Reduced connectivity between mentalizing and mirror systems in autism spectrum condition

Abstract

The mentalizing system and mirror system are thought to play important roles in inferring the internal mental states of others - a process known as mentalizing. Autism spectrum condition (ASC) is associated with difficulties in mentalizing. The aim of this study was to determine whether the behavioural difficulties in mentalizing associated with ASC can be explained by changes in functional connectivity between the mentalizing and mirror system. We recruited 40 adult participants (20 with ASC and 20 typically-developing). Brain activity was monitored using functional magnetic resonance imaging while participants watched videos in which actors performed hand actions. The videos were shown in separate mentalizing and non-mentalizing blocks. During mentalizing blocks, participants were asked to indicate whether hand actions were clumsy or spiteful (i.e. to judge the intent of the action). During non-mentalizing blocks, participants indicated whether the actions were successful or unsuccessful (i.e. to judge the outcome of the action). Higher activity during the mentalizing blocks compared to non-mentalizing blocks was found in regions associated with the mentalizing system: the dorsal medial prefrontal cortex (dmPFC) and the temporo-parietal junction (TPJ), as well as in regions typically associated with the mirror system: the inferior frontal gyrus (IFG) and the inferior parietal lobe (IPL). Next, functional connectivity between regions was evaluated as a function of task. During mentalizing blocks, there was increased functional connectivity between the dmPFC and the mirror system in typically developing participants. In contrast, there was no increase in functional connectivity between these regions in ASC participants. Connectivity between the dmPFC and IFG was negatively correlated with autistic traits. The reduced connectivity in ASC participants was consistent with behavioural performance on the mentalizing task, which was also negatively correlated with the level of autistic traits. Together, these data emphasise the importance of functional connectivity between the mentalizing and mirror systems when inferring social intentions and show that reduced connectivity between these systems may explain some of the behavioural difficulties experienced by adults with ASC.