Spontaneous and Explicit Mentalizing in Adults with Autism Spectrum Disorder: An Fmri Study

Background:

The socio-communicative difficulties of individuals with autism spectrum disorder (ASD) are hypothesized to be caused by a specific deficit in the ability to represent one’s own and others’ mental states, referred to as Theory of Mind or mentalizing. However, many individuals with ASD show successful performance on explicit measures of mentalizing, and for this reason, the deficit is thought to be specific to spontaneous mentalizing. While there is initial behavioral support for this hypothesis, spontaneous mentalizing in ASD has not yet been studied at the neural level. Recent findings in neurotypicals indicate a crucial role for the right temporoparietal junction (rTPJ) in both explicit and spontaneous mentalizing.

Objectives:

The goal of the current study was to investigate brain activation during both explicit and spontaneous mentalizing in adults with ASD and a neurotypical control group, by means of fMRI. Based on our hypothesis of a core mentalizing deficit in ASD associated with rTPJ abnormalities, decreased rTPJ activity was expected for both forms of mentalizing in adults with ASD.

Methods:

A group of 24 adults with ASD and 21 neurotypical controls carried out a spontaneous and an explicit version of the same mentalizing task. They watched videos in which both they themselves and another agent formed a belief about the location of an object (belief formation phase). Only in the explicit task version participants were instructed to report the agent’s belief on some trials.

Results:

At the behavioral level, no group differences were revealed in either of the task versions. A planned region-of-interest analysis of the rTPJ showed that this region was more active for false- than for true-belief formation, independent of task version, especially when the agent’s belief had a positive content (when the agent was expecting the object). This effect of belief was absent in adults with ASD. A whole-brain analysis revealed reduced activation in the anterior middle temporal pole in ASD for false- versus true-belief trials, independent of task version.

Conclusions:

Our findings suggest neural differences between adults with ASD and neurotypical controls both during spontaneous and explicit mentalizing, and indicate the rTPJ to be crucially involved in ASD. Moreover, the possible role of the anterior middle temporal pole in disturbed mentalizing in ASD deserves further attention. The finding that these neural differences do not necessarily lead to differential performance warrants further research.