General and specific contributions of the medial prefrontal cortex to knowledge about mental states

Recent neuroimaging research (Mitchell, J.P., Heatherton, T.F., Macrae, C.N., 2002. Distinct neural systems subserve person and object knowledge. Proc. Natl. Acad. Sci. U. S. A. 99, 15238-15243.) has suggested that semantic knowledge about the psychological aspects of other people draws on a pattern of neural activity that differentiates social from nonsocial semantics. Although the medial prefrontal cortex (mPFC) clearly plays a central role in a range of such social-cognitive tasks, little is known about the precise contributions made by this region to social semantics. The current study addressed two outstanding questions regarding mPFC function. First, do mPFC contributions to processing words that refer to psychological states extend to other, nonhuman targets or are they specific to understanding the psychological experience of conspecifics? Second, does the mPFC respond generally to tasks that require processing another person, or is its activity specific to understanding psychological characteristics? To address these questions, participants were scanned using fMRI while judging the applicability of words to one of two types of targets: people or dogs. For each target, participants made one of two types of semantic judgment: does this word describe a potential psychological state of the target or does this word refer to a physical part of the target? Results demonstrated that greater mPFC activation accompanied judgments of psychological states than of body parts regardless of whether the target was a person or a dog, indicating that mPFC contributions to social semantics are specific for understanding psychological states--directly countering recent suggestions that mPFC responds generally to any judgment about another person--and that mPFC activity extends to targets other than conspecifics.