Non-invasive Brain Stimulation for Pediatric ADHD

Stimulation would be applied using semi-dry 5X5 cm electrodes. The current would be 0.75mA, which based on previous computational modeling of tDCS in children and is estimated to equal that of 1-1.5 mA in adults. This decision was made after considering the parameters that would influence current distribution and density at the site of stimulation such as thinner scalp, less cerebrospinal fluid, and smaller head size of the paediatric population. A similar dosage using tDCS was well tolerated by children, and was not associated with adverse effects29. The anodal electrode will be positioned above the dlPFC (F3 based on the International 10-20 system, while the cathodal electrode would be placed over the right supraorbital.

Children in the active tRNS group will received 0.75mA of tRNS (100-640Hz) to their left dorsolateral prefrontal cortex (dlPFC) and the right inferior frontal gyrus (IFG) via semi-dry 5cm X 5cm electrodes, attached under designated electrode positions (F3, F8) of a tES cap that followed the International 10-20 system (InnoSphere Inc., Haifa). The left dlPFC and right IFG were chosen, based on their contribution in executive control and inhibition. tRNS will be applied for 20 minutes per session during an iPad cognitive training. Similar duration has also been used in paediatrics using tDCS29. Similar to a previous tRNS study in children, and the rational provided for tDCS we will apply 0.75mA.

For sham-tRNS we will use the same montage as in active tRNS. For sham-tDCS we will use the same montage as in active tDCS. The only difference between active and sham tES would be that in the case of the sham tES the 30 sec of ramp up of the current from 0 to 0.75mA would not be followed by 19 min of stimulation at 0.75mA as in active tES, but would immediately be followed by 30 sec ramp down period to 0mA. Such method has been shown to provide effective blindness of the stimulation condition as both active and sham tES would lead to slight itching sensation that would disappear due scalp habitation. No further stimulation would be provided in the sham group during the daily session.