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

Repetitive Behavior Scale-Revised

The primary outcome measure will be the Total Score of the Repetitive Behavior Scale-Revised (Bodfish, 2000). It consists of a 43-item parent-report questionnaire evaluating the extent of RBs in individuals with ASD. The tool encompasses six scales: Stereotyped Behavior (6 items), Self-injurious Behavior (8 items), Compulsive Behavior (8 items), Routine Behavior (6 items), Sameness Behavior (11 items), and Restricted Behavior (4 items). The items are rated on a four-point scale (0-Behavior does not occur, 1-Behavior occurs and is a mild problem, 2-Behavior occurs and is a moderate problem, 3-Behavior occurs and is a severe problem); an overall total raw score and a total number of items score for each subscale are computed. Higher scores indicate greater severity of repetitive behaviors. The sum of all items provides a total raw score ranging from 0 to 129, with higher scores indicating more severe repetitive behaviors.

Wisconsin Card Sorting Test

The version of the Wisconsin Card Sorting Test for developmental stages evaluates executive functions. The Modified Card Sorting Test (MCST; Nelson, 1976) assesses executive functions in children aged 4-13 years. It requires assigning 48 cards, on which one to four symbols are printed in different colors and shapes. The sorting rule (number, shape, color) changes after six correct assignments. The participant must deduce the current rule from the own pattern of responses. The number of right and wrong assignments and the number of errors will be computed.

Stop Signal Task

The Stop Signal Task is a computerized task evaluating inhibitory control. The task is structured in line with the consensus guide of SST (Verbruggen et al., 2019) and it will be performed on PsychoPy® software (Open Science Tools Ltd., Nottingham, UK). The task duration will be approximately 14 minutes. The Stop Signal Task will yield the following measures: stop signal reaction time, calculated in milliseconds by subtracting a mean Stop Signal Delays from the observed mean reaction times in no-stop trials; go accuracy; go reaction times; Stop Signal Delay.

Short Sensory Profile 2

The Short Sensory Profile 2 (Dunn, 2014) is a parent report questionnaire for evaluating the sensory processing pattern in children aged 3-14 years. It contains 34 items. Scores are assigned on a five-point Likert scale and range from "always = 0" to "often = 1" to "sometimes = 2" to "rarely = 3" to "never = 4". Low scores are indicative of frequent dysfunctional behavior. Based on a bell curve normed distribution, the raw score total for each quadrant can be classified as "much less than others" (lower 2%), "less than others" (between 1 SD and 2 SD below the mean, accounting for 14% of the normative sample), "just like the majority of others" (± 1 SD from the mean and accounting for 68% of the normative sample), "more than others" (between 1 SD and 2 SD above the mean), and "much more than others" (upper 2%).

Behavior Rating Inventory of Executive Function - Second Edition/ parent report

The Behavior Rating Inventory of Executive Function (Gioia et al., 2015) is a parent report questionnaire consisting of 63 items for an ecological and comprehensive evaluation of executive functions in children aged 5-18 years. The tool encompasses 63 items evaluating inhibition, self-monitoring, shift, initiation, working memory, emotional control, planning, task-monitoring, and organization of materials. Items are further dived into 4 indices as follows: the Behavior Regulation Index, the Emotion Regulation Index, the Cognitive Regulation Index, and the Global Executive Composite. Raw scores of each scale and index are converted into T scores (M = 50, SD = 10) and percentiles. For all clinical scales and indices, T scores from 60 to 64 and from 65 to 69 are considered respectively mildly elevated and potentially clinically elevated while T scores at or above 70 are clinically significant.