A discrete area within the left dorsolateral prefrontal cortex involved in visual-verbal incongruence judgment

The role of the frontal lobe in cross-modal visual-auditory processing has been documented in experiments using incongruent/congruent paradigms. In this study, 4 patients with left frontal World Health Organization Grade II glioma were assessed during pre-, intra-, and postoperative sessions with picture-naming and verbal-visual task requiring judgment of congruence between pictures and words. During awake brain surgery, the naming and cross-modal tasks were coupled with electrical stimulation inactivating restricted specific regions. For all patients, focal brain stimulation in the dorsolateral prefrontal cortex elicited picture-word matching disturbances but no naming impairment, and the elicited errors exclusively appeared in incongruent and not congruent conditions. The dissociation observed between correct picture naming and disturbed cross-modal judgment shows that electrical stimulation of a discrete cortical area within the left dorsolateral prefrontal cortex can inhibit the simultaneous processing of visual-verbal information without disturbing larger networks involved in the naming process.