Predication Drives Verb Cortical Signatures

Verbs and nouns are fundamental units of language, but their neural instantiation remains poorly understood. Neuropsychological research has shown that nouns and verbs can be damaged independently of each other, and neuroimaging research has found that several brain regions respond differentially to the two word classes. However, the semantic-lexical properties of verbs and nouns that drive these effects remain unknown. Here we show that the most likely candidate is predication: a core lexical feature involved in binding constituent arguments (boy, candies) into a unified syntactic-semantic structure expressing a proposition (the boy likes the candies). We used functional neuroimaging to test whether the intrinsic "predication-building" function of verbs is what drives the verb-noun distinction in the brain. We first identified verb-preferring regions with a localizer experiment including verbs and nouns. Then, we examined whether these regions are sensitive to transitivity--an index measuring its tendency to select for a direct object. Transitivity is a verb-specific property lying at the core of its predication function. Neural activity in the left posterior middle temporal and inferior frontal gyri correlates with transitivity, indicating sensitivity to predication. This represents the first evidence that grammatical class preference in the brain is driven by a word's function to build predication structures.