The neural correlates of linguistic distinctions: unaccusative and unergative verbs

Unaccusative verbs like fall are special in that their sole argument is syntactically generated at the object position of the verb rather than at the subject position. Unaccusative verbs are derived by a lexical operation that reduces the agent from transitive verbs. Their insertion into a sentence often involves a syntactic movement from the object to the subject position. To explore the neurological reality of the distinction between different verb types and to identify the cortical activations associated with the lexical and syntactic operations, we compared unaccusative verbs with verbs that do not undergo such operations--unergatives (verbs with one argument, an agent) and transitives (verbs with two arguments). The observed pattern of activation revealed that the brain distinguishes between unaccusative and unergative verbs, lending neurological support for the linguistic distinction. A conjunction analysis between the comparisons between unaccusatives and the other verb types revealed activations in the left inferior frontal gyrus and the left posterior middle temporal gyrus. These, together with previous neuroimaging results, suggest that the inferior frontal gyrus may be involved with the execution of the syntactic operation, whereas the middle temporal gyrus may be responsible for the lexical operation that derives unaccusative verbs.