Cortical Dynamics of Inhibitory Control: A Concurrent tDCS-MEG Study

Study Overview
=================
Brief Summary
-----------------
This study aims to use concurrent Transcranial Direct Current Stimulation (tDCS) and Magnetoencephalography (MEG) with measures of impulsivity to examine the neurobiological underpinnings of rapid response impulsivity (RRI) and how these can be modified using tDCS in healthy subjects.

Detailed Description
-----------------
Concurrent tDCS-MEG parallel arms single-blinded experimental design (right anodal v sham tDCS) will be employed in this study. The study will be conducted at the University of Nottingham, using a sample of student volunteers. This study aims to examine the influence of anodal tDCS on beta-band and alpha-band oscillatory activities, using an anti-saccade task administered before, during and after tDCS stimulation. It can potentially help understand the neurobiological mechanisms underpinning rapid response impulsivity and how these can be influenced by tDCS. The research hypotheses are that (i) a generalised mechanism for top-down inhibitory control will play a vital role, whereby prefrontal beta-band activity initiates alpha-band activity for functional inhibition over the frontal eye fields and other areas in the neurocircuitry involved in RRI; (ii) anodal tDCS (as opposed to sham) delivered over the right DLPFC will enhance this mechanism; and (iii) there will be no significant correlations between measures of self-report impulsivity and performance on the anti-saccade task and measures of oscillatory activity.

Official Title
-----------------
Measuring Cortical Dynamics of Inhibitory Control Before, During and After Transcranial Direct Current Stimulation (tDCS)

Conditions
-----------------
Impulsive Behavior

Intervention / Treatment
-----------------
* Device: Anodal tDCS
* Device: Sham tDCS


Participation Criteria
=================
Eligibility Criteria
-----------------
Inclusion Criteria: University students and staff Aged 18-40 Exclusion Criteria: Individuals with epilepsy and other neurological conditions, history of significant head injury, substance misuse, major mental disorder and those receiving psychotropic medication. Contraindications to use of Magnetic Resonance (pacemakers, metal implants, aneurysm clips) Pregnancy.

Ages Eligible for Study
-----------------
Minimum Age: 18 Years
Maximum Age: 40 Years

Sexes Eligible for Study
-----------------
All

Accepts Healthy Volunteers
-----------------
Accepts Healthy Volunteers

Study Plan
=================
How is the study designed?
-----------------

Design Details

Primary Purpose: Treatment
Allocation: Randomized
Intervention Model: Parallel Assignment
Interventional Model Description: Concurrent tDCS-MEG parallel arms single-blinded experimental design (right anodal v sham tDCS).
Masking: Single


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Anodal tDCS<br>The anodal tDCS electrode will be placed over the area corresponding to the right DLPFC (F4 of the EEG10-20 international system). The anodal tDCS condition will use a constant current of 2mA, delivered via gradual increase and decrease over 10 seconds at the onset and offset of stimulation (current ramps), respectively. | Device: Anodal tDCS<br>* The experimental condition will use a constant current of 2mA for 20 minutes, delivered via gradual increase and decrease over 10 seconds at the onset and offset of stimulation (current ramps), respectively.<br>|
| Sham Comparator: Sham tDCS<br>The sham (cathodal) electrode will be placed over the left supraorbital ridge. The current will be delivered only in the first 10 seconds, after which the stimulation will cease but with the electrodes still in place throughout the session. | Device: Sham tDCS<br>* The anodal electrode will be placed over the supreorbital ridge. The current will be delivered only in the first 10 seconds, after which the stimulation will cease but with the electrodes still in place throughout the session. The session will last for 20 minutes.<br>|

What is the study measuring?
-----------------
Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Total number of correct anti-saccade (AS) trials | A measure of rapid response impulsivity (inhibitory control) | Change from baseline after 20 minutes of tDCS | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Total number of correct pro-saccade (PS) trials | A behavioral measure of rapid response impulsivity (inhibitory control) | Change from baseline after 20 minutes of tDCS | 
| Saccade latency for anti-saccade (AS) trials | A behavioral measure of rapid response impulsivity (inhibitory control) | Change from baseline after 20 minutes of tDCS | 
| Saccade latency for pro-saccade (PS) trials | A behavioral measure of rapid response impulsivity (inhibitory control) | Change from baseline after 20 minutes of tDCS | 
| Total Scores on the UPPS+P Impulsive Behaviour Scale | A self-report measure of impulsivity | Baseline | 
| Alpha and Beta band activity | A Cortical measure of inhibitory control recorded using Magnetoencephalography (MEG). MEG is a brain imaging technique. | Change from baseline after 20 minutes of tDCS |