Targeting Repetitive Behaviors in Autism Spectrum Disorder Via Transcranial Direct Current Stimulation

Repetitive behaviors (RBs) are a prevalent feature of Autism Spectrum Disorder (ASD). There are two groups of RBs: lower-order (e.g. motor stereotypies) and higher-order RBs (e.g. restricted interests), linked to sensory-motor and the associative loops, respectively. To date, treatment options for RBs are very limited. High-definition transcranial direct current stimulation (HD-tDCS) may be effective in reducing the impact of RBs in children with ASD by targeting the associated brain alterations. Moreover, the high focality of HD-tDCS will help the investigators to disentangle the relative contribution of different brain loops (namely, sensory-motor and the associative loops) into RBs subtypes. The investigators will also study the electrophysiological patterns associated to behavioral changes after the application of HD-tDCS.

The experimental design will be the following: randomized, three-arm, between subject, double blind, and placebo-controlled.

Children and adolescents with ASD will be selected and randomly assigned to three groups: 1. Active high-definition tDCS (HD-tDCS) over pre-SMA; 2. Active high-definition tDCS (HD-tDCS) left DLPFC; 3. Sham high-definition tDCS (HD-tDCS).

In this project, the investigators will work to understand whether a brain-based intervention, with the use of HD-tDCS can enhance RBs in individuals with ASD.

The protocol will allow the investigators to:

1. Test if Active high-definition tDCS (HD-tDCS) compared to sham HD-tDCS will contribute in reducing RBs
2. Test if HD-tDCS over pre-SMA cortex will decrease lower-order RBs, while HD-tDCS over dlPFC will decrease higher-order RBs
3. Test if the Active Groups will significantly improve in the remaining psychological measures compared to the Sham Group
4. Test if the Active Groups will change in the RBS-R total score will be significantly correlated with changes in neuropsychological and electroencephalographic (EEG) connectivity measures
5. Test if the Active Groups will change in the RBS-R total score will be significantly correlated with changes in the remaining psychological measures and parental stress.

The overarching goal is to provide a scientific foundation for devising new rehabilitation strategies in ASD.

Eligibility Criteria:
Inclusion Criteria:

* participants of both genders with ASD diagnosis according to the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) and based on clinical evaluation and administration of gold standard tools for ASD diagnosis
* an intelligence quotient (IQ) higher or equal to 70 (IQ ≥ 70)
* age range from 8 years to 13 years and 11 months included

Exclusion Criteria:

* the presence of neurological/medical/genetic conditions (i.e., brain tumours or genetic syndromes)
* personal or family history of epilepsy
* other primary psychiatric diagnoses (i.e., bipolar disorders, schizophrenia spectrum disorders, or adjustment disorder)
* sensorimotor deficits
* the presence of peacemaker or other metal devices in the body;
* ongoing CNS-active drug treatment
* receiving other cognitive-behavioral therapies specifically focused on RBs in the 3 months before the study