The role of dominant premotor cortex in language: a study using intraoperative functional mapping in awake patients

Although the role of the premotor cortex (PMC) was widely studied in motor function, very few data are currently available about the participation of this structure in language. We report a series of 25 right-handed patients harboring a low-grade glioma near or within the left dominant PMC, operated on under local anesthesia with intraoperative real-time sensorimotor and language mappings using electrical stimulations all along the resection. Language tasks consisted of counting and picture naming (preceded by the reading of a short sentence). Stimulations of the left PMC induced transient speech disturbances in all patients, with disruption of both counting and reading/naming during stimulation of the ventral PMC--due to elicitation of an anarthria--while generating an anomia during stimulation of the dorsal PMC. Moreover, corresponding subcortical pathways generated the same language disorders as at the cortical level when stimulated. Eloquent structures were systematically preserved, allowing the avoidance of definitive postoperative deficit. These findings suggest first that the left dominant PMC seems to play a major role in language and second that this structure could have a well-ordered functional organization, namely with the ventral PMC, which might be involved in planification of articulation, and the dorsal PMC, which might be involved in the naming network.