Non-invasive Brain Stimulation for Pediatric ADHD

External influences on neuroplastic processes may be used for functional improvement of diseases, in particular for improving cortical functions. The possibility of influencing brain activity and steadily enhancing behavioral performance through external intervention has long fascinated neuroscientists. One of these techniques, transcranial electrical stimulation (tES), has received great interest because it has great potential use in basic research and clinical applications. Transcranial electrical stimulation (tES) in the current research includes two types of stimulation: transcranial direct current stimulation (tDCS) and transcranial random noise stimulation (tRNS). The tES techniques involve the application of constant weak direct current (e.g. 1-2 mA) to the brain via skin-electrode interface, creating electric field that modulates neuronal activity. This modulation is polarity dependent toward depolarization after anodal stimulation (excitatory) and toward hyperpolarization after cathodal stimulation (inhibitory), leading to transient changes in the resting membrane potential. The cumulative effect of longer stimulation results in a polarity-dependent facilitation or inhibition of the spontaneous neuronal firing rate and is considered neuromodulatory.

tDCS, provokes a sub-threshold modulation of neuronal excitability without depolarizing action potentials5. Post stimulation effects of tDCS depends on the duration of stimulation (lasting from several minutes up to hours) and can be found in the areas under the electrodes and also remote by network changes.

The mechanism by which tRNS influences brain activity differs from tDCS. The delivery of tRNS uses the same equipment as for tDCS. In tRNS, however, both electrodes can be used to stimulate either in homologous locations bilaterally or at different regions simultaneously. tRNS can be used to stimulate a region with a current that varies randomly in time. Such stimulation can induce excitability that lasts up to 60 minutes per 10 minutes of stimulation1. The most beneficial type of tRNS is at high-frequency (100-640Hz).

This is a randomized, double blinded, placebo-controlled, crossover study in ADHD children. Eligible participants will be randomized into the 3 following groups:

1. tDCS-placebo (sham) group to receive either tDCS or matching placebo (sham( during 5 following days (one session each day). After a one week break, there will be a crossover between the control group and the sham group: those we received tDCS in the 1st week will get sham, while those who received sham in the 1st week will received tDCS at the 3rd week.
2. tRNS-sham group, who will receive the same type of intervention with the same intervals as above but with tRNS instead of tDCS.
3. tDCS-tRNS group. Here the same intervention as above will be provided with the same intervals, but real tDCS and real tRNS will be provided in a counterbalanced fashion. This would allow to compare the different treatment in a within-subject design, as well as to compare the effect of those to sham stimulation in the first two groups in a between-subject design.