Introduction
Asia)Given, ADHD, Hyperactivity Disorder
CORTEX, BRAIN
In recent years, Non Invasive Brain Stimulation (NIBS) techniques and, in particular, transcranial Direct Current Stimulation (tDCS)Attention-Deficit Hyperactivity Disorder (ADHD) is one of the most prevalent neurodevelopmental conditions, which affects 5.9% of youth and 2.5% of adults (in America, Europe, Australia, and Asia)Given the concerns that drug-based treatments of ADHD have raised in the past, there is an ongoing search for treatments with reduced or no side effectsAs an exploratory study in preparation for the main clinical trial, a tDCS intervention in a healthy pediatric population has been designed to target 2 areas of interest: the left Dorsolateral Prefrontal Cortex (lDLPFC) and the right Inferior Frontal Gyrus (rIFG). TDCS is applied to each area of interest both while the participants are performing a task during the stimulation (concurrent task condition) and while the participants are at rest during the stimulation (non-concurrent task condition). Previous studies on tDCS were not conclusive enough about the need to have a concurrent task to increase the response effect of tDCSWe present a methodology for healthy participants’ stratification based on their profile of resting state EEG activity before the tDCS stimulation. The effect of the tDCS intervention on their performance in behavioral tasks performed after the tDCS stimulation is taken into account to label the resulting groups. The considered behavioral metrics correspond to Accuracy and Reaction Times of the Flanker, N-Back, and Continuous Performance Task (CPT) tasks. The performance effect is assessed as the difference in these metrics between the active and the sham conditions. In order to determine the baseline EEG profiles, we extracted spectral features that were found relevant in previous studies in pediatric EEG studiesInterestingly, the positive responder groups correspond to participants with a non-typical profile of EEG activity, presenting either a slowing of the EEG or a spread of increased alpha rhythm over frontal areas. Our methodology could be applied in the future to stratify patients for tDCS treatment, enabling to focus on those specific digital phenotypes in which tDCS is more likely to become effective. Personalization of treatment, i.e. applying tDCS only to groups of patients predicted to have positive results, would save costs, and time, and improve the efficacy of the treatment at lower sample sizes.