HD-tDCS to Modulate Connectivity

Study Overview
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Brief Summary
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The purpose of the proposed study is to broaden our understanding on the neural effects of High Definition Transcranial Direct Current Stimulation (HD-tDCS) so that its clinical effects can be further improved.

Detailed Description
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Normal healthy individuals will be recruited and undergo a standardized neuropsychological assessment (ANAM, MoCA, BDI-II, ToMS, and MAAS) and magnetic resonance imaging (MRI). During MRI, HD-tDCS will be applied. Four different stimulation targets will be investigated, and subjects will be randomly assigned for each target groups or sham group. After HD-tDCS/MRI session, subjects will be re-assessed with standardized neuropsychological tests.

Official Title
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Modulating Functional Brain Connectivity Using High Definition Transcranial Direct Current Stimulation (HD-tDCS)

Conditions
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Electricity; Effects

Intervention / Treatment
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* Device: high definition transcranial direct current stimulation (HD-tDCS)


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: - All other than excluded. Exclusion Criteria: History or susceptibility to any neurological or psychiatric diseases, particularly seizures abnormal MRI metal implants or a cardiac pacemaker pregnant or breastfeeding women

Ages Eligible for Study
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Minimum Age: 18 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
Interventional Model Description: 4 active treatment groups + 1 inactive treatment group
Masking: Single


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: left DLPFC stimulation<br>HD-tDCS will be used to deliver direct current to the target via rubber electrodes and HD-tDCS gels. The 9 electrodes (8 channels + 1 ground) positions and current intensity will be determined based on computer simulation using HDTargets software (Soterix Inc.) that results in maximum focal current on the left dorsolateral prefrontal cortex (DLPFC; x=-44, y=10, z=30) with inward field orientation. The peak current will not exceed 2 mA. A constant current will be delivered for 20 minutes. | Device: high definition transcranial direct current stimulation (HD-tDCS)<br>* HD-tDCS will be provided for 20 minutes for each stimulation with peak intensity of 2mA.<br>|
| Experimental: right DLPFC stimulation<br>HD-tDCS will be used to deliver direct current to the target via rubber electrodes and HD-tDCS gels. The 9 electrodes (8 channels + 1 ground) positions and current intensity will be determined based on computer simulation using HDTargets software (Soterix Inc.) that results in maximum focal current on the right dorsolateral prefrontal cortex (DLPFC; x=+42, y=+14, z=+30) with inward field orientation. The peak current will not exceed 2 mA. A constant current will be delivered for 20 minutes. | Device: high definition transcranial direct current stimulation (HD-tDCS)<br>* HD-tDCS will be provided for 20 minutes for each stimulation with peak intensity of 2mA.<br>|
| Experimental: left IPL stimulation<br>HD-tDCS will be used to deliver direct current to the target via rubber electrodes and HD-tDCS gels. The 9 electrodes (8 channels + 1 ground) positions and current intensity will be determined based on computer simulation using HDTargets software (Soterix Inc.) that results in maximum focal current on the left intraparietal lobe (IPL; x=-50, y=-36, z=+42) with inward field orientation. The peak current will not exceed 2 mA. A constant current will be delivered for 20 minutes. | Device: high definition transcranial direct current stimulation (HD-tDCS)<br>* HD-tDCS will be provided for 20 minutes for each stimulation with peak intensity of 2mA.<br>|
| Experimental: VLPFC-PCC stimulation<br>HD-tDCS will be used to deliver direct current to the target via rubber electrodes and HD-tDCS gels. The 9 electrodes (8 channels + 1 ground) positions and current intensity will be determined based on computer simulation using HDTargets software (Soterix Inc.) that results in maximum focal current on the left ventrolateral prefrontal cortex (VLPFC; x=-50, y=+26, z=+8) and posterior cingulate cortex (PCC; x=1, y=-61, z=38) with inward field orientation. The peak current will not exceed 2 mA. A constant current will be delivered for 20 minutes. | Device: high definition transcranial direct current stimulation (HD-tDCS)<br>* HD-tDCS will be provided for 20 minutes for each stimulation with peak intensity of 2mA.<br>|
| Sham Comparator: Sham stimulation<br>One of the above three targets will be randomly selected. The current will be applied for 30 seconds ramp-up followed by 30 seconds ramp-down. | Device: high definition transcranial direct current stimulation (HD-tDCS)<br>* HD-tDCS will be provided for 20 minutes for each stimulation with peak intensity of 2mA.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| change of functional connectivity | Changes in seed-based connectivity originating from the targeted brain regions immediately after the brain stimulation | 0-11 minutes after the stimulation contrasting baseline (before stimulation) | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| change of cerebral blood flow | Changes in Cerebral Blood Flow (estimated using pseudo continuous arterial spin labeling ) | 12-16 minutes after the stimulation contrasting baseline (before stimulation) | 
| Toronto Mindfulness Scale (curiosity) | mindfulness scale for curiosity. min: 0, max: 30. Higher score means higher curiosity-mindfulness. | Baseline, then within 1-2 hours from stimulation | 
| Toronto Mindfulness Scale (decentering) | mindfulness scale for decentering. min: 0, max: 35. Higher score means higher decentering-mindfulness. | Baseline, then within 1-2 hours from stimulation |