| Abstract: | Language localization data from 11 neurosurgical patients undergoing cortical resection for medically intractable focal epilepsy were obtained by mapping with bipolar electrical stimulation at current levels below sensory and after-discharge thresholds, during an object-naming task. The topographical extent of language cortex in an individual subject can be wider than that proposed in the classic maps. Within this zone, language is discretely localized, with different sites variably committed to language as measured by the naming function. The naming data from the left cortex of eight patients, all left-brain-dominant, were pooled to determine the variability within the primary language zone. Only a narrow band of posterior, inferior frontal lobe, immediately anterior to motor strip, showed involvement in all of the patients in whom it was sampled. This is a motor speech area; it constitutes only a small portion of the frontal language area. Other infero-frontal, parietal, and postero-temporal sites showed considerable variability, with naming involvement in only 50–80% of the patients sampled. There is a suggestion that some of these patterns of language localization may correlate with poorer verbal abilities. Data were also obtained on language localization in the left insula in a patient who was left-hemisphere-dominant for language. Mapping of the right hemisphere in a left-brain-dominant patient demonstrated no naming function. Mapping of the right hemisphere in one and the left hemisphere in another patient, both of whom were right-hemisphere-dominant for language, suggests more diffuse language representation with right hemisphere dominance. |
