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

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

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.

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.

Participants will be randomly allocated, using a computer generated code, to receive either anodal tDCS or sham. For sham stimulation, 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 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.

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.

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.

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.

A Cortical measure of inhibitory control recorded using Magnetoencephalography (MEG). MEG is a brain imaging technique.

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.