Representations of semantic relations in the human cerebral cortex

An essential aspect of human cognition is the ability to explicitly think about semantic relations between concepts. Neuroimaging studies have found that individual concepts are encoded by distributed patterns of cortical activity, but relatively little is known about how semantic relations between concepts are encoded in the brain. Some theoretical models suggest that relation representations are embedded within concept representations, while others suggest that relation representations are independent of any specific concept pair. We designed a study to compare how semantic relations and concepts are encoded across the cerebral cortex. To characterize how relations are encoded across cortex, fMRI was used to record brain activity while six participants each answered over one thousand questions about different semantic relations. We find that relations are encoded independently of the specific concepts that are connected in any particular instance of the relation. Our results further suggest that relations and concepts are represented in the same set of cortical regions, and that, within these regions, each location is preferentially selective for specific relations. Overall, these results suggest that in the human cerebral cortex, relations and concepts may have the same type of functional representation.