The Neural Consequences of Semantic Composition

Humans can create completely new concepts through semantic composition. These "conceptual combinations" can be created by attributing the features of one concept to another (e.g., a "lemon flamingo" might be a yellow flamingo) or drawing on a relationship between concepts (e.g., a "lemon flamingo" might consume lemons). We ask how semantic composition modulates the neural representations of underlying concepts. Combining fMRI with multivariate pattern analysis, we interrogate neural patterns for concepts before and after they were subjected to semantic composition. We observe a postcomposition shift in neural patterns underlying weakly constrained concepts in the visual system. The composition of strongly constrained combinations draws on a network of semantic regions that include the right inferior frontal gyrus, left angular gyrus, left lateral anterior temporal lobe, and posterior cingulate cortex. Finally, a subset of the semantic network, in the left parahippocampal gyrus, distinguishes the manner of composition: relational or attributive. These findings reveal that semantic composition has neural consequences for the composed concepts and that the manner of composition affects how the brain's semantic network is deployed.