The Effect of Different Intensities of Bilateral- and Cathodal-tDCS in Healthy Individuals

Study Overview
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Brief Summary
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This study will be divided into 2 sub-study 1) To investigate the effects of 1 mA, 1.5 mA, and 2 mA of bilateral- tDCS on cortical activity and motor/cognitive performances in healthy individuals 2) To investigate the effects of 1 mA, 1.5 mA, and 2 mA of cathodal-tDCS on cortical activity and motor/cognitive performances in healthy individuals.

Detailed Description
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Transcranial direct current stimulation (tDCS) is one of the non-invasive brain stimulation (NIBS) techniques. It delivers weak direct current through the scalp via two electrodes. tDCS has been shown to modulate cortical excitability in polarity-specific effects; anodal increases cortical excitability, while cathodal decreases it. tDCS can be applied in two distinct montages: unilateral (an active electrode is applied over the cerebral cortex, while a reference electrode is applied over the contralateral orbit) and bilateral-tDCS (applying two electrodes simultaneously over both cerebral hemispheres). Many tDCS studies have been used as an add-on therapy in stroke patients which aimed to enhance motor re-learning after stroke. Anodal tDCS has been used to enhance cortical excitability in the lesioned hemisphere while cathodal tDCS is used to decrease it in the non-lesioned hemisphere and thus to rebalance the interhemispheric inhibition (IHI). However, there were recent studies reporting the reverse effect of cathodal-tDCS on cortical excitability at high doses. However, the effects of cathodal-tDCS among different doses on cortical excitability and on motor performance are still controversial no report of a non-linear effect for bilateral-tDCS. The present study will be investigated the effects of different intensities of unilateral cathodal tDCS and bilateral tDCS on cortical activity and functional outcomes in healthy individuals. A single session of different intensities of bilateral-tDCS or cathodal-tDCS (i.e., 1 mA, 1.5 mA, 2 mA vs. sham) will be combined with serial reaction time task (SRTT) in healthy individuals. Cortical activity will be measured as a primary outcome. All power bands (alpha, beta, delta, theta) will be analyzed. Moreover, analysis of brain activity will be also focused on both hemispheres. The reaction time of serial reaction time task and muscle strength will be served as the secondary outcome. Cortical activity and muscle strength will be evaluated before and after the intervention, while reaction time will be evaluated during and after the intervention.

Official Title
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The Effect of Different Intensities of Bilateral- and Cathodal-transcranial Direct Current Stimulation (tDCS) on Cortical Activity and Motor Performances in Healthy Individuals

Conditions
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Healthy

Intervention / Treatment
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* Device: Bilateral-Transcranial direct current stimulation (bilateral-tDCS)
* Device: Cathodal-Transcranial direct current stimulation (cathodal-tDCS)
* Device: Sham bilateral-tDCS
* Device: Sham cathodal-tDCS


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: 1. Age 18-29 years old 2. Righ-hand dominant according to the Edinburgh handedness inventory 3. No injury to both upper and lower limb for the past 6 months Exclusion Criteria: 1. Presence of any neurological disorders 2. Presence of metal implantation, intracranial shunt, cochlear implantation, or cardiac pacemakers 3. Presence of opened wound or infectious wound around scalp 4. History of epilepsy or any neurological antecedent or unstable condition which can lead to seizure 5. Body mass index (BMI) > 30 kg/m2 6. Received hormonal treatment and/or drugs that increase sleepiness and affect movement control 7. Ischemic heart disease and peripheral vascular ischemia 8. Last stage of kidney disease and liver disease

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 29 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: Treatment
Allocation: Randomized
Intervention Model: Crossover Assignment
Interventional Model Description: The participants who will participate in one of two studies will be randomly received 1 mA or 1.5 mA or 2 mA or sham with the washout period for at least 2 weeks. The participants could not participate in both studies.
Masking: Triple


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Active Comparator: Active bilateral-tDCS<br>Participants will be received different intensities which are 1 mA, 1.5 mA and 2 mA for 20 minutes during performed serial reaction time task. The tDCS will be set with bilateral montage which applied anodal electrode over left hemisphere and cathodal electrode over right hemisphere. | Device: Bilateral-Transcranial direct current stimulation (bilateral-tDCS)<br>* The tDCS is non-invasive brain stimulation technique applied over the participant's scalp using a reference to the International 10-20 electrode Placement System for EEG electrode placement. The cathodal and anodal electrodes will be applied over the right and left primary motor areas, respectively.<br>* Other names: MINDD STIM; Ybrain Inc., Korea;|
| Sham Comparator: Sham bilateral-tDCS<br>Participants will be received sham of bilateral tDCS during performed serial reaction time task. | Device: Sham bilateral-tDCS<br>* Sham bilateral-tDCS<br>|
| Active Comparator: Active cathodal-tDCS<br>Participants will be received different intensities which are 1 mA, 1.5 mA and 2 mA for 20 minutes during performed serial reaction time task. The tDCS will be set with cathodal montage which applied cathodal electrode over left hemisphere and anodal over right orbit. | Device: Cathodal-Transcranial direct current stimulation (cathodal-tDCS)<br>* The tDCS is non-invasive brain stimulation technique applied over the participant's scalp using a reference to the International 10-20 electrode Placement System for EEG electrode placement. The cathodal electrode will be attached over the left primary motor area while the anodal will be applied over the right supraorbital.<br>* Other names: MINDD STIM; Ybrain Inc., Korea;|
| Sham Comparator: Sham cathodal-tDCS<br>Participants will be received sham of cathodal tDCS during performed serial reaction time task. | Device: Sham cathodal-tDCS<br>* Sham cathodal-tDCS<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Cortical activity | Acquired by electroencephalography (EEG) | 5 minutes | 
| The reaction time | Measured the reaction time from serial reaction time task | 30 minutes | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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tDCS, Cortical activity, Healthy, Motor performance, Cognitive