Thinking about the thoughts of others; temporal and spatial neural activation during false belief reasoning

•The ToM network is active from 150 to 400 ms in false compared to true beliefs.•False belief understanding evokes activation in the rTPJ from 150 to 225 ms.•ToM activity is first parietal (rTPJ and precuneus), then frontal (rIFG and SFG).•False belief requires executive processes that are not invoked in true belief.

Theory of Mind (ToM) is the ability to understand the perspectives, mental states and beliefs of others in order to anticipate their behaviour and is therefore crucial to social interactions. Although fMRI has been widely used to establish the neural networks implicated in ToM, little is known about the timing of ToM-related brain activity. We used magnetoencephalography (MEG) to measure the neural processes underlying ToM, as MEG provides very accurate timing and excellent spatial localization of brain processes. We recorded MEG activity during a false belief task, a reliable measure of ToM, in twenty young adults (10 females). MEG data were recorded in a 151 sensor CTF system (MISL, Coquitlam, BC) and data were co-registered to each participant's MRI (Siemens 3T) for source reconstruction. We found stronger right temporoparietal junction (rTPJ) activations in the false belief condition from 150 ms to 225 ms, in the right precuneus from 275 ms to 375 ms, in the right inferior frontal gyrus from 200 ms to 300 ms and the superior frontal gyrus from 300 ms to 400 ms. Our findings extend the literature by demonstrating the timing and duration of neural activity in the main regions involved in the “mentalizing” network, showing that activations related to false belief in adults are predominantly right lateralized and onset around 100 ms. The sensitivity of MEG will allow us to determine spatial and temporal differences in the brain processes in ToM in younger populations or those who demonstrate deficits in this ability.