Familiarity modulates the functional relationship between theory of mind and autobiographical memory.

Qualitative and quantitative reviews of the neuroimaging literature show that overlapping brain regions support theory of mind (ToM) and autobiographical memory (AM). This overlap has been taken to suggest that individuals draw on past personal experiences to infer others' mental states, but work with amnesic people shows that ToM does not always depend on AM. One variable that may determine the extent to which one relies on AM when inferring another's thoughts and feelings during ToM is whether that individual is personally known. To test this possibility, participants were scanned with fMRI as they remembered past experiences in response to personal photos ('AM' condition) and imagined others' experiences in response to photos of personally familiar ('pToM' condition) and unfamiliar ('ToM' condition) others. Spatiotemporal Partial Least Squares was used to identify the spatial and temporal characteristics of neural activation patterns associated with AM, pToM, and ToM. We found that the brain regions supporting pToM more closely resembled those supporting AM relative to ToM involving unfamiliar others, with the greatest degree of overlap within midline regions. A complementary finding was the observation of striking differences between pToM and ToM such that midline regions associated with AM predominated during pToM, whereas more lateral regions associated with social semantic memory predominated during ToM. Overall, this study demonstrates that ToM involves a dynamic interplay between AM and social semantic memory that is biased towards AM when a personally familiar other is the subject of the mental state inference.