Functional activity of the right temporo-parietal junction and of the medial prefrontal cortex associated with true and false belief reasoning

Since false belief reasoning requires mental state representation independently of the state of reality, it is seen as a key ability in Theory of Mind (ToM). Although true beliefs do not have to be processed independently of the state of reality, growing behavioural evidence indicates that true belief reasoning is different from just reasoning about the state of reality. So far, neural studies on true and false belief reasoning revealed inconsistent findings in the medial prefrontal cortex (MPFC) and in the right temporo-parietal junction (R-TPJ), brain regions that are hypothesized to play an important role in ToM. To further explore true and false belief reasoning, the present functional magnetic resonance imaging (fMRI) study in eighteen adult subjects used methodological refinements such as ensuring that the true belief trials did not elicit false belief reasoning, as well as including paralleled control conditions requiring reasoning about the state of reality. When compared to its control condition, common R-TPJ activity was observed for true and false belief reasoning, supporting its role in belief reasoning in general, and indicating that, at least in adults, also true belief reasoning appears to be different from reasoning about the state of reality. Differential activity was observed in a broad network of brain regions such as the MPFC, the inferior frontal cortex, and the precuneus. False over true belief reasoning induced activation in the posterior MPFC (pMPFC), supporting its role in the decoupling mechanisms, which is defined as processing a mental state independently of the state of reality.