The application of high-definition tdcs in children and adolescents with autism spectrum disorder: a study protocol for a randomized, double-blind, sham-controlled clinical trial

Abstract Repetitive Behaviours (RBs) are a prevalent feature of ASD, comprising a heterogeneous group of symptoms. Multiple studies described two subgroups of RBs: a) lower-order (e.g., motor stereotypies and sensory seeking behaviours) and higher-order RBs (e.g., restricted interests and adherence to routines). These symptoms interfere with child functioning and learning opportunities, affecting the ability to engage socially. At a neurofunctional level, RBs have been related with diffuse brain alterations involving two distinct cerebral loops: i) a sensory-motor loop including sensory-motor cortex and its descent and ascendant projections to putamen; ii) an associative loop including dorsolateral prefrontal cortex (dlPFC) and its descent and ascendant projections to caudate. Considering that evidence-based treatment for RBs are still not available, new brain-based approaches are urgently needed. In recent years, non-invasive neuromodulation is providing promising evidence in improving clinical and neurocognitive symptoms in individuals with ASD. This study protocol aims to provide the scientific foundation for a 10-session High-Definition tDCS (HD-tDCS) treatment to reduce RBs in children and adolescents with ASD. Fifty-four participants will be randomly assigned to 3 conditions: 1) Frontal Group (active cathodal HD-tDCS over left dlPFC); 2) Pre-supplementary motor area (pre-SMA) Group (active cathodal HD-tDCS over pre-SMA cortex); 3) Sham Group (sham tDCS over dlPFC or pre-SMA cortex). The Repetitive Behavior Scale-Revised, as well as psychopathological, neuropsychological, and neurophysiological measures will be collected immediately before, immediately after, and three months after the end of the intervention. We hypothesise that active stimulation conditions will induce a reduction in RBs, and that the nature of RBs affected will depend on the stimulation site, with the Frontal Group improving in high-order RBs and the Pre-SMA Group in low-order RBs. The present study could prompt to identify innovative evidence-based treatment for individuals with ASD and contribute to deeper understand the RBs’ neurobiological basis. Research Category and Technology and Methods Clinical Research: 9. Transcranial Direct Current Stimulation (tDCS) Keywords: Autism Spectrum Disorder, Repetitive Behaviours , High-Definition tDCS, Randomized Clinical Trial