Defining the neural correlates of spontaneous theory of mind (ToM): An fMRI mega-analytic investigation
There is a major debate in the theory of mind (ToM) field, concerning whether spontaneous and explicit ToM are based on the same or two distinct cognitive systems. While there is extensive research on the neural correlates of explicit ToM, revealing consistent activation of the temporo-parietal junction (TPJ) and medial prefrontal cortex (mPFC), few studies investigated spontaneous ToM, with conflicting results, probably due to having small samples of participants. Here, we implemented a mega-analytic approach by pooling data from three fMRI studies, to achieve enough statistical power to better define the neurocognitive mechanisms underlying spontaneous ToM. Participants watched videos in which an agent acquires a true or false belief about the location of a ball. By analysing the blood-oxygen level dependent signal during the belief formation phase for false versus true beliefs, we found a cluster of activation in the right, and to a lesser extent, left posterior parietal cortex spanning the TPJ, but no mPFC activation. Region of interest (ROI) analysis on bilateral TPJ and mPFC confirmed these results and added evidence to the content-selectivity for false beliefs with positive content and asymmetry in laterality of the spontaneous ToM system. Interestingly, the whole brain analysis, supported by an overlap with brain maps, revealed maximum activation in areas involved in visuospatial working memory and attention switching functions, such as the supramarginal gyrus, the middle temporal gyrus, and the inferior frontal gyrus. Taken together, these findings suggest that spontaneous and explicit ToM rely on partially overlapping brain systems. However, spontaneous ToM tasks also show clear differences with explicit ToM tasks.