Modulation of reward positivity and blink rate in children with attention deficit hyperactivity disorder (ADHD) during and following transcranial direct current stimulation

Transcranial direct current stimulation (tDCS) over the right pre-frontal cortex has been found to increase striatal dopaminergic activity and modulate dopaminergic dependent behavior. However, it remains to be elucidated to what extent this tDCS set-up is effective in changing reward system activation in children and adolescents with attention-deficit/hyperactivity disorder (ADHD). Twenty-four children and adolescents with ADHD received both, 2 mA and sham tDCS. The anode was positioned over the ventromedial prefrontal-cortex (PFC), while the cathode was placed over the right dorsolateral PFC. During and after tDCS, participants performed an effort allocation task aimed at earning monetary rewards. Concurrent with task performance, the reward positivity (RewP) and blink rate were assessed using electroencephalography and eye tracking. Both markers may be influenced by striatal dopamine levels. We found an increase in RewP after tDCS compared to sham (b = 0.65; p = 0.010), but no significant difference during stimulation. No significant differences were found for tDCS-related changes in blink rate during or after stimulation. tDCS with an anode over the vmPFC and cathode over the rDLPFC increases RewP after stimulation in children and adolescents with ADHD, which may be related to tDCS effects on reward processing.