Effect of tDCS on Memory in Older and Younger Adults
Conditions
Keywords
Transcranial Direct Current Stimulation, Memory, Prefrontal Cortex
Brief summary
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
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.
Interventions
DEVICEActive tDCS
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.
DEVICESham tDCS
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.
Sponsors
National Institute on Aging (NIA)
University of Chicago
Study design
Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
BASIC_SCIENCE
Masking
DOUBLE (Subject, Investigator)
Masking description
Neither the participant, nor the research assistant administering tDCS will know if the participant is receiving active tDCS or sham tDCS.
Eligibility
Sex/Gender
ALL
Age
18 Years to 75 Years
Healthy volunteers
Yes
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.
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Episodic Memory Performance | This task is performed immediately after tDCS is administered, and lasts approximately 20 minutes. | 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 the proportion of studied items attributed to the correct source minus the proportion of nonstudied items incorrectly attributed to that same source. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Working Memory Performance | 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). | 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. |
Countries
United States
Participant flow
Pre-assignment details
Participants have the right to end their participation at any time. In addition, the PI may terminate participation if a participant is in obvious non-compliance with the study procedures (e.g., responding randomly or sleeping during the cognitive task) or shows signs of moderate or severe adverse events associated with the study procedures (e.g., excessive discomfort with the tDCS electrodes). Enrolled participants may not continue in the study if they meet any of our exclusion criteria.
Participants by arm
| Arm | Count |
|---|---|
| Older, Active tDCS, dlPFC 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\.
Active tDCS: 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. | 46 |
| Older, Sham tDCS, dlPFC 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).
Sham tDCS: 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. | 45 |
| Younger, Active tDCS, dlPFC 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).
Active tDCS: 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. | 51 |
| Younger, Sham tDCS, dlPFC/Parietal 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).
Sham tDCS: 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. | 51 |
| Younger, Active tDCS, Parietal Cortex 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).
Active tDCS: 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. | 48 |
| Total | 241 |
Baseline characteristics
| Characteristic | Older, Active tDCS, dlPFC | Older, Sham tDCS, dlPFC | Younger, Active tDCS, dlPFC | Younger, Sham tDCS, dlPFC/Parietal | Younger, Active tDCS, Parietal Cortex | Total |
|---|---|---|---|---|---|---|
| Age, Categorical <=18 years | 0 Participants | 0 Participants | 0 Participants | 0 Participants | 0 Participants | 0 Participants |
| Age, Categorical >=65 years | 46 Participants | 45 Participants | 0 Participants | 0 Participants | 0 Participants | 91 Participants |
| Age, Categorical Between 18 and 65 years | 0 Participants | 0 Participants | 51 Participants | 51 Participants | 48 Participants | 150 Participants |
| Age, Continuous | 67.56 years STANDARD_DEVIATION 4.58 | 67.06 years STANDARD_DEVIATION 4.61 | 20.80 years STANDARD_DEVIATION 2.9 | 20.90 years STANDARD_DEVIATION 3.23 | 21.40 years STANDARD_DEVIATION 3.06 | 39.54 years STANDARD_DEVIATION 3.68 |
| Ethnicity (NIH/OMB) Hispanic or Latino | 3 Participants | 1 Participants | 9 Participants | 11 Participants | 14 Participants | 38 Participants |
| Ethnicity (NIH/OMB) Not Hispanic or Latino | 40 Participants | 38 Participants | 41 Participants | 38 Participants | 34 Participants | 191 Participants |
| Ethnicity (NIH/OMB) Unknown or Not Reported | 3 Participants | 6 Participants | 1 Participants | 2 Participants | 0 Participants | 12 Participants |
| Race (NIH/OMB) American Indian or Alaska Native | 0 Participants | 0 Participants | 0 Participants | 0 Participants | 0 Participants | 0 Participants |
| Race (NIH/OMB) Asian | 0 Participants | 0 Participants | 12 Participants | 17 Participants | 10 Participants | 39 Participants |
| Race (NIH/OMB) Black or African American | 22 Participants | 22 Participants | 7 Participants | 2 Participants | 5 Participants | 58 Participants |
| Race (NIH/OMB) More than one race | 5 Participants | 1 Participants | 6 Participants | 1 Participants | 4 Participants | 17 Participants |
| Race (NIH/OMB) Native Hawaiian or Other Pacific Islander | 0 Participants | 0 Participants | 0 Participants | 0 Participants | 0 Participants | 0 Participants |
| Race (NIH/OMB) Unknown or Not Reported | 0 Participants | 0 Participants | 2 Participants | 2 Participants | 2 Participants | 6 Participants |
| Race (NIH/OMB) White | 19 Participants | 22 Participants | 24 Participants | 29 Participants | 27 Participants | 121 Participants |
| Region of Enrollment United States | 46 participants | 45 participants | 51 participants | 51 participants | 48 participants | 241 participants |
| Sex: Female, Male Female | 31 Participants | 29 Participants | 30 Participants | 31 Participants | 27 Participants | 148 Participants |
| Sex: Female, Male Male | 15 Participants | 16 Participants | 21 Participants | 20 Participants | 21 Participants | 93 Participants |
Adverse events
| Event type | EG000 affected / at risk | EG001 affected / at risk | EG002 affected / at risk | EG003 affected / at risk | EG004 affected / at risk |
|---|---|---|---|---|---|
| deaths Total, all-cause mortality | 0 / 49 | 0 / 45 | 0 / 54 | 0 / 52 | 0 / 51 |
| other Total, other adverse events | 49 / 49 | 45 / 45 | 54 / 54 | 52 / 52 | 47 / 51 |
| serious Total, serious adverse events | 0 / 49 | 0 / 45 | 0 / 54 | 0 / 52 | 0 / 51 |
Outcome results
Primary
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 the proportion of studied items attributed to the correct source minus the proportion of nonstudied items incorrectly attributed to that same source.
Time frame: This task is performed immediately after tDCS is administered, and lasts approximately 20 minutes.
Population: Cognitively-normal adults.
| Arm | Measure | Value (MEAN) | Dispersion |
|---|---|---|---|
| Older, Active tDCS, dlPFC | Episodic Memory Performance | 0.34 proportion of items | Standard Deviation 0.25 |
| Older, Sham tDCS, dlPFC | Episodic Memory Performance | 0.32 proportion of items | Standard Deviation 0.25 |
| Younger, Active tDCS, dlPFC | Episodic Memory Performance | 0.46 proportion of items | Standard Deviation 0.26 |
| Younger, Sham tDCS, dlPFC/Parietal | Episodic Memory Performance | 0.50 proportion of items | Standard Deviation 0.23 |
| Younger, Active tDCS, Parietal Cortex | Episodic Memory Performance | 0.49 proportion of items | Standard Deviation 0.24 |
Secondary
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.
Time frame: 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).
Population: cognitively-normal adults
| Arm | Measure | Value (MEAN) | Dispersion |
|---|---|---|---|
| Older, Active tDCS, dlPFC | Working Memory Performance | 0.60 proportion of items | Standard Deviation 0.31 |
| Older, Sham tDCS, dlPFC | Working Memory Performance | 0.60 proportion of items | Standard Deviation 0.3 |
| Younger, Active tDCS, dlPFC | Working Memory Performance | 0.60 proportion of items | Standard Deviation 0.26 |
| Younger, Sham tDCS, dlPFC/Parietal | Working Memory Performance | 0.58 proportion of items | Standard Deviation 0.25 |
| Younger, Active tDCS, Parietal Cortex | Working Memory Performance | 0.60 proportion of items | Standard Deviation 0.26 |