tES Effects on Associative Memory Performance

Study Overview
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Brief Summary
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Previous studies showed that transcranial electric stimulation (tES) applied over the prefrontal cortex improves cognitive performance in healthy elderly adults as well as in patients suffering from mild cognitive impairment or early Alzheimer's disease. Therefore, tES methods might be a useful intervention tool for patients suffering from memory impairment in early terms of the disease. The present study aims at establishing a connection between the stimulation-induced changes on associative memory performance and its underlying neurophysiological parameters. tES effects and their underlying mechanisms will be compared between healthy elderly controls and clinical study populations receiving either real or sham tES over the left ventrolateral prefrontal cortex during an associative memory task.

Official Title
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Effects of Transcranial Electric Stimulation on Associative Memory Formation in Healthy Elderly Participants as Well as in Individuals With Memory Impairment

Conditions
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Healthy, Mild Cognitive Impairment, Alzheimer Disease

Intervention / Treatment
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* Device: real anodal transcranial direct current stimulation
* Device: real transcranial alternating current stimulation
* Device: sham transcranial electric current stimulation


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Written informed consent Non-smokers Right-handedness Native German speakers or comparable level of fluency Normal or corrected-to-normal vision Exclusion Criteria: Neurological or psychiatric condition (other than diagnosed cognitive impairment) Past head injuries Magnetizable implants History of seizures Current or life-time alcohol or drug abuse Skin diseases

Ages Eligible for Study
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Minimum Age: 60 Years
Maximum Age: 85 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: Double


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Real tDCS<br>20 min of 2 mA real anodal transcranial direct current stimulation applied via 5x7 cm rubber electrode over the VLPFC (current density: 0.057 mA/cm2) and cathodal 10x10 rubber electrode over supraorbital region (current density: 0.02 mA/cm2). Additional ramp-up and ramp-down phase of 15 s at the beginning and the end of stimulation. | Device: real anodal transcranial direct current stimulation<br>* The MR-compatible neuroConn DC-Stimulator MR (neuroCare Group, Ilmenau, Germany) will be used.<br>|
| Experimental: Real tACS<br>20 min of 2 mA real transcranial alternating current stimulation in theta frequency applied via 5x7 cm and 10x10 cm rubber electrodes over the VLPFC (current density: 0.057 mA/cm2) and supraorbital region (current density: 0.02 mA/cm2). Additional ramp-up and ramp-down phase of 15 s at the beginning and the end of stimulation. | Device: real transcranial alternating current stimulation<br>* The MR-compatible neuroConn DC-Stimulator MR (neuroCare Group, Ilmenau, Germany) will be used.<br>|
| Sham Comparator: Sham tES<br>30 s of 2 mA sham transcranial electric current stimulation applied via 5x7 cm and 10x10 cm rubber electrodes over the VLPFC (current density: 0.057 mA/cm2) and supraorbital region (current density: 0.02 mA/cm2). Additional ramp-up and ramp-down phase at beginning and end of stimulation lasting for 15 s. Electrodes remain attached to the participant's head for the duration of the encoding phase of the memory task. | Device: sham transcranial electric current stimulation<br>* The MR-compatible neuroConn DC-Stimulator MR (neuroCare Group, Ilmenau, Germany) will be used.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Performance on immediate cued recall task | Number of correct responses on retrieval task of previously learned associative memory items | 20 min | 
| Performance on delayed cued recall task | Number of correct responses on retrieval task of previously learned associative memory items | 24 hours | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| task-dependent BOLD activity | Measured with functional magnetic resonance imaging (fMRI) | 20 min | 
| resting-state BOLD activity | Measured with functional magnetic resonance imaging (fMRI) | 10 min |