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ObjectiveProcessing Speed (PS), the ability to perceive and react fast to stimuli in the environment, has been shown to be impaired in children with attention deficit hyperactivity disorder (ADHD). However, it is unclear whether PS can be improved following targeted treatments for ADHD. Here we examined potential changes in PS following application of transcranial electric stimulation (tES) combined with cognitive training (CT) in children with ADHD. Specifically, we examined changes in PS in the presence of different conditions of mental fatigue.MethodsWe used a randomized double-blind active-controlled crossover study of 19 unmedicated children with ADHD. Participants received either anodal transcranial direct current stimulation (tDCS) over the left dorsolateral prefrontal cortex (dlPFC) or transcranial random noise stimulation (tRNS), while completing CT, and the administration order was counterbalanced. PS was assessed before and after treatment using the MOXO-CPT, which measures PS in the presence of various conditions of mental fatigue and cognitive load.ResultstRNS combined with CT yielded larger improvements in PS compared to tDCS combined with CT, mainly under condition of increased mental fatigue. Further improvements in PS were also seen in a 1-week follow up testing.ConclusionThis study provides initial support for the efficacy of tRNS combined with CT in improving PS in the presence of mental fatigue in pediatric ADHD.

Various methods have been attempted to effectively ameliorate psychiatric and neurological conditions in children and adults. One of the attractive ideas is to develop interventions to create a lasting, rather than only an immediate, effect. Neurostimulation has been shown to yield long-term effect when combined with cognitive training in healthy young adults. We examined whether such approach could benefit children with attention deficit hyperactivity disorder (ADHD), the most common neurodevelopmental disorder in childhood. We used a randomized double-blind active-controlled crossover study of 19 unmedicated children (aged 7-12 years old) with attention deficit hyperactivity disorder, who received either transcranial direct current stimulation or random noise stimulation while completing five-day executive functions training, which includes working memory, cognitive flexibility, and inhibition tasks. Both stimulation protocols have previously shown potential for inducing lasting benefits in adults, while transcranial direct current stimulation was examined in multiple attention deficit hyperactivity disorder studies and has been highlighted as a promising method for treating neuropsychological deficits. For our primary outcome, transcranial random noise stimulation yielded a clinical improvement as indicated by the reduced attention deficit hyperactivity disorder rating scale score from baseline, and in comparison to the changes observed in transcranial direct current stimulation. Moreover, the effect of brain stimulation one week after completion of treatment yielded further improvement, suggesting a neuroplasticity-related effect. Finally, transcranial random noise stimulation improved working memory compared to transcranial direct current stimulation, and a larger transcranial random noise stimulation effect on attention deficit hyperactivity disorder rating scale was predicted for those patients who showed the greatest improvement in working memory. Our results provide a promising direction toward a novel intervention in attention deficit hyperactivity disorder, which is shown to have a lasting effect via the modulating of neuroplasticity, rather than a merely immediate effect as was shown for in previous medical interventions.

Non-invasive brain stimulation has been suggested as a potential treatment for improving symptomology and cognitive deficits in Attention-Deficit/Hyperactivity Disorder (ADHD), the most common childhood neurodevelopmental disorder. Here, we examined whether a novel form of stimulation, high-frequency transcranial random noise stimulation (tRNS), applied with cognitive training (CT), may impact symptoms and neural oscillations in children with ADHD. We conducted a randomized, double-blind sham-controlled trial in 23 unmedicated children with ADHD, who received either tRNS over the right inferior frontal gyrus (rIFG) and left dorsolateral prefrontal cortex (lDLPFC) or sham stimulation for 2 weeks, combined with CT. tRNS + CT yielded significant clinical improvements (reduced ADHD rating-scale scores) following treatment, compared to the control intervention. These improvements were maintained at a 3-week follow-up. Moreover, resting state (RS)-EEG periodic beta bandwidth of the extracted peaks was reduced in the experimental compared to control group immediately following treatment, with further reduction at follow-up. A marginally lower aperiodic exponent which reflects a higher excitation/inhibition was seen in the experimental compared to control group. The experimental group further exhibited longer sleep onset latencies and more wake-up times following treatment compared to the control group. No significant group differences were seen in executive functions, nor in reported adverse events. We conclude that tRNS + CT has a lasting clinical effect on ADHD symptoms and on beta activity. These results provide a promising direction towards a novel intervention in paediatric ADHD that induces sustained effects.

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