Neuromodulation of verb-transitivity judgments

Abstract

This study aimed to further clarify the roles of the temporal and frontal lobes of the brain in the processing of verb argument structure. Left inferior frontal brain areas have long been considered important for sentence processing, but recent research links left posterior temporal cortex to knowledge of verb argument structure. We applied cathodal High-Definition transcranial Direct Current Stimulation to 45 participants in a between-subjects design, with 15 participants each for inferior-frontal-cortex stimulation, posterior-temporal-cortex stimulation, and sham stimulation. Set up as a training task during stimulation, participants made overt judgments on the number of participant roles associated with individual verbs. Stimulation of posterior temporal cortex did not yield results that were different from sham stimulation, speeding up task responses overall. By contrast, stimulation of inferior frontal cortex yielded differential results for intransitive versus transitive verbs, speeding up responses to intransitive verbs and increasing accuracy to transitive verbs, relative to other conditions. The transitivity effect, specific to inferior frontal stimulation, suggests a role for inferior frontal cortex in access to verb-argument-structure information, possibly specific to situations of high cognitive load and in which participant roles have to be established for production, as opposed to comprehension.