Theta-Burst Stimulation of the Right Temporoparietal Junction and Implicit Theory of Mind in Autism

Background: Theory of mind (ToM) or mentalizing, is the ability to attribute mental states to oneself and others and is altered in individuals with autism spectrum disorder (ASD). Recent evidence suggest that implicit, rather than explicit ToM is impaired in individuals with ASD. The right temporoparietal junction (rTPJ), which plays a crucial role in ToM, has altered activity in ASD and can be targeted by noninvasive brain stimulation. Methods: In a randomized double-blind placebo-controlled study, we investigated for the first time the effects of theta-burst stimulation of the rTPJ on implicit ToM and egocentric bias in seventeen adolescents with ASD. Participants (mean age = 13.84±3.32) were randomly assigned to three sessions each of continuous theta-burst stimulation (cTBS), intermittent theta-burst stimulation (iTBS), and sham stimulation. Stimulation intensity was set to 80% of the active motor threshold during cTBS and iTBS, with the coil centered on the rTPJ (CP6). Immediately after each stimulation, cognitive correlates of ToM, including implicit mentalizing and egocentric bias, were evaluated using the computerized Buzz-lightyear task. Results: Our results show that both cTBS and iTBS significantly improved implicit ToM in participants as compared to sham stimulation, with cTBS being more effective than iTBS. No effect of stimulation was, however, found on the egocentric bias index. Conclusions: These findings demonstrate a causal link between the rTPJ activation and implicit mentalizing in ASD, suggesting that theta-burst stimulation of this region can be used to enhance ToM in ASD. Targeting the rTPJ may improve implicit mentalizing in ASD and other disorders with impaired ToM.