The Role of Frontal Cortex in Object and Action Naming: a TMS Study

The lexical-semantic processing occurs at the left temporal neocortex and the action-related word processing occurs at left dorsolateral prefrontal cortex. One critical question is whether these neurological correlates of nouns and verbs are motivated by conceptual differences, or the grammatical disjunction between verbs and nouns. In the current study, we examine whether transcranial magnetic stimulation (TMS) on the left frontal speech area would inhibit only verb production if this is a place for verbs as a grammatical class, or would inhibit both noun and verb production, if it is a place for all action-related words. We found-out for the first time that, TMS induced facilitation rather than inhibition. This facilitation appeared as accuracy scores increased for action naming, when TMS was applied to the left frontal language region - compared to the vertex sham condition. The accuracy scores for object naming, as well as reaction times for both action and object naming were not affected by stimulation. Right hemisphere stimulation didn’t indicate of any effect.