Effect of Noninvasive Electrical Brain Stimulation on Memory at Different Times of Day in Younger and Older Adults

Study Overview
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Brief Summary
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This study will investigate the extent to which tDCS to dorsolateral prefrontal cortex (or dlPFC) impacts memory performance as a function of time-of-day in younger and older adults.

Detailed Description
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Transcranial Direct Current Stimulation (tDCS) is the safest and most accessible, non-invasive brain stimulation technique available for testing causal links between different brain regions and functions, by manipulating cognitive abilities. By identifying key experimental factors that can improve the reliability and robustness of stimulation effects on cognitive performance in different age groups, this project should lead to the widespread adoption of these design features in future applications. This study will investigate the extent to which tDCS to dorsolateral prefrontal cortex (or dlPFC) impacts recollection accuracy and working memory performance as a function of time-of-day in younger and older adults. Moreover, this study will test the extent that tDCS to dlPFC impacts memory performance by impacting information-specific processes and/or cognitive control processes that operate across different types of information, thereby informing basic theories of how dlPFC contributes to memory in younger and older adults.

Official Title
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Effect of Noninvasive Electrical Brain Stimulation on Memory Performance at Different Times of Day in Younger and Older Adults

Conditions
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Effect of tDCS on Memory in Older and Younger Adults

Intervention / Treatment
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* Device: Active tDCS
* Device: Sham tDCS


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Right-handed (according to the Edinburgh Handedness Inventory) Normal or corrected vision Fluent in English (started learning by age 6) Ability to understand and provide informed consent for study procedures, and to comply - with study procedures for the entire length of the study. For individuals in the 'younger adults' group, must be between 18 and 30 years of age For individuals in the 'older adults' group, must be between 60 and 75 years of age A score of 23 or above on the Montreal Cognitive Assessment (out of 30, education-corrected) is required. This is to minimize the inclusion of suspected mild cognitive impairment (MCI) or dementia, targeting individuals that score in the normal range according to the recent meta-analysis of MoCA's ability to differentiate normal aging from MCI in Carson et al. (2018, Int. J of Geriatric Psychiatry). Performance above threshold on the episodic memory task during the baseline session. The threshold is defined as having a hit rate that is at least 5% greater than the false alarm rate, where hit rate is defined as the number of studied items identified as studied, divided by the total number of studied items, and false alarm rate is defined as the number of new items identified as studied, divided by the total number of new items. We don't anticipate this threshold to exclude many, if any subjects. Exclusion Criteria: Neuropsychological conditions associated with cognitive decline or seizure Cochlear implants or metal in the brain/skull (except titanium) Psychoactive medications, or diagnosis of depression, bipolar disorder, or any psychotic diagnoses History of excessive use (clinically treated) alcohol or narcotics Hospitalization for head trauma (e.g. concussions) in the past 5 years Individuals above a threshold score on an assessment of depression, specifically, a score of 10 or above on the Patient Health Questionnaire (PHQ-9)(Manea et al., 2012) Risk of pregnancy Low tolerance of skin irritation Prior brain stimulation experience (self-report) Ongoing cognitive or sensory deficits/symptoms from a previous (or current) COVID-19 infection.

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 75 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: Parallel Assignment
Masking: Double


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Older, active tDCS, dlPFC<br>Older adults (ages 60-75) randomized to this arm will receive 2 sessions of active tDCS stimulation (Soterix Medical) delivered to the left dorsolateral prefrontal cortex. One session will occur in the morning (8 or 9am) and one will occur on a separate day in the afternoon (3 or 4pm). 2. | Device: Active tDCS<br>* The brain is stimulated for 20 minutes with mild electrical current (maximum 2 mA) with two 7 cm x 5 cm electrodes placed on the scalp, using a standard 1x1 tDCS Clinical Trials device (Soterix Medica, NY), specialized for double-blinding.<br>|
| Sham Comparator: Older, sham tDCS, dlPFC<br>Older adults (ages 60-75) randomized to this arm will receive 2 sessions of sham tDCS stimulation (Soterix Medical) delivered to the left dorsolateral prefrontal cortex. One session will occur in the morning (8 or 9am) and one will occur on a separate day in the afternoon (3 or 4pm). | Device: Sham tDCS<br>* The brain is not stimulated for 20 minutes with mild electrical current, but instead a sham procedure is administered using a standard 1x1 tDCS Clinical Trials device (Soterix Medica, NY), specialized for double-blinding.<br>|
| Experimental: Younger, active tDCS, dlPFC<br>Younger adults (ages 18-30) randomized to this arm will receive 2 sessions of active tDCS stimulation (Soterix Medical) delivered to the left dorsolateral prefrontal cortex. One session will occur in the morning (8 or 9am) and one will occur on a separate day in the afternoon (3 or 4pm). | Device: Active tDCS<br>* The brain is stimulated for 20 minutes with mild electrical current (maximum 2 mA) with two 7 cm x 5 cm electrodes placed on the scalp, using a standard 1x1 tDCS Clinical Trials device (Soterix Medica, NY), specialized for double-blinding.<br>|
| Sham Comparator: Younger, sham tDCS, dlPFC/parietal<br>Younger adults (ages 18-30) randomized to this arm will receive 2 sessions of sham tDCS stimulation (Soterix Medical) delivered to either the left dorsolateral prefrontal cortex (area F3 using the 10-20 EEG system, n = 25), or the left parietal cortex (area P5 using the 10-20 EEG system, n = 25). One session will occur in the morning (8 or 9am) and one will occur on a separate day in the afternoon (3 or 4pm). | Device: Sham tDCS<br>* The brain is not stimulated for 20 minutes with mild electrical current, but instead a sham procedure is administered using a standard 1x1 tDCS Clinical Trials device (Soterix Medica, NY), specialized for double-blinding.<br>|
| Active Comparator: Younger, active tDCS, parietal cortex<br>Younger adults (ages 18-30) randomized to this arm will receive 2 sessions of active tDCS stimulation (Soterix Medical) delivered to the left parietal cortex (area P5 using the 10-20 EEG system). One session will occur in the morning (8 or 9am) and one will occur on a separate day in the afternoon (3 or 4pm). | Device: Active tDCS<br>* The brain is stimulated for 20 minutes with mild electrical current (maximum 2 mA) with two 7 cm x 5 cm electrodes placed on the scalp, using a standard 1x1 tDCS Clinical Trials device (Soterix Medica, NY), specialized for double-blinding.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Episodic memory performance | To measure episodic memory performance, participants will perform a recollection task. They will first study picture and word stimuli (encoding phase). On the subsequent memory test (retrieval phase), participants will be asked to differentiate between studied and non-studied items, as well as recollecting the previous format for studied items (i.e. recollecting the picture or word). For each tested item, participants will also be asked to make a confidence judgement about their response. The primary dependent variable (DV) will be recollection accuracy: the proportion of correctly recollected studied items minus the non-studied item baseline. | This task is performed immediately after tDCS is administered, and lasts approximately 20 minutes. | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Working memory performance | To measure working memory performance, participants will perform two versions of the N-back task -- a verbal version (i.e., presenting the numbers 1-9 in a varied sequence) and a visuospatial version (i.e., presenting a colored square in one of 9 locations on a 3x3 grid in a varied sequence). The primary DV will be working memory accuracy: proportion of targets correctly identified minus the proportion of lures incorrectly endorsed. | This task lasts approximately 10 minutes and is performed immediately after the episodic memory task (approximately 20 minutes after the end of the tDCS session). | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Transcranial Direct Current Stimulation, Memory, Prefrontal Cortex