HD-tDCS Over the dACC in High Trait Impulsivity

Study Overview
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Brief Summary
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Psychological disorders characterized by impulsivity often show alterations in dorsal anterior cingulate cortex (dACC) activity. Recent research has therefore focused on non-invasive neurostimulation therapies for the modulation of functional activity in the dACC. To date there has only been one proof-of-concept study providing evidence for modulating dACC activity with non-invasive electrical neurostimulation (e.g. transcranial electrical stimulation). Since transcranial Direct Current Stimulation (tDCS) is relatively safe, tolerable, and mobile as compared to other neurostimulation techniques, it is worthwhile looking further into the effects of tDCS on functional dACC activity. The aim of the present research is to explore whether HD-tDCS can induce changes in the dACC in individuals with high trait impulsivity (N=20) in a double-blind cross-over study. Functional changes in dACC activity will be measured by the error related negativity (ERN), which is an event related potential generated by the dACC. The ERN is less pronounced in people that score high on impulsivity. It is therefore expect enhanced ERN amplitudes after HD-tDCS over the dACC. In addition, performance on the multisource interference task will be used as measure of dACC activity. It is hypothesize that increased dACC activity will be related to decreased impulsivity in high impulsive individuals as shown by improved inhibitory control on the Go/NoGo task. The results of the study may have implications for patient populations that are characterized by impulsivity.

Official Title
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HD-tDCS Over the dACC in High Trait Impulsivity

Conditions
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Impulsive Behavior

Intervention / Treatment
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* Device: Active High Definition transcranial Direct Current Stimulation (HD-tDCS)
* Device: Sham High Definition transcranial Direct Current Stimulation (HD-tDCS)


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Right-handed Score > 46 on SUPPS-P Exclusion Criteria: Score low on trait impulsivity as determined by a score of < 47 on the SUPPS-P short form History of DSM-5 defined neurological illness, mental illness or traumatic brain injury, Currently taking any psychoactive medications, Have metal anywhere in the head, except the mouth. This includes metallic objects such as screws, plates and clips from surgical procedures. Currently pregnant or lactating, Being left-handed

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 55 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: Device Feasibility
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Double


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Active HD-tDCS<br> | Device: Active High Definition transcranial Direct Current Stimulation (HD-tDCS)<br>* TDCS is a non-invasive neuromodulation technique that modulates membrane potentials by means of small electrical currents. Electrical currents induced by tDCS electrodes produce an electrical field that modulates the excitability of brain areas. In the present HD-tDCS montage, one anodal electrode and four return electrodes are applied. Hereby, the anodal electrode modulates the excitability of the targeted area, whereas the other 4 electrodes return electrical currents that flow away from that area. Direct currents will be transmitted through 5 circular PiStim electrodes of 3.14cm2 (Neuroelectrics, Barcelona, Spain; current density=0.32 mA/cm2) with a current intensity of 1.5 mA. The HD-tDCS session will last for 20 minutes in total, with a 60 sec ramp at the beginning and end of the session. The electrodes will be filled with conductive gel and plugged into an EEG cap, with the anode placed over Fz and the four return electrodes over Fp1, Fp2, F7, and F8 (10-20 system).<br>|
| Sham Comparator: Sham HD-tDCS<br> | Device: Sham High Definition transcranial Direct Current Stimulation (HD-tDCS)<br>* For the sham-condition, the placement of the electrodes was identical to active HD-tDCS stimulation with the anode placed over Fz and the four return electrodes over Fp1, Fp2, F7, and F8 (10-20 system). The direct current, also transmitted through 5 circular PiStim electrodes of 3.14cm2 (Neuroelectrics, Barcelona, Spain; current density=0.32 mA/cm2), was increased in a ramp-like fashion over 60 seconds until it reached 1.5 mA. Directly after ramp-up, the current intensity was gradually switched off over 60 seconds, followed by 20 minutes without active stimulation. Sham procedures for tDCS mimic the transient skin sensation at the beginning of active HD-tDCS, without producing any conditioning effects on the brain. Consequently, participants are reliably blinded for sham tDCS.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in error related negativity (ERN) measured by electroencephalography (EEG) after active and sham HD-tDCS | To measure changes in electrophysiological measures of error processing after active vs. sham HD-tDCS | Baseline, directly after (active vs. sham) HD-tDCS, and 30 min after (active vs. sham) HD-tDCS. | 
| Change in NoGo N2 measured by electroencephalography (EEG) | To measure changes in electrophysiological measures of early inhibitory control processes after active vs. sham HD-tDCS | Baseline, directly after (active vs. sham) HD-tDCS, and 30 min after (active vs. sham) HD-tDCS. | 
| Change in NoGo P3 measured by electroencephalography (EEG) after active and sham HD-tDCS | To measure changes in electrophysiological measures of motor inhibitory control processes after active vs. sham HD-tDCS | Baseline, directly after (active vs. sham) HD-tDCS, and 30 min after (active vs. sham) HD-tDCS. | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in percentage of correct nogo trials on Go/NoGo task after active vs. sham HD-tDCS | To measure the effect of active vs. sham HD-tDCS on accuracy on trials for which responses have to be inhibited. Represents a measure of change in inhibitory control. | Baseline, directly after (active vs. sham) HD-tDCS, and 30 min after (active vs. sham) HD-tDCS. | 
| Change in reaction times on Go trials during Go/NoGo task after active vs. sham HD-tDCS | To measure changes in speed of motor responses during Go/NoGo task differences after active vs. sham HD-tDCS | Baseline, directly after (active vs. sham) HD-tDCS, and 30 min after (active vs. sham) HD-tDCS. | 
| Change in reaction times post incorrect trials during Go/NoGo task after active vs. sham HD-tDCS | To measure the effect of active vs. sham HD-tDCS on post-error slowing as behavioural measure of error processing. | Baseline, directly after (active vs. sham) HD-tDCS, and 30 min after (active vs. sham) HD-tDCS. | 
| Change in interference effect on multisource interference task (MSIT) after active vs. sham HD-tDCS | The interference effect is calculated by subtracting the mean reaction time for congruent trials from the mean reaction time for incongruent trials. A larger interference effect reflects worse performance and is suggested to reflect decreased dACC activity. | Baseline, directly after (active vs. sham) HD-tDCS, and 30 min after (active vs. sham) HD-tDCS. | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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ERN, Impulsivity, HD-tDCS, dACC, Go/NoGo, MSIT