a single session for up to 30 min during the memory and metamemory task | Device: HD-tDCS<br>* Participants will complete a metamemory and memory task<br>* Other names: Behavioral;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Memory Control Advantage Index | This indexes the memory advantage for choosing which general knowledge question one receives a hint about the answer to versus having the experimenter choose which general knowledge question one receives a hint about the answer. The investigators will subtract the proportion of correctly recognized general knowledge answers for experimenter-chosen questions from the proportion correctly recognized for participant-chosen questions | Through study completion, an average of 3 weeks | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| semantic recognition as assessed by a general knowledge task | Differences in recognition are compared between each condition (each active HD-tDCS and sham). | Through study completion, an average of 3 weeks | 
| semantic recall as assessed by a general knowledge task | Differences in recall are compared between each condition (each active HD-tDCS and sham). | Through study completion, an average of 3 weeks | 
| Feeling-of-knowing ratings and their accuracy | Feeling of knowing ratings are given on a scale. To assess the accuracy of these ratings, the subjective ratings are compared to objective accuracy, using signal detection based measures. Differences in feeling-of-knowing ratings and their accuracy are compared between each condition (each active HD-tDCS and sham). | Through study completion, an average of 3 weeks | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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memory, metacognition, metamemory, transcranial direct current stimulation