A stranger in my brain: Neural representation for unfamiliar persons using fMRI repetition suppression.

Prior neuroimaging research demonstrated that the ventromedial prefrontal cortex (vmPFC) houses neural representations for traits and familiar persons that possess these traits. But do such neural representations also exist for people we do not know? We hypothesized that knowledge about unknown persons is encoded in "generic" mentalizing representations as opposed to "specific" representations for well-known individuals. Neural representations for unfamiliar persons were investigated by fMRI repetition suppression, which is a rapid suppression of fMRI responses upon repeated presentation of the same stimulus signaling the neural representation of this stimulus. Participants had to infer an unfamiliar person's traits from brief behavioral descriptions. In each trial, a critical sentence was preceded by another sentence in which we manipulated whether or not the person or trait was repeated. The results revealed suppression for unfamiliar others in the vmPFC extending earlier research, as well as in novel areas including the inferior parietal lobule and dorsal posterior cingulate. We also found trait suppression in the vmPFC. This indicates that the vmPFC houses neural populations of "generic" representations of unknown persons and their traits. We speculate that the other brain areas showing suppression might reflect embodied representations at a somatomotor level.