Combining concepts across categorical domains: a linking role of the precuneus.

The human capacity for semantic knowledge entails not only the representation of single concepts but the capacity to combine these concepts into the increasingly complex ideas that underlie human thought. This process involves not only the combination of concepts from within the same semantic category but frequently the conceptual combination across semantic domains. In this fMRI study (N=24) we investigate the cortical mechanisms underlying our ability to combine concepts across different semantic domains. Using five different semantic domains (People, Places, Food, Objects and Animals), we present sentences depicting concepts drawn from a single semantic domain as well as sentences that combine concepts from two of these domains. Contrasting single-category and combined-category sentences reveals that the precuneus is more active when concepts from different domains have to be combined. At the same time, we observe that distributed category selectivity representations persist when higher-order meaning involves the combination of categories and that this category-selective response is captured by the combination of the single categories composing the sentence. Collectively, these results suggest that the combination of concepts across different semantic domains is mediated by the precuneus, which functions to link together category-selective representations distributed across the cortex.