Contribution of the right temporoparietal junction and ventromedial prefrontal cortex to theory of mind in autism: A randomized, sham‐controlled tDCS study

Abstract

Theory of Mind (ToM) is the ability to attribute subjective mental states to oneself and others and is significantly impaired in Autism Spectrum Disorder (ASD). A frontal-posterior network of regions including the ventromedial prefrontal cortex (vmPFC) and temporoparietal junction (TPJ) is involved in ToM. Previous studies show an underactivation of these regions in ASD.Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation method for causally investigating brain-behavior relationships via induction of cortical excitability alterations. tDCS, mostly over the dorsolateral prefrontal cortex, has been increasingly applied for improving behavioral problems in ASD leaving other potentially interesting regions untouched. Here we investigated the contribution of the vmPFC and right TPJ in ToM abilities of ASD children via tDCS in a pilot study. Sixteen children with ASD (mean age = 10.7±1.9) underwent three tDCS sessions (1 mA, 20 min) in a randomized, double-blind, sham-controlled design. Stimulation protocols included: i) anodal vmPFC tDCS, ii) anodal r-TPJ tDCS, and iii) sham tDCS. ToM abilities were explored during tDCS using the Theory of Mind Test (TOMT). Our results show that activation of the vmPFC with anodal tDCS significantly improved ToM in children with ASD compared to both, r-TPJ tDCS and sham stimulation. Specifically, precursors of ToM (e.g. emotion recognition, perception and imitation) and elementary ToM skills (e.g. first-order mental state reasoning) were significantly improved by anodal vmPFC tDCS. Based on these results, the vmPFC could be a potential target region for the reduction of ASD symptoms via non-invasive brain stimulation, which should be examined in larger detail in future studies.

A systematic review of randomized controlled trials on efficacy and safety of transcranial direct current stimulation in major neurodevelopmental disorders: ADHD, autism, and dyslexia

“…Two recent studies also reported improving effects of frontocerebellar tDCS (i.e., anodal left dlPFC, cathodal right cerebellar tDCS) on behavioral symptoms (Toscano et al., 2019 ), and anodal stimulation over the primary motor cortex on motor skill training in children with ASD (Mahmoodifar & Sotoodeh, 2020 ). Of 11 included studies, only 1 study targeted right TPJ and vmPFC, two key regions in the theory of mind in ASD, and found that anodal vmPFC, but not r‐TPJ tDCS, significantly improved ToM in children with ASD (Salehinejad et al., 2021 ).…”

“…In the last couple of years, however, tDCS has been increasingly used in children and adolescents (Rivera‐Urbina et al., 2017 ; Salehinejad et al., 2021 ; Vicario & Nitsche, 2013 , 2019 ). In child psychiatric disorders, tDCS has been mostly applied in neurodevelopmental disorders specifically attention‐deficit hyperactivity disorder (ADHD) (Salehinejad et al., 2021 , 2016 ; Westwood et al., 2021 ), autism spectrum disorder (ASD) (García‐Gonz ález et al., 2021 ; Osório & Brunoni, 2019 ), and developmental dyslexia (Salehinejad et al., 2021 ; Turker & Hartwigsen, 2022 ).…”

Are We Right about the Right TPJ? A Review of Brain Stimulation and Social Cognition in the Right Temporal Parietal Junction

“…Based on data collected in non-clinical populations, it has been speculated that modulation of the rTPJ may have an impact on classic socially related patient symptomology. For example, Transcranial direct stimulation (tDCS) delivered to the right TPJ has been shown to improve behavioral issues associated with ASD [120]. Due to the relationship of the TPJ with mental and emotional state attribution, with similar processes associated with autism-relevant traits, tDCS to the TPJ has the ability to influence social-cognitive performance [121].…”

“…The Salehinejad study, in detail, examined the role of both the vMPFC (ventral Medial Prefrontal Cortex) and the rTPJ implying tDCS [120]. They found a greater clinical role for the vMPFC which indicates that the rTPJ is far from the only site responsible for these complex disorders.…”

Multisession Anodal tDCS on the Right Temporo-Parietal Junction Improves Mentalizing Processes in Adults with Autistic Traits

“…An alternative technique is transcranial direct current stimulation (tDCS). Although tDCS has the significant drawback of offering much less focal stimulation than rTMS, it also has some advantages, such as having relatively long-lasting effects—about an hour after 12 min of stimulation [ 25 ]—a generally noticeable impact on performance and the possibility to use excitatory (anodal) or inhibitory (cathodal) stimulation [ 26 , 27 ]. In the social domain, the use of tDCS remains relatively limited, and to date, it has been mainly aimed at experimentally inducing changes in cognitive and social behavior in neurotypical individuals, to understand better the neural mechanisms of ToM.…”